rfc9535.original   rfc9535.txt 
JSONPath WG S. Gössner, Ed. Internet Engineering Task Force (IETF) S. Gössner, Ed.
Internet-Draft Fachhochschule Dortmund Request for Comments: 9535 Fachhochschule Dortmund
Intended status: Standards Track G. Normington, Ed. Category: Standards Track G. Normington, Ed.
Expires: 27 March 2024 ISSN: 2070-1721
C. Bormann, Ed. C. Bormann, Ed.
Universität Bremen TZI Universität Bremen TZI
24 September 2023 February 2024
JSONPath: Query expressions for JSON JSONPath: Query Expressions for JSON
draft-ietf-jsonpath-base-21
Abstract Abstract
JSONPath defines a string syntax for selecting and extracting JSON JSONPath defines a string syntax for selecting and extracting JSON
(RFC 8259) values from a JSON value. (RFC 8259) values from within a given JSON value.
About This Document
This note is to be removed before publishing as an RFC.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology
1.1.1. JSON Values as Trees of Nodes . . . . . . . . . . . . 6 1.1.1. JSON Values as Trees of Nodes
1.2. History . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.2. History
1.3. JSON Values . . . . . . . . . . . . . . . . . . . . . . . 7 1.3. JSON Values
1.4. Overview of JSONPath Expressions . . . . . . . . . . . . 8 1.4. Overview of JSONPath Expressions
1.4.1. Identifiers . . . . . . . . . . . . . . . . . . . . . 8 1.4.1. Identifiers
1.4.2. Segments . . . . . . . . . . . . . . . . . . . . . . 8 1.4.2. Segments
1.4.3. Selectors . . . . . . . . . . . . . . . . . . . . . . 9 1.4.3. Selectors
1.4.4. Summary . . . . . . . . . . . . . . . . . . . . . . . 9 1.4.4. Summary
1.5. JSONPath Examples . . . . . . . . . . . . . . . . . . . . 11 1.5. JSONPath Examples
2. JSONPath Syntax and Semantics . . . . . . . . . . . . . . . . 12 2. JSONPath Syntax and Semantics
2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 12 2.1. Overview
2.1.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . 14 2.1.1. Syntax
2.1.2. Semantics . . . . . . . . . . . . . . . . . . . . . . 14 2.1.2. Semantics
2.1.3. Example . . . . . . . . . . . . . . . . . . . . . . . 15 2.1.3. Example
2.2. Root Identifier . . . . . . . . . . . . . . . . . . . . . 15 2.2. Root Identifier
2.2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . 16 2.2.1. Syntax
2.2.2. Semantics . . . . . . . . . . . . . . . . . . . . . . 16 2.2.2. Semantics
2.2.3. Examples . . . . . . . . . . . . . . . . . . . . . . 16 2.2.3. Examples
2.3. Selectors . . . . . . . . . . . . . . . . . . . . . . . . 17 2.3. Selectors
2.3.1. Name Selector . . . . . . . . . . . . . . . . . . . . 17 2.3.1. Name Selector
2.3.1.1. Syntax . . . . . . . . . . . . . . . . . . . . . 17 2.3.1.1. Syntax
2.3.1.2. Semantics . . . . . . . . . . . . . . . . . . . . 19 2.3.1.2. Semantics
2.3.1.3. Examples . . . . . . . . . . . . . . . . . . . . 20 2.3.1.3. Examples
2.3.2. Wildcard Selector . . . . . . . . . . . . . . . . . . 21 2.3.2. Wildcard Selector
2.3.2.1. Syntax . . . . . . . . . . . . . . . . . . . . . 21 2.3.2.1. Syntax
2.3.2.2. Semantics . . . . . . . . . . . . . . . . . . . . 21 2.3.2.2. Semantics
2.3.2.3. Examples . . . . . . . . . . . . . . . . . . . . 22 2.3.2.3. Examples
2.3.3. Index Selector . . . . . . . . . . . . . . . . . . . 23 2.3.3. Index Selector
2.3.3.1. Syntax . . . . . . . . . . . . . . . . . . . . . 23 2.3.3.1. Syntax
2.3.3.2. Semantics . . . . . . . . . . . . . . . . . . . . 23 2.3.3.2. Semantics
2.3.3.3. Examples . . . . . . . . . . . . . . . . . . . . 23 2.3.3.3. Examples
2.3.4. Array Slice selector . . . . . . . . . . . . . . . . 24 2.3.4. Array Slice Selector
2.3.4.1. Syntax . . . . . . . . . . . . . . . . . . . . . 24 2.3.4.1. Syntax
2.3.4.2. Semantics . . . . . . . . . . . . . . . . . . . . 24 2.3.4.2. Semantics
2.3.4.3. Examples . . . . . . . . . . . . . . . . . . . . 27 2.3.4.3. Examples
2.3.5. Filter selector . . . . . . . . . . . . . . . . . . . 28 2.3.5. Filter Selector
2.3.5.1. Syntax . . . . . . . . . . . . . . . . . . . . . 29 2.3.5.1. Syntax
2.3.5.2. Semantics . . . . . . . . . . . . . . . . . . . . 32 2.3.5.2. Semantics
2.3.5.3. Examples . . . . . . . . . . . . . . . . . . . . 34 2.3.5.3. Examples
2.4. Function Extensions . . . . . . . . . . . . . . . . . . . 39 2.4. Function Extensions
2.4.1. Type System for Function Expressions . . . . . . . . 39 2.4.1. Type System for Function Expressions
2.4.2. Type Conversion . . . . . . . . . . . . . . . . . . . 40 2.4.2. Type Conversion
2.4.3. Well-Typedness of Function Expressions . . . . . . . 41 2.4.3. Well-Typedness of Function Expressions
2.4.4. length() Function Extension . . . . . . . . . . . . . 42 2.4.4. length() Function Extension
2.4.5. count() Function Extension . . . . . . . . . . . . . 43 2.4.5. count() Function Extension
2.4.6. match() Function Extension . . . . . . . . . . . . . 43 2.4.6. match() Function Extension
2.4.7. search() Function Extension . . . . . . . . . . . . . 44 2.4.7. search() Function Extension
2.4.8. value() Function Extension . . . . . . . . . . . . . 44 2.4.8. value() Function Extension
2.4.9. Examples . . . . . . . . . . . . . . . . . . . . . . 45 2.4.9. Examples
2.5. Segments . . . . . . . . . . . . . . . . . . . . . . . . 46 2.5. Segments
2.5.1. Child Segment . . . . . . . . . . . . . . . . . . . . 47 2.5.1. Child Segment
2.5.1.1. Syntax . . . . . . . . . . . . . . . . . . . . . 47 2.5.1.1. Syntax
2.5.1.2. Semantics . . . . . . . . . . . . . . . . . . . . 47 2.5.1.2. Semantics
2.5.1.3. Examples . . . . . . . . . . . . . . . . . . . . 48 2.5.1.3. Examples
2.5.2. Descendant Segment . . . . . . . . . . . . . . . . . 48 2.5.2. Descendant Segment
2.5.2.1. Syntax . . . . . . . . . . . . . . . . . . . . . 48 2.5.2.1. Syntax
2.5.2.2. Semantics . . . . . . . . . . . . . . . . . . . . 49 2.5.2.2. Semantics
2.5.2.3. Examples . . . . . . . . . . . . . . . . . . . . 50 2.5.2.3. Examples
2.6. Semantics of null . . . . . . . . . . . . . . . . . . . . 52 2.6. Semantics of null
2.6.1. Examples . . . . . . . . . . . . . . . . . . . . . . 52 2.6.1. Examples
2.7. Normalized Paths . . . . . . . . . . . . . . . . . . . . 53 2.7. Normalized Paths
2.7.1. Examples . . . . . . . . . . . . . . . . . . . . . . 56 2.7.1. Examples
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 56 3. IANA Considerations
3.1. Registration of Media Type application/jsonpath . . . . . 56 3.1. Registration of Media Type application/jsonpath
3.2. Function Extensions . . . . . . . . . . . . . . . . . . . 57 3.2. Function Extensions Subregistry
4. Security Considerations . . . . . . . . . . . . . . . . . . . 59 4. Security Considerations
4.1. Attack Vectors on JSONPath Implementations . . . . . . . 59 4.1. Attack Vectors on JSONPath Implementations
4.2. Attack Vectors on How JSONPath Queries are Formed . . . . 59 4.2. Attack Vectors on How JSONPath Queries Are Formed
4.3. Attacks on Security Mechanisms that Employ JSONPath . . . 60 4.3. Attacks on Security Mechanisms That Employ JSONPath
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 60 5. References
5.1. Normative References . . . . . . . . . . . . . . . . . . 60 5.1. Normative References
5.2. Informative References . . . . . . . . . . . . . . . . . 61 5.2. Informative References
Appendix A. Collected ABNF grammars . . . . . . . . . . . . . . 62 Appendix A. Collected ABNF Grammars
Appendix B. Inspired by XPath . . . . . . . . . . . . . . . . . 66 Appendix B. Inspired by XPath
B.1. JSONPath and XPath . . . . . . . . . . . . . . . . . . . 67 B.1. JSONPath and XPath
Appendix C. JSON Pointer . . . . . . . . . . . . . . . . . . . . 71 Appendix C. JSON Pointer
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 71 Acknowledgements
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Contributors
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 72 Authors' Addresses
1. Introduction 1. Introduction
JSON [RFC8259] is a popular representation format for structured data JSON [RFC8259] is a popular representation format for structured data
values. JSONPath defines a string syntax for selecting and values. JSONPath defines a string syntax for selecting and
extracting JSON values from a JSON value. extracting JSON values from within a given JSON value.
JSONPath is not intended as a replacement for, but as a more powerful In relation to JSON Pointer [RFC6901], JSONPath is not intended as a
companion to, JSON Pointer [RFC6901]. See Appendix C. replacement but as a more powerful companion. See Appendix C.
1.1. Terminology 1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
The grammatical rules in this document are to be interpreted as ABNF, The grammatical rules in this document are to be interpreted as ABNF,
as described in [RFC5234]. ABNF terminal values in this document as described in [RFC5234]. ABNF terminal values in this document
define Unicode scalar values rather than their UTF-8 encoding. For define Unicode scalar values rather than their UTF-8 encoding. For
example, the Unicode PLACE OF INTEREST SIGN (U+2318) would be defined example, the Unicode PLACE OF INTEREST SIGN (U+2318) would be defined
in ABNF as %x2318. in ABNF as %x2318.
Functions are referred to using the function name followed by a pair Functions are referred to using the function name followed by a pair
of parentheses, as in fname(). of parentheses, as in fname().
The terminology of [RFC8259] applies except where clarified below. The terminology of [RFC8259] applies except where clarified below.
The terms "Primitive" and "Structured" are used to group different The terms "primitive" and "structured" are used to group different
kinds of values as in Section 1 of [RFC8259]; JSON Objects and Arrays kinds of values as in Section 1 of [RFC8259]. JSON objects and
are structured, all other values are primitive. Definitions for arrays are structured; all other values are primitive. Definitions
"Object", "Array", "Number", and "String" remain unchanged. for "object", "array", "number", and "string" remain unchanged.
Importantly "object" and "array" in particular do not take on a Importantly, "object" and "array" in particular do not take on a
generic meaning, such as they would in a general programming context. generic meaning, such as they would in a general programming context.
The terminology of [RFC9485] applies.
Additional terms used in this document are defined below. Additional terms used in this document are defined below.
Value: As per [RFC8259], a structure conforming to the generic data Value: As per [RFC8259], a data item conforming to the generic data
model of JSON, i.e., composed of constituents such as structured model of JSON, i.e., primitive data (numbers, text strings, and
values, namely JSON objects and arrays, and primitive data, namely the special values null, true, and false), or structured data
numbers and text strings as well as the special values null, true, (JSON objects and arrays). [RFC8259] focuses on the textual
and false. [RFC8259] focuses on the textual representation of representation of JSON values and does not fully define the value
JSON values and does not fully define the value abstraction abstraction assumed here.
assumed here.
Member: A name/value pair in an object. (A member is not itself a Member: A name/value pair in an object. (A member is not itself a
value.) value.)
Name: The name (a string) in a name/value pair constituting a Name: The name (a string) in a name/value pair constituting a
member. This is also used in [RFC8259], but that specification member. This is also used in [RFC8259], but that specification
does not formally define it. It is included here for does not formally define it. It is included here for
completeness. completeness.
Element: A value in a JSON array. Element: A value in a JSON array.
Index: An integer that identifies a specific element in an array. Index: An integer that identifies a specific element in an array.
Query: Short name for a JSONPath expression. Query: Short name for a JSONPath expression.
Query Argument: Short name for the value a JSONPath expression is Query Argument: Short name for the value a JSONPath expression is
applied to. (Also used for actual parameters of function- applied to.
expressions.)
Location: the position of a value within the query argument. This Location: The position of a value within the query argument. This
can be thought of as a sequence of names and indexes navigating to can be thought of as a sequence of names and indexes navigating to
the value through the objects and arrays in the query argument, the value through the objects and arrays in the query argument,
with the empty sequence indicating the query argument itself. A with the empty sequence indicating the query argument itself. A
location can be represented as a Normalized Path (defined below). location can be represented as a Normalized Path (defined below).
Node: The pair of a value along with its location within the query Node: The pair of a value along with its location within the query
argument. argument.
Root Node: The unique node whose value is the entire query argument. Root Node: The unique node whose value is the entire query argument.
Root Node Identifier: The expression $ which refers to the root node Root Node Identifier: The expression $, which refers to the root
of the query argument. node of the query argument.
Current Node Identifier: The expression @ which refers to the Current Node Identifier: The expression @, which refers to the
current node in the context of the evaluation of a filter current node in the context of the evaluation of a filter
expression (described later). expression (described later).
Children (of a node): If the node is an array, the nodes of its Children (of a node): If the node is an array, the nodes of its
elements. If the node is an object, the nodes of its member elements; if the node is an object, the nodes of its member
values. If the node is neither an array nor an object, it has no values. If the node is neither an array nor an object, it has no
children. children.
Descendants (of a node): The children of the node, together with the Descendants (of a node): The children of the node, together with the
children of its children, and so forth recursively. More children of its children, and so forth recursively. More
formally, the "descendants" relation between nodes is the formally, the "descendants" relation between nodes is the
transitive closure of the "children" relation. transitive closure of the "children" relation.
Depth (of a descendant node within a value): The number of ancestors Depth (of a descendant node within a value): The number of ancestors
of the node within the value. The root node of the value has of the node within the value. The root node of the value has
depth zero, the children of the root node have depth one, their depth zero, the children of the root node have depth one, their
children have depth two, and so forth. children have depth two, and so forth.
Nodelist: A list of nodes. While a nodelist can be represented in Nodelist: A list of nodes. While a nodelist can be represented in
JSON, e.g. as an array, this document does not require or assume JSON, e.g., as an array, this document does not require or assume
any particular representation. any particular representation.
Parameter: Formal parameter (of a function) that can take a function Parameter: Formal parameter (of a function) that can take a function
argument (an actual parameter) in a function-expression. argument (an actual parameter) in a function expression.
Normalized Path: A form of JSONPath expression that identifies a Normalized Path: A form of JSONPath expression that identifies a
node in a value by providing a query that results in exactly that node in a value by providing a query that results in exactly that
node. Each node in a query argument is identified by exactly one node. Each node in a query argument is identified by exactly one
Normalized Path (we say, the Normalized Path is "unique" for that Normalized Path (we say that the Normalized Path is "unique" for
node), and, to be a Normalized Path for a specific query argument, that node), and to be a Normalized Path for a specific query
the Normalized Path needs to identify exactly one node. Similar argument, the Normalized Path needs to identify exactly one node.
to, but syntactically different from, a JSON Pointer [RFC6901]. This is similar to, but syntactically different from, a JSON
Note: This definition is based on the syntactical definition in Pointer [RFC6901]. Note: This definition is based on the
Section 2.7; JSONPath expressions that identify a node in a value syntactical definition in Section 2.7; JSONPath expressions that
but do not conform to that syntax are not Normalized Paths. identify a node in a value but do not conform to that syntax are
not Normalized Paths.
Unicode Scalar Value: Any Unicode [UNICODE] code point except high- Unicode Scalar Value: Any Unicode [UNICODE] code point except high-
surrogate and low-surrogate code points. In other words, integers surrogate and low-surrogate code points (in other words, integers
in either of the inclusive base 16 ranges 0 to D7FF and E000 to in the inclusive base 16 ranges, either 0 to D7FF or E000 to
10FFFF. JSONPath queries are sequences of Unicode scalar values. 10FFFF). JSONPath queries are sequences of Unicode scalar values.
Segment: One of the constructs which select children ([<selectors>]) Segment: One of the constructs that selects children ([<selectors>])
or descendants (..[<selectors>]) of an input value. or descendants (..[<selectors>]) of an input value.
Selector: A single item within a segment that takes the input value Selector: A single item within a segment that takes the input value
and produces a nodelist consisting of child nodes of the input and produces a nodelist consisting of child nodes of the input
value. value.
Singular Query: A JSONPath expression built from segments that have Singular Query: A JSONPath expression built from segments that have
been syntactically restricted in a certain way (Section 2.3.5.1) been syntactically restricted in a certain way (Section 2.3.5.1)
so that, regardless of the input value, the expression produces a so that, regardless of the input value, the expression produces a
nodelist containing at most one node. Note: JSONPath expressions nodelist containing at most one node. Note: JSONPath expressions
that always produce a singular nodelist but do not conform to the that always produce a singular nodelist but do not conform to the
syntax in Section 2.3.5.1 are not Singular Queries. syntax in Section 2.3.5.1 are not singular queries.
1.1.1. JSON Values as Trees of Nodes 1.1.1. JSON Values as Trees of Nodes
This document models the query argument as a tree of JSON values, This document models the query argument as a tree of JSON values,
each with its own node. A node is either the root node or one of its each with its own node. A node is either the root node or one of its
descendants. descendants.
This document models the result of applying a query to the query This document models the result of applying a query to the query
argument as a nodelist (a list of nodes). argument as a nodelist (a list of nodes).
Nodes are the selectable parts of the query argument. The only parts Nodes are the selectable parts of the query argument. The only parts
of an object that can be selected by a query are the member values. of an object that can be selected by a query are the member values.
Member names and members (name/value pairs) cannot be selected. Member names and members (name/value pairs) cannot be selected.
Thus, member values have nodes, but members and member names do not. Thus, member values have nodes, but members and member names do not.
Similarly, member values are children of an object, but members and Similarly, member values are children of an object, but members and
member names are not. member names are not.
1.2. History 1.2. History
This document is based on Stefan Gössner's popular JSONPath proposal This document is based on Stefan Gössner's popular JSONPath proposal
dated 2007-02-21 [JSONPath-orig], builds on the experience from the (dated 2007-02-21) [JSONPath-orig], builds on the experience from the
widespread deployment of its implementations, and provides a widespread deployment of its implementations, and provides a
normative specification for it. normative specification for it.
Appendix B describes how JSONPath was inspired by XML's XPath Appendix B describes how JSONPath was inspired by XML's XPath
[XPath]. [XPath].
JSONPath was intended as a light-weight companion to JSON JSONPath was intended as a lightweight companion to JSON
implementations in programming languages such as PHP and JavaScript, implementations in programming languages such as PHP and JavaScript,
so instead of defining its own expression language, like XPath did, so instead of defining its own expression language, like XPath did,
JSONPath delegated parts of a query to the underlying runtime, e.g., JSONPath delegated parts of a query to the underlying runtime, e.g.,
JavaScript's eval() function. As JSONPath was implemented in more JavaScript's eval() function. As JSONPath was implemented in more
environments, JSONPath expressions became decreasingly portable. For environments, JSONPath expressions became decreasingly portable. For
example, regular expression processing was often delegated to a example, regular expression processing was often delegated to a
convenient regular expression engine. convenient regular expression engine.
This document aims to remove such implementation-specific This document aims to remove such implementation-specific
dependencies and serve as a common JSONPath specification that can be dependencies and serve as a common JSONPath specification that can be
skipping to change at page 8, line 12 skipping to change at line 328
document. Sections 4 and 8 of [RFC8259] identify specific situations document. Sections 4 and 8 of [RFC8259] identify specific situations
that may conform to the grammar for JSON texts but are not that may conform to the grammar for JSON texts but are not
interoperable uses of JSON, as they may cause unpredictable behavior. interoperable uses of JSON, as they may cause unpredictable behavior.
This document does not attempt to define predictable behavior for This document does not attempt to define predictable behavior for
JSONPath queries in these situations. JSONPath queries in these situations.
Specifically, the "Semantics" subsections of Sections 2.3.1, 2.3.2, Specifically, the "Semantics" subsections of Sections 2.3.1, 2.3.2,
2.3.5, and 2.5.2 describe behavior that becomes unpredictable when 2.3.5, and 2.5.2 describe behavior that becomes unpredictable when
the JSON value for one of the objects under consideration was the JSON value for one of the objects under consideration was
constructed out of JSON text that exhibits multiple members for a constructed out of JSON text that exhibits multiple members for a
single object that share the same member name ("duplicate names", see single object that share the same member name ("duplicate names"; see
Section 4 of [RFC8259]). Also, selecting a child by name Section 4 of [RFC8259]). Also, when selecting a child by name
(Section 2.3.1) and comparing strings (Section 2.3.5.2.2 in (Section 2.3.1) and comparing strings (Section 2.3.5.2.2), it is
Section 2.3.5) assume these strings are sequences of Unicode scalar assumed these strings are sequences of Unicode scalar values; the
values, becoming unpredictable if they are not (Section 8.2 of behavior becomes unpredictable if they are not (Section 8.2 of
[RFC8259]). [RFC8259]).
1.4. Overview of JSONPath Expressions 1.4. Overview of JSONPath Expressions
A JSONPath expression is applied to a JSON value, known as the query A JSONPath expression is applied to a JSON value, known as the query
argument. The output is a nodelist. argument. The output is a nodelist.
A JSONPath expression consists of an identifier followed by a series A JSONPath expression consists of an identifier followed by a series
of zero or more segments each of which contains one or more of zero or more segments, each of which contains one or more
selectors. selectors.
1.4.1. Identifiers 1.4.1. Identifiers
The root node identifier $ refers to the root node of the query The root node identifier $ refers to the root node of the query
argument, i.e., to the argument as a whole. argument, i.e., to the argument as a whole.
The current node identifier @ refers to the current node in the The current node identifier @ refers to the current node in the
context of the evaluation of a filter expression (Section 2.3.5). context of the evaluation of a filter expression (Section 2.3.5).
skipping to change at page 8, line 49 skipping to change at line 365
(..[<selectors>]) of an input value. (..[<selectors>]) of an input value.
Segments can use _bracket notation_, for example: Segments can use _bracket notation_, for example:
$['store']['book'][0]['title'] $['store']['book'][0]['title']
or the more compact _dot notation_, for example: or the more compact _dot notation_, for example:
$.store.book[0].title $.store.book[0].title
Bracket notation contains a comma separated list of one or more Bracket notation contains one or more (comma-separated) selectors of
selectors of any kind. Selectors are detailed in the next section. any kind. Selectors are detailed in the next section.
A JSONPath expression may use a combination of bracket and dot A JSONPath expression may use a combination of bracket and dot
notations. notations.
This document treats the bracket notations as canonical and defines This document treats the bracket notations as canonical and defines
the shorthand dot notation in terms of bracket notation. Examples the shorthand dot notation in terms of bracket notation. Examples
and descriptions use shorthands where convenient. and descriptions use shorthand where convenient.
1.4.3. Selectors 1.4.3. Selectors
A name selector, e.g. 'name', selects a named child of an object. A name selector, e.g., 'name', selects a named child of an object.
An index selector, e.g. 3, selects an indexed child of an array. An index selector, e.g., 3, selects an indexed child of an array.
A wildcard * (Section 2.3.2) in the expression [*] selects all In the expression [*], a wildcard * (Section 2.3.2) selects all
children of a node and in the expression ..[*] selects all children of a node, and in the expression ..[*], it selects all
descendants of a node. descendants of a node.
An array slice start:end:step (Section 2.3.4) selects a series of An array slice start:end:step (Section 2.3.4) selects a series of
elements from an array, giving a start position, an end position, and elements from an array, giving a start position, an end position, and
an optional step value that moves the position from the start to the an optional step value that moves the position from the start to the
end. end.
Filter expressions ?<logical-expr> select certain children of an A filter expression ?<logical-expr> selects certain children of an
object or array, as in: object or array, as in:
$.store.book[?@.price < 10].title $.store.book[?@.price < 10].title
1.4.4. Summary 1.4.4. Summary
Table 1 provides a brief overview of JSONPath syntax. Table 1 provides a brief overview of JSONPath syntax.
+=================+==============================================+ +==================+================================================+
| Syntax Element | Description | | Syntax Element | Description |
+=================+==============================================+ +==================+================================================+
| $ | root node identifier (Section 2.2) | | $ | root node identifier (Section 2.2) |
+-----------------+----------------------------------------------+ +------------------+------------------------------------------------+
| @ | current node identifier (Section 2.3.5) | | @ | current node identifier (Section 2.3.5) |
| | (valid only within filter selectors) | | | (valid only within filter selectors) |
+-----------------+----------------------------------------------+ +------------------+------------------------------------------------+
| [<selectors>] | child segment (Section 2.5.1) selects zero | | [<selectors>] | child segment (Section 2.5.1): selects |
| | or more children of a node; contains one or | | | zero or more children of a node |
| | more selectors, separated by commas | +------------------+------------------------------------------------+
+-----------------+----------------------------------------------+ | .name | shorthand for ['name'] |
| .name | shorthand for ['name'] | +------------------+------------------------------------------------+
+-----------------+----------------------------------------------+ | .* | shorthand for [*] |
| .* | shorthand for [*] | +------------------+------------------------------------------------+
+-----------------+----------------------------------------------+ | ..[<selectors>] | descendant segment (Section 2.5.2): |
| ..[<selectors>] | descendant segment (Section 2.5.2): selects | | | selects zero or more descendants of a node |
| | zero or more descendants of a node; contains | +------------------+------------------------------------------------+
| | one or more selectors, separated by commas | | ..name | shorthand for ..['name'] |
+-----------------+----------------------------------------------+ +------------------+------------------------------------------------+
| ..name | shorthand for ..['name'] | | ..* | shorthand for ..[*] |
+-----------------+----------------------------------------------+ +------------------+------------------------------------------------+
| ..* | shorthand for ..[*] | | 'name' | name selector (Section 2.3.1): selects a |
+-----------------+----------------------------------------------+ | | named child of an object |
| 'name' | name selector (Section 2.3.1): selects a | +------------------+------------------------------------------------+
| | named child of an object | | * | wildcard selector (Section 2.3.2): selects |
+-----------------+----------------------------------------------+ | | all children of a node |
| * | wildcard selector (Section 2.3.1): selects | +------------------+------------------------------------------------+
| | all children of a node | | 3 | index selector (Section 2.3.3): selects an |
+-----------------+----------------------------------------------+ | | indexed child of an array (from 0) |
| 3 | index selector (Section 2.3.3): selects an | +------------------+------------------------------------------------+
| | indexed child of an array (from 0) | | 0:100:5 | array slice selector (Section 2.3.4): |
+-----------------+----------------------------------------------+ | | start:end:step for arrays |
| 0:100:5 | array slice selector (Section 2.3.4): | +------------------+------------------------------------------------+
| | start:end:step for arrays | | ?<logical-expr> | filter selector (Section 2.3.5): selects |
+-----------------+----------------------------------------------+ | | particular children using a logical |
| ?<logical-expr> | filter selector (Section 2.3.5): selects | | | expression |
| | particular children using a logical | +------------------+------------------------------------------------+
| | expression | | length(@.foo) | function extension (Section 2.4): invokes |
+-----------------+----------------------------------------------+ | | a function in a filter expression |
| length(@.foo) | function extension (Section 2.4): invokes a | +------------------+------------------------------------------------+
| | function in a filter expression |
+-----------------+----------------------------------------------+
Table 1: Overview of JSONPath syntax Table 1: Overview of JSONPath Syntax
1.5. JSONPath Examples 1.5. JSONPath Examples
This section is informative. It provides examples of JSONPath This section is informative. It provides examples of JSONPath
expressions. expressions.
The examples are based on the simple JSON value shown in Figure 1, The examples are based on the simple JSON value shown in Figure 1,
representing a bookstore (that also has a bicycle). representing a bookstore (which also has a bicycle).
{ "store": { { "store": {
"book": [ "book": [
{ "category": "reference", { "category": "reference",
"author": "Nigel Rees", "author": "Nigel Rees",
"title": "Sayings of the Century", "title": "Sayings of the Century",
"price": 8.95 "price": 8.95
}, },
{ "category": "fiction", { "category": "fiction",
"author": "Evelyn Waugh", "author": "Evelyn Waugh",
skipping to change at page 11, line 45 skipping to change at line 483
"price": 22.99 "price": 22.99
} }
], ],
"bicycle": { "bicycle": {
"color": "red", "color": "red",
"price": 399 "price": 399
} }
} }
} }
Figure 1: Example JSON value Figure 1: Example JSON Value
Table 2 shows some JSONPath queries that might be applied to this Table 2 shows some JSONPath queries that might be applied to this
example and their intended results. example and their intended results.
+========================+=======================================+ +========================+=======================================+
| JSONPath | Intended result | | JSONPath | Intended Result |
+========================+=======================================+ +========================+=======================================+
| $.store.book[*].author | the authors of all books in the store | | $.store.book[*].author | the authors of all books in the store |
+------------------------+---------------------------------------+ +------------------------+---------------------------------------+
| $..author | all authors | | $..author | all authors |
+------------------------+---------------------------------------+ +------------------------+---------------------------------------+
| $.store.* | all things in store, which are some | | $.store.* | all things in the store, which are |
| | books and a red bicycle | | | some books and a red bicycle |
+------------------------+---------------------------------------+ +------------------------+---------------------------------------+
| $.store..price | the prices of everything in the store | | $.store..price | the prices of everything in the store |
+------------------------+---------------------------------------+ +------------------------+---------------------------------------+
| $..book[2] | the third book | | $..book[2] | the third book |
+------------------------+---------------------------------------+ +------------------------+---------------------------------------+
| $..book[2].author | the third book's author | | $..book[2].author | the third book's author |
+------------------------+---------------------------------------+ +------------------------+---------------------------------------+
| $..book[2].publisher | empty result: the third book does not | | $..book[2].publisher | empty result: the third book does not |
| | have a "publisher" member | | | have a "publisher" member |
+------------------------+---------------------------------------+ +------------------------+---------------------------------------+
skipping to change at page 12, line 37 skipping to change at line 520
| $..book[:2] | | | $..book[:2] | |
+------------------------+---------------------------------------+ +------------------------+---------------------------------------+
| $..book[?@.isbn] | all books with an ISBN number | | $..book[?@.isbn] | all books with an ISBN number |
+------------------------+---------------------------------------+ +------------------------+---------------------------------------+
| $..book[?@.price<10] | all books cheaper than 10 | | $..book[?@.price<10] | all books cheaper than 10 |
+------------------------+---------------------------------------+ +------------------------+---------------------------------------+
| $..* | all member values and array elements | | $..* | all member values and array elements |
| | contained in the input value | | | contained in the input value |
+------------------------+---------------------------------------+ +------------------------+---------------------------------------+
Table 2: Example JSONPath expressions and their intended Table 2: Example JSONPath Expressions and Their Intended
results when applied to the example JSON value Results When Applied to the Example JSON Value
2. JSONPath Syntax and Semantics 2. JSONPath Syntax and Semantics
2.1. Overview 2.1. Overview
A JSONPath _expression_ is a string which, when applied to a JSON A JSONPath _expression_ is a string that, when applied to a JSON
value, the _query argument_, selects zero or more nodes of the value (the _query argument_), selects zero or more nodes of the
argument and outputs these nodes as a nodelist. argument and outputs these nodes as a nodelist.
A query MUST be encoded using UTF-8. The grammar for queries given A query MUST be encoded using UTF-8. The grammar for queries given
in this document assumes that its UTF-8 form is first decoded into in this document assumes that its UTF-8 form is first decoded into
Unicode scalar values as described in [RFC3629]; implementation Unicode scalar values as described in [RFC3629]; implementation
approaches that lead to an equivalent result are possible. approaches that lead to an equivalent result are possible.
A string to be used as a JSONPath query needs to be _well-formed_ and A string to be used as a JSONPath query needs to be _well-formed_ and
_valid_. A string is a well-formed JSONPath query if it conforms to _valid_. A string is a well-formed JSONPath query if it conforms to
the ABNF syntax in this document. A well-formed JSONPath query is the ABNF syntax in this document. A well-formed JSONPath query is
valid if it also fulfills all semantic requirements posed by this valid if it also fulfills both semantic requirements posed by this
document, which are: document, which are as follows:
1. Integer numbers in the JSONPath query that are relevant to the 1. Integer numbers in the JSONPath query that are relevant to the
JSONPath processing (e.g., index values and steps) MUST be within JSONPath processing (e.g., index values and steps) MUST be within
the range of exact integer values defined in I-JSON (see the range of exact integer values defined in Internet JSON
Section 2.2 of [RFC7493]), namely within the interval [−(2^53)+1, (I-JSON) (see Section 2.2 of [RFC7493]), namely within the
(2^53)−1]. interval [-(2^53)+1, (2^53)-1].
2. Uses of function extensions MUST be _well-typed_, as described in 2. Uses of function extensions MUST be _well-typed_, as described in
Section 2.4. Section 2.4.3.
A JSONPath implementation MUST raise an error for any query which is A JSONPath implementation MUST raise an error for any query that is
not well-formed and valid. The well-formedness and the validity of not well-formed and valid. The well-formedness and the validity of
JSONPath queries are independent of the JSON value the query is JSONPath queries are independent of the JSON value the query is
applied to. No further errors relating to the well-formedness and applied to. No further errors relating to the well-formedness and
the validity of a JSONPath query can be raised during application of the validity of a JSONPath query can be raised during application of
the query to a value. This clearly separates well-formedness/ the query to a value. This clearly separates well-formedness/
validity errors in the query from mismatches that may actually stem validity errors in the query from mismatches that may actually stem
from flaws in the data. from flaws in the data.
Mismatches between the structure expected by a valid query and the Mismatches between the structure expected by a valid query and the
structure found in the data can lead to empty query results, which structure found in the data can lead to empty query results, which
may be unexpected and indicate bugs in either. JSONPath may be unexpected and indicate bugs in either. JSONPath
implementations might therefore want to provide diagnostics to the implementations might therefore want to provide diagnostics to the
application developer that aid in finding the cause of empty results. application developer that aid in finding the cause of empty results.
Obviously, an implementation can still fail when executing a JSONPath Obviously, an implementation can still fail when executing a JSONPath
query, e.g., because of resource depletion, but this is not modeled query, e.g., because of resource depletion, but this is not modeled
in this document. However, the implementation MUST NOT silently in this document. However, the implementation MUST NOT silently
malfunction. Specifically, if a valid JSONPath query is evaluated malfunction. Specifically, if a valid JSONPath query is evaluated
against a structured value whose size is too large to process the against a structured value whose size is too large to process the
query correctly (for instance requiring the processing of numbers query correctly (for instance, requiring the processing of numbers
that fall outside the range of exact values), the implementation MUST that fall outside the range of exact values), the implementation MUST
provide an indication of overflow. provide an indication of overflow.
(Readers familiar with the HTTP error model may be reminded of 400 (Readers familiar with the HTTP error model may be reminded of 400
type errors when pondering well-formedness and validity, while type errors when pondering well-formedness and validity, and they may
resource depletion and related errors are comparable to 500 type recognize resource depletion and related errors as comparable to 500
errors.) type errors.)
2.1.1. Syntax 2.1.1. Syntax
Syntactically, a JSONPath query consists of a root identifier ($), Syntactically, a JSONPath query consists of a root identifier ($),
which stands for a nodelist that contains the root node of the query which stands for a nodelist that contains the root node of the query
argument, followed by a possibly empty sequence of _segments_. argument, followed by a possibly empty sequence of _segments_.
jsonpath-query = root-identifier segments jsonpath-query = root-identifier segments
segments = *(S segment) segments = *(S segment)
skipping to change at page 14, line 27 skipping to change at line 602
%x0D ; Carriage return %x0D ; Carriage return
S = *B ; optional blank space S = *B ; optional blank space
The syntax and semantics of segments are defined in Section 2.5. The syntax and semantics of segments are defined in Section 2.5.
2.1.2. Semantics 2.1.2. Semantics
In this document, the semantics of a JSONPath query define the In this document, the semantics of a JSONPath query define the
required results and do not prescribe the internal workings of an required results and do not prescribe the internal workings of an
implementation. This document may describe semantics in a procedural implementation. This document may describe semantics in a procedural
step-by-step fashion, but such descriptions are normative only in the step-by-step fashion; however, such descriptions are normative only
sense that any implementation MUST produce an identical result, but in the sense that any implementation MUST produce an identical result
not in the sense that implementors are required to use the same but not in the sense that implementers are required to use the same
algorithms. algorithms.
The semantics are that a valid query is executed against a value, the The semantics are that a valid query is executed against a value (the
_query argument_, and produces a nodelist (i.e., a list of zero or _query argument_) and produces a nodelist (i.e., a list of zero or
more nodes of the value). more nodes of the value).
The query is a root identifier followed by a sequence of zero or more The query is a root identifier followed by a sequence of zero or more
segments, each of which is applied to the result of the previous root segments, each of which is applied to the result of the previous root
identifier or segment and provides input to the next segment. These identifier or segment and provides input to the next segment. These
results and inputs take the form of nodelists. results and inputs take the form of nodelists.
The nodelist resulting from the root identifier contains a single The nodelist resulting from the root identifier contains a single
node, the query argument. The nodelist resulting from the last node (the query argument). The nodelist resulting from the last
segment is presented as the result of the query. Depending on the segment is presented as the result of the query. Depending on the
specific API, it might be presented as an array of the JSON values at specific API, it might be presented as an array of the JSON values at
the nodes, an array of Normalized Paths referencing the nodes, or the nodes, an array of Normalized Paths referencing the nodes, or
both — or some other representation as desired by the implementation. both -- or some other representation as desired by the
Note: an empty nodelist is a valid query result. implementation. Note: An empty nodelist is a valid query result.
A segment operates on each of the nodes in its input nodelist in A segment operates on each of the nodes in its input nodelist in
turn, and the resultant nodelists are concatenated in the order of turn, and the resultant nodelists are concatenated in the order of
the input nodelist they were derived from to produce the result of the input nodelist they were derived from to produce the result of
the segment. A node may be selected more than once and appears that the segment. A node may be selected more than once and appears that
number of times in the nodelist. Duplicate nodes are not removed. number of times in the nodelist. Duplicate nodes are not removed.
A syntactically valid segment MUST NOT produce errors when executing A syntactically valid segment MUST NOT produce errors when executing
the query. This means that some operations that might be considered the query. This means that some operations that might be considered
erroneous, such as using an index lying outside the range of an erroneous, such as using an index lying outside the range of an
array, simply result in fewer nodes being selected. (Additional array, simply result in fewer nodes being selected. (Additional
discussion of this property can be found in the introduction to discussion of this property can be found in the introduction of
Section 2.1.) Section 2.1.)
As a consequence of this approach, if any of the segments produces an As a consequence of this approach, if any of the segments produces an
empty nodelist, then the whole query produces an empty nodelist. empty nodelist, then the whole query produces an empty nodelist.
If a query may produce a nodelist with more than one possible If the semantics of a query give an implementation a choice of
ordering, a particular implementation may also produce distinct producing multiple possible orderings, a particular implementation
orderings in successive runs of the query. may produce distinct orderings in successive runs of the query.
2.1.3. Example 2.1.3. Example
Consider this example. With the query argument Consider this example. With the query argument
{"a":[{"b":0},{"b":1},{"c":2}]}, the query $.a[*].b selects the {"a":[{"b":0},{"b":1},{"c":2}]}, the query $.a[*].b selects the
following list of nodes: 0, 1 (denoted here by their value). following list of nodes (denoted here by their values): 0, 1.
The query consists of $ followed by three segments: .a, [*], and .b. The query consists of $ followed by three segments: .a, [*], and .b.
Firstly, $ produces a nodelist consisting of just the query argument. First, $ produces a nodelist consisting of just the query argument.
Next, .a selects from any object input node and selects the node of Next, .a selects from any object input node and selects the node of
any member value of the input node corresponding to the member name any member value of the input node corresponding to the member name
"a". The result is again a list of one node: "a". The result is again a list containing a single node:
[{"b":0},{"b":1},{"c":2}]. [{"b":0},{"b":1},{"c":2}].
Next, [*] selects from any array input node all its elements (for an Next, [*] selects all the elements from the input array node. The
object input node, it would select all its member values, but not the result is a list of three nodes: {"b":0}, {"b":1}, and {"c":2}.
member names). The result is a list of three nodes: {"b":0},
{"b":1}, and {"c":2}.
Finally, .b selects from any object input node with a member name b Finally, .b selects from any object input node with a member name b
and selects the node of the member value of the input node and selects the node of the member value of the input node
corresponding to that name. The result is a list containing 0, 1. corresponding to that name. The result is a list containing 0, 1.
This is the concatenation of three lists, two of length one This is the concatenation of three lists: two of length one
containing 0, 1, respectively, and one of length zero. containing 0, 1, respectively, and one of length zero.
2.2. Root Identifier 2.2. Root Identifier
2.2.1. Syntax 2.2.1. Syntax
Every JSONPath query (except those inside filter expressions, see Every JSONPath query (except those inside filter expressions; see
Section 2.3.5) MUST begin with the root identifier $. Section 2.3.5) MUST begin with the root identifier $.
root-identifier = "$" root-identifier = "$"
2.2.2. Semantics 2.2.2. Semantics
The root identifier $ represents the root node of the query argument The root identifier $ represents the root node of the query argument
and produces a nodelist consisting of that root node. and produces a nodelist consisting of that root node.
2.2.3. Examples 2.2.3. Examples
| In this and the following examples in Sections 2.2 and 2.3 | Note: In this example and the following examples in Sections
| except for Table 11, we will present a JSON text to show the | 2.2 and 2.3, except for Table 11, we will present a JSON text
| JSON value used as the query argument to the queries in the | to show the JSON value used as the query argument to the
| examples, and then a table with the columns: | queries in the examples and then a table with the following
| columns:
| |
| * Query: an example query to be applied to the query | * Query: an example query to be applied to the query
| argument | argument
| |
| * Result: the query result as a list of JSON values that | * Result: the query result as a list of JSON values that
| were located in the query argument | were located in the query argument
| |
| * Result Path: the query result as a list of (normalized) | * Result Path: the query result as a list of (normalized)
| paths into the query argument, giving locations of the | paths into the query argument, giving locations of the
| JSON values in the previous column | JSON values in the previous column
skipping to change at page 16, line 47 skipping to change at line 714
{"k": "v"} {"k": "v"}
Queries: Queries:
+=======+============+=============+===========+ +=======+============+=============+===========+
| Query | Result | Result Path | Comment | | Query | Result | Result Path | Comment |
+=======+============+=============+===========+ +=======+============+=============+===========+
| $ | {"k": "v"} | $ | Root node | | $ | {"k": "v"} | $ | Root node |
+-------+------------+-------------+-----------+ +-------+------------+-------------+-----------+
Table 3: Root identifier examples Table 3: Root Identifier Example
2.3. Selectors 2.3. Selectors
Selectors appear only inside child segments (Section 2.5.1) and Selectors appear only inside child segments (Section 2.5.1) and
descendant segments (Section 2.5.2). descendant segments (Section 2.5.2).
A selector produces a nodelist consisting of zero or more children of A selector produces a nodelist consisting of zero or more children of
the input value. the input value.
There are various kinds of selectors which produce children of There are various kinds of selectors that produce children of
objects, children of arrays, or children of either objects or arrays. objects, children of arrays, or children of either objects or arrays.
selector = name-selector / selector = name-selector /
wildcard-selector / wildcard-selector /
slice-selector / slice-selector /
index-selector / index-selector /
filter-selector filter-selector
The syntax and semantics of each kind of selector are defined below. The syntax and semantics of each kind of selector are defined below.
2.3.1. Name Selector 2.3.1. Name Selector
2.3.1.1. Syntax 2.3.1.1. Syntax
skipping to change at page 18, line 20 skipping to change at line 759
double-quoted = unescaped / double-quoted = unescaped /
%x27 / ; ' %x27 / ; '
ESC %x22 / ; \" ESC %x22 / ; \"
ESC escapable ESC escapable
single-quoted = unescaped / single-quoted = unescaped /
%x22 / ; " %x22 / ; "
ESC %x27 / ; \' ESC %x27 / ; \'
ESC escapable ESC escapable
ESC = %x5C ; \ backslash ESC = %x5C ; \ backslash
unescaped = %x20-21 / ; see RFC 8259 unescaped = %x20-21 / ; see RFC 8259
; omit 0x22 " ; omit 0x22 "
%x23-26 / %x23-26 /
; omit 0x27 ' ; omit 0x27 '
%x28-5B / %x28-5B /
; omit 0x5C \ ; omit 0x5C \
%x5D-D7FF / ; skip surrogate code points %x5D-D7FF /
; skip surrogate code points
%xE000-10FFFF %xE000-10FFFF
escapable = %x62 / ; b BS backspace U+0008 escapable = %x62 / ; b BS backspace U+0008
%x66 / ; f FF form feed U+000C %x66 / ; f FF form feed U+000C
%x6E / ; n LF line feed U+000A %x6E / ; n LF line feed U+000A
%x72 / ; r CR carriage return U+000D %x72 / ; r CR carriage return U+000D
%x74 / ; t HT horizontal tab U+0009 %x74 / ; t HT horizontal tab U+0009
"/" / ; / slash (solidus) U+002F "/" / ; / slash (solidus) U+002F
"\" / ; \ backslash (reverse solidus) U+005C "\" / ; \ backslash (reverse solidus) U+005C
(%x75 hexchar) ; uXXXX U+XXXX (%x75 hexchar) ; uXXXX U+XXXX
hexchar = non-surrogate / hexchar = non-surrogate /
(high-surrogate "\" %x75 low-surrogate) (high-surrogate "\" %x75 low-surrogate)
non-surrogate = ((DIGIT / "A"/"B"/"C" / "E"/"F") 3HEXDIG) / non-surrogate = ((DIGIT / "A"/"B"/"C" / "E"/"F") 3HEXDIG) /
("D" %x30-37 2HEXDIG ) ("D" %x30-37 2HEXDIG )
high-surrogate = "D" ("8"/"9"/"A"/"B") 2HEXDIG high-surrogate = "D" ("8"/"9"/"A"/"B") 2HEXDIG
low-surrogate = "D" ("C"/"D"/"E"/"F") 2HEXDIG low-surrogate = "D" ("C"/"D"/"E"/"F") 2HEXDIG
HEXDIG = DIGIT / "A" / "B" / "C" / "D" / "E" / "F" HEXDIG = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
Notes: Notes:
* double-quoted strings follow the JSON string syntax (Section 7 of * Double-quoted strings follow the JSON string syntax (Section 7 of
[RFC8259]); single-quoted strings follow an analogous pattern [RFC8259]); single-quoted strings follow an analogous pattern. No
(Section 2.3.3.1). No attempt was made to improve on this syntax, attempt was made to improve on this syntax, so if it is desired to
so if it is desired to escape characters with scalar values above escape characters with scalar values above 0xFFFF, such as U+1F3BC
0xFFFF, such as U+1F914 ("🤔", THINKING FACE), they need to be ("🎼", MUSICAL SCORE), they need to be represented by a pair of
represented by a pair of surrogate escapes ("\uD83E\uDD14" in this surrogate escapes ("\uD83C\uDFBC" in this case).
case).
* Alphabetic characters in ABNF quoted strings are case-insensitive, * Alphabetic characters in quoted strings are case-insensitive in
so each of the hexadecimal digits within \u escapes (as specified ABNF, so each of the hexadecimal digits within \u escapes (as
in rules referenced by hexchar) can be either lower case or upper specified in rules referenced by hexchar) can be either lowercase
case, while the u in \u needs to be lower case (indicated as or uppercase, while the u in \u needs to be lowercase (indicated
%x75). as %x75).
2.3.1.2. Semantics 2.3.1.2. Semantics
A name-selector string MUST be converted to a member name M by A name-selector string MUST be converted to a member name M by
removing the surrounding quotes and replacing each escape sequence removing the surrounding quotes and replacing each escape sequence
with its equivalent Unicode character, as shown in Table 4: with its equivalent Unicode character, as shown in Table 4:
+=================+===================+=============================+ +=================+===================+=============================+
| Escape Sequence | Unicode Character | Description | | Escape Sequence | Unicode Character | Description |
+=================+===================+=============================+ +=================+===================+=============================+
skipping to change at page 20, line 6 skipping to change at line 839
| \\ | U+005C | backslash (reverse | | \\ | U+005C | backslash (reverse |
| | | solidus) | | | | solidus) |
+-----------------+-------------------+-----------------------------+ +-----------------+-------------------+-----------------------------+
| \uXXXX | see | hexadecimal escape | | \uXXXX | see | hexadecimal escape |
| | Section 2.3.1.1 | | | | Section 2.3.1.1 | |
+-----------------+-------------------+-----------------------------+ +-----------------+-------------------+-----------------------------+
Table 4: Escape Sequence Replacements Table 4: Escape Sequence Replacements
Applying the name-selector to an object node selects a member value Applying the name-selector to an object node selects a member value
whose name equals the member name M, or selects nothing if there is whose name equals the member name M or selects nothing if there is no
no such member value. Nothing is selected from a value that is not such member value. Nothing is selected from a value that is not an
an object. object.
Note: processing the name selector requires comparing the member name Note: Processing the name selector requires comparing the member name
string M with member name strings in the JSON to which the selector string M with member name strings in the JSON to which the selector
is being applied. Two strings MUST be considered equal if and only is being applied. Two strings MUST be considered equal if and only
if they are identical sequences of Unicode scalar values. In other if they are identical sequences of Unicode scalar values. In other
words, normalization operations MUST NOT be applied to either the words, normalization operations MUST NOT be applied to either the
member name string M from the JSONPath or to the member name strings member name string M from the JSONPath or the member name strings in
in the JSON prior to comparison. the JSON prior to comparison.
2.3.1.3. Examples 2.3.1.3. Examples
JSON: JSON:
{ {
"o": {"j j": {"k.k": 3}}, "o": {"j j": {"k.k": 3}},
"'": {"@": 2} "'": {"@": 2}
} }
Queries: Queries:
The examples in Table 5 show the name selector in use by child The examples in Table 5 show the name selector in use by child
segments: segments.
+===================+=========+======================+============+ +====================+=======+=======================+============+
| Query | Result | Result Paths | Comment | | Query |Result | Result Paths | Comment |
+===================+=========+======================+============+ +====================+=======+=======================+============+
| $.o['j j'] | {"k.k": | $['o']['j j'] | Named | | $.o['j j'] |{"k.k":| $['o']['j j'] | Named |
| | 3} | | value in | | |3} | | value in |
| | | | nested | | | | | a nested |
| | | | object | | | | | object |
+-------------------+---------+----------------------+------------+ +--------------------+-------+-----------------------+------------+
| $.o['j j']['k.k'] | 3 | $['o']['j j']['k.k'] | Nesting | | $.o['j j']['k.k'] |3 | $['o']['j j']['k.k'] | Nesting |
| | | | further | | | | | further |
| | | | down | | | | | down |
+-------------------+---------+----------------------+------------+ +--------------------+-------+-----------------------+------------+
| $.o["j j"]["k.k"] | 3 | $['o']['j j']['k.k'] | Different | | $.o["j j"]["k.k"] |3 | $['o']['j j']['k.k'] | Different |
| | | | delimiter | | | | | delimiter |
| | | | in query, | | | | | in the |
| | | | unchanged | | | | | query, |
| | | | normalized | | | | | unchanged |
| | | | path | | | | | Normalized |
+-------------------+---------+----------------------+------------+ | | | | Path |
| $["'"]["@"] | 2 | $['\'']['@'] | Unusual | +--------------------+-------+-----------------------+------------+
| | | | member | | $["'"]["@"] |2 | $['\'']['@'] | Unusual |
| | | | names | | | | | member |
+-------------------+---------+----------------------+------------+ | | | | names |
+--------------------+-------+-----------------------+------------+
Table 5: Name selector examples Table 5: Name Selector Examples
2.3.2. Wildcard Selector 2.3.2. Wildcard Selector
2.3.2.1. Syntax 2.3.2.1. Syntax
The wildcard selector consists of an asterisk. The wildcard selector consists of an asterisk.
wildcard-selector = "*" wildcard-selector = "*"
2.3.2.2. Semantics 2.3.2.2. Semantics
A wildcard selector selects the nodes of all children of an object or A wildcard selector selects the nodes of all children of an object or
array. The order in which the children of an object appear in the array. The order in which the children of an object appear in the
resultant nodelist is not stipulated, since JSON objects are resultant nodelist is not stipulated, since JSON objects are
unordered. Children of an array appear in array order in the unordered. Children of an array appear in array order in the
resultant nodelist. resultant nodelist.
Note that the children of an object are its member values, not its
member names.
The wildcard selector selects nothing from a primitive JSON value The wildcard selector selects nothing from a primitive JSON value
(that is, a number, a string, true, false, or null). (that is, a number, a string, true, false, or null).
2.3.2.3. Examples 2.3.2.3. Examples
JSON: JSON:
{ {
"o": {"j": 1, "k": 2}, "o": {"j": 1, "k": 2},
"a": [5, 3] "a": [5, 3]
} }
Queries: Queries:
The examples in Table 6 show the wildcard selector in use by a child The examples in Table 6 show the wildcard selector in use by a child
segment: segment.
+========+==========+=============+===================+ +========+==========+=============+===================+
| Query | Result | Result | Comment | | Query | Result | Result | Comment |
| | | Paths | | | | | Paths | |
+========+==========+=============+===================+ +========+==========+=============+===================+
| $[*] | {"j": 1, | $['o'] | Object values | | $[*] | {"j": 1, | $['o'] | Object values |
| | "k": 2} | $['a'] | | | | "k": 2} | $['a'] | |
| | [5, 3] | | | | | [5, 3] | | |
+--------+----------+-------------+-------------------+ +--------+----------+-------------+-------------------+
| $.o[*] | 1 | $['o']['j'] | Object values | | $.o[*] | 1 | $['o']['j'] | Object values |
skipping to change at page 22, line 42 skipping to change at line 951
+--------+----------+-------------+-------------------+ +--------+----------+-------------+-------------------+
| $.o[*, | 1 | $['o']['j'] | Non-deterministic | | $.o[*, | 1 | $['o']['j'] | Non-deterministic |
| *] | 2 | $['o']['k'] | ordering | | *] | 2 | $['o']['k'] | ordering |
| | 2 | $['o']['k'] | | | | 2 | $['o']['k'] | |
| | 1 | $['o']['j'] | | | | 1 | $['o']['j'] | |
+--------+----------+-------------+-------------------+ +--------+----------+-------------+-------------------+
| $.a[*] | 5 | $['a'][0] | Array members | | $.a[*] | 5 | $['a'][0] | Array members |
| | 3 | $['a'][1] | | | | 3 | $['a'][1] | |
+--------+----------+-------------+-------------------+ +--------+----------+-------------+-------------------+
Table 6: Wildcard selector examples Table 6: Wildcard Selector Examples
The example above with the query $.o[*, *] shows that the wildcard The example above with the query $.o[*, *] shows that the wildcard
selector may produce nodelists in distinct orders each time it selector may produce nodelists in distinct orders each time it
appears in the child segment, when it is applied to an object node appears in the child segment when it is applied to an object node
with two or more members (but not when it is applied to object nodes with two or more members (but not when it is applied to object nodes
with fewer than two members or to array nodes). with fewer than two members or to array nodes).
2.3.3. Index Selector 2.3.3. Index Selector
2.3.3.1. Syntax 2.3.3.1. Syntax
An index selector <index> matches at most one array element value. An index selector <index> matches at most one array element value.
index-selector = int ; decimal integer index-selector = int ; decimal integer
int = "0" / int = "0" /
(["-"] DIGIT1 *DIGIT) ; - optional (["-"] DIGIT1 *DIGIT) ; - optional
DIGIT1 = %x31-39 ; 1-9 non-zero digit DIGIT1 = %x31-39 ; 1-9 non-zero digit
Applying the numerical index-selector selects the corresponding Applying the numerical index-selector selects the corresponding
element. JSONPath allows it to be negative (see Section 2.3.3.2). element. JSONPath allows it to be negative (see Section 2.3.3.2).
To be valid, the index selector value MUST be in the I-JSON range of To be valid, the index selector value MUST be in the I-JSON range of
exact values, see Section 2.1. exact values (see Section 2.1).
Notes: Notes:
* An index-selector is an integer (in base 10, as in JSON numbers). * An index-selector is an integer (in base 10, as in JSON numbers).
* As in JSON numbers, the syntax does not allow octal-like integers * As in JSON numbers, the syntax does not allow octal-like integers
with leading zeros such as 01 or -01. with leading zeros, such as 01 or -01.
2.3.3.2. Semantics 2.3.3.2. Semantics
A non-negative index-selector applied to an array selects an array A non-negative index-selector applied to an array selects an array
element using a zero-based index. For example, the selector 0 element using a zero-based index. For example, the selector 0
selects the first and the selector 4 selects the fifth element of a selects the first, and the selector 4 selects the fifth element of a
sufficiently long array. Nothing is selected, and it is not an sufficiently long array. Nothing is selected, and it is not an
error, if the index lies outside the range of the array. Nothing is error, if the index lies outside the range of the array. Nothing is
selected from a value that is not an array. selected from a value that is not an array.
A negative index-selector counts from the array end backwards, A negative index-selector counts from the array end backwards,
obtaining an equivalent non-negative index-selector by summing the obtaining an equivalent non-negative index-selector by adding the
length of the array with the negative index. For example, the length of the array to the negative index. For example, the selector
selector -1 selects the last and the selector -2 selects the -1 selects the last, and the selector -2 selects the penultimate
penultimate element of an array with at least two elements. As with element of an array with at least two elements. As with non-negative
non-negative indexes, it is not an error if such an element does not indexes, it is not an error if such an element does not exist; this
exist; this simply means that no element is selected. simply means that no element is selected.
2.3.3.3. Examples 2.3.3.3. Examples
JSON: JSON:
["a","b"] ["a","b"]
Queries: Queries:
The examples in Table 7 show the index selector in use by a child The examples in Table 7 show the index selector in use by a child
segment. segment.
+=======+========+==============+================================+ +=======+========+==============+================================+
| Query | Result | Result Paths | Comment | | Query | Result | Result Paths | Comment |
+=======+========+==============+================================+ +=======+========+==============+================================+
| $[1] | "b" | $[1] | Element of array | | $[1] | "b" | $[1] | Element of array |
+-------+--------+--------------+--------------------------------+ +-------+--------+--------------+--------------------------------+
| $[-2] | "a" | $[0] | Element of array, from the end | | $[-2] | "a" | $[0] | Element of array, from the end |
+-------+--------+--------------+--------------------------------+ +-------+--------+--------------+--------------------------------+
Table 7: Index selector examples Table 7: Index Selector Examples
2.3.4. Array Slice selector 2.3.4. Array Slice Selector
2.3.4.1. Syntax 2.3.4.1. Syntax
The array slice selector has the form <start>:<end>:<step>. It The array slice selector has the form <start>:<end>:<step>. It
matches elements from arrays starting at index <start>, ending at — matches elements from arrays starting at index <start> and ending at
but not including — <end>, while incrementing by step with a default (but not including) <end>, while incrementing by step with a default
of 1. of 1.
slice-selector = [start S] ":" S [end S] [":" [S step ]] slice-selector = [start S] ":" S [end S] [":" [S step ]]
start = int ; included in selection start = int ; included in selection
end = int ; not included in selection end = int ; not included in selection
step = int ; default: 1 step = int ; default: 1
The slice selector consists of three optional decimal integers The slice selector consists of three optional decimal integers
separated by colons. The second colon can be omitted when the third separated by colons. The second colon can be omitted when the third
integer is. integer is omitted.
To be valid, the integers provided MUST be in the I-JSON range of To be valid, the integers provided MUST be in the I-JSON range of
exact values, see Section 2.1. exact values (see Section 2.1).
2.3.4.2. Semantics 2.3.4.2. Semantics
The slice selector was inspired by the slice operator of ECMAScript 4 The slice selector was inspired by the slice operator that was
(ES4), which was deprecated in 2014, and that of Python. proposed for ECMAScript 4 (ES4), which was never released, and that
of Python.
2.3.4.2.1. Informal Introduction 2.3.4.2.1. Informal Introduction
This section is informative. This section is informative.
Array slicing is inspired by the behavior of the Array slicing is inspired by the behavior of the
Array.prototype.slice method of the JavaScript language as defined by Array.prototype.slice method of the JavaScript language, as defined
the ECMA-262 standard [ECMA-262], with the addition of the step by the ECMA-262 standard [ECMA-262], with the addition of the step
parameter, which is inspired by the Python slice expression. parameter, which is inspired by the Python slice expression.
The array slice expression start:end:step selects elements at indices The array slice expression start:end:step selects elements at indices
starting at start, incrementing by step, and ending with end (which starting at start, incrementing by step, and ending with end (which
is itself excluded). So, for example, the expression 1:3 (where step is itself excluded). So, for example, the expression 1:3 (where step
defaults to 1) selects elements with indices 1 and 2 (in that order) defaults to 1) selects elements with indices 1 and 2 (in that order),
whereas 1:5:2 selects elements with indices 1 and 3. whereas 1:5:2 selects elements with indices 1 and 3.
When step is negative, elements are selected in reverse order. Thus, When step is negative, elements are selected in reverse order. Thus,
for example, 5:1:-2 selects elements with indices 5 and 3, in that for example, 5:1:-2 selects elements with indices 5 and 3 (in that
order and ::-1 selects all the elements of an array in reverse order. order), and ::-1 selects all the elements of an array in reverse
order.
When step is 0, no elements are selected. (This is the one case that When step is 0, no elements are selected. (This is the one case that
differs from the behavior of Python, which raises an error in this differs from the behavior of Python, which raises an error in this
case.) case.)
The following section specifies the behavior fully, without depending The following section specifies the behavior fully, without depending
on JavaScript or Python behavior. on JavaScript or Python behavior.
2.3.4.2.2. Normative Semantics 2.3.4.2.2. Normative Semantics
A slice expression selects a subset of the elements of the input A slice expression selects a subset of the elements of the input
array, in the same order as the array or the reverse order, depending array in the same order as the array or the reverse order, depending
on the sign of the step parameter. It selects no nodes from a node on the sign of the step parameter. It selects no nodes from a node
that is not an array. that is not an array.
A slice is defined by the two slice parameters, start and end, and an A slice is defined by the two slice parameters, start and end, and an
iteration delta, step. Each of these parameters is optional. In the iteration delta, step. Each of these parameters is optional. In the
rest of this section, len denotes the length of the input array. rest of this section, len denotes the length of the input array.
The default value for step is 1. The default values for start and The default value for step is 1. The default values for start and
end depend on the sign of step, as shown in Table 8: end depend on the sign of step, as shown in Table 8.
+===========+=========+==========+ +===========+=========+==========+
| Condition | start | end | | Condition | start | end |
+===========+=========+==========+ +===========+=========+==========+
| step >= 0 | 0 | len | | step >= 0 | 0 | len |
+-----------+---------+----------+ +-----------+---------+----------+
| step < 0 | len - 1 | -len - 1 | | step < 0 | len - 1 | -len - 1 |
+-----------+---------+----------+ +-----------+---------+----------+
Table 8: Default array slice Table 8: Default Array Slice
start and end values start and end Values
Slice expression parameters start and end are not directly usable as Slice expression parameters start and end are not directly usable as
slice bounds and must first be normalized. Normalization for this slice bounds and must first be normalized. Normalization for this
purpose is defined as: purpose is defined as:
FUNCTION Normalize(i, len): FUNCTION Normalize(i, len):
IF i >= 0 THEN IF i >= 0 THEN
RETURN i RETURN i
ELSE ELSE
RETURN len + i RETURN len + i
skipping to change at page 27, line 23 skipping to change at line 1159
ELSE if step < 0 THEN ELSE if step < 0 THEN
i = upper i = upper
WHILE lower < i: WHILE lower < i:
SELECT a(i) SELECT a(i)
i = i + step i = i + step
END WHILE END WHILE
END IF END IF
When step = 0, no elements are selected and the result array is When step = 0, no elements are selected, and the result array is
empty. empty.
2.3.4.3. Examples 2.3.4.3. Examples
JSON: JSON:
["a", "b", "c", "d", "e", "f", "g"] ["a", "b", "c", "d", "e", "f", "g"]
Queries: Queries:
The examples in Table 9 show the array slice selector in use by a The examples in Table 9 show the array slice selector in use by a
child segment: child segment.
+===========+========+========+==========+ +===========+========+========+==========+
| Query | Result | Result | Comment | | Query | Result | Result | Comment |
| | | Paths | | | | | Paths | |
+===========+========+========+==========+ +===========+========+========+==========+
| $[1:3] | "b" | $[1] | Slice | | $[1:3] | "b" | $[1] | Slice |
| | "c" | $[2] | with | | | "c" | $[2] | with |
| | | | default | | | | | default |
| | | | step | | | | | step |
+-----------+--------+--------+----------+ +-----------+--------+--------+----------+
skipping to change at page 28, line 37 skipping to change at line 1205
+-----------+--------+--------+----------+ +-----------+--------+--------+----------+
| $[::-1] | "g" | $[6] | Slice in | | $[::-1] | "g" | $[6] | Slice in |
| | "f" | $[5] | reverse | | | "f" | $[5] | reverse |
| | "e" | $[4] | order | | | "e" | $[4] | order |
| | "d" | $[3] | | | | "d" | $[3] | |
| | "c" | $[2] | | | | "c" | $[2] | |
| | "b" | $[1] | | | | "b" | $[1] | |
| | "a" | $[0] | | | | "a" | $[0] | |
+-----------+--------+--------+----------+ +-----------+--------+--------+----------+
Table 9: Array slice selector examples Table 9: Array Slice Selector Examples
2.3.5. Filter selector 2.3.5. Filter Selector
Filter selectors are used to iterate over the elements or members of Filter selectors are used to iterate over the elements or members of
structured values, i.e., JSON arrays and objects. The structured structured values, i.e., JSON arrays and objects. The structured
values are identified in the nodelist offered by the child or values are identified in the nodelist offered by the child or
descendant segment using the filter selector. descendant segment using the filter selector.
For each iteration (element/member), a logical expression, the For each iteration (element/member), a logical expression (the
_filter expression_, is evaluated which decides whether the node of _filter expression_) is evaluated, which decides whether the node of
the element/member is selected. (While a logical expression the element/member is selected. (While a logical expression
evaluates to what mathematically is a Boolean value, this evaluates to what mathematically is a Boolean value, this
specification uses the term _logical_ to maintain a distinction from specification uses the term _logical_ to maintain a distinction from
the Boolean values that JSON can represent.) the Boolean values that JSON can represent.)
During the iteration process, the filter expression receives the node During the iteration process, the filter expression receives the node
of each array element or object member value of the structured value of each array element or object member value of the structured value
being filtered; this element or member value is then known as the being filtered; this element or member value is then known as the
_current node_. _current node_.
The current node can be used as the start of one or more JSONPath The current node can be used as the start of one or more JSONPath
queries in subexpressions of the filter expression, notated via the queries in subexpressions of the filter expression, notated via the
current-node-identifier @. Each JSONPath query can be used either for current-node-identifier @. Each JSONPath query can be used either for
testing existence of a result of the query, for obtaining a specific testing existence of a result of the query, for obtaining a specific
JSON value resulting from that query that can then be used in a JSON value resulting from that query that can then be used in a
comparison, or as a _function argument_. comparison, or as a _function argument_.
Filter selectors may use function extensions, which are covered in Filter selectors may use function extensions, which are covered in
Section 2.4. Within the logical expression for a filter selector, Section 2.4. Within the logical expression for a filter selector,
function expressions can be used to operate on nodelists and values. function expressions can be used to operate on nodelists and values.
The set of available functions is extensible, with a number of The set of available functions is extensible, with a number of
functions predefined, see Section 2.4, and the ability to register functions predefined (see Section 2.4) and the ability to register
further functions provided by the Function Extensions sub-registry further functions provided by the "Function Extensions" subregistry
(Section 3.2). When a function is defined, it is given a unique (Section 3.2). When a function is defined, it is given a unique
name, and its return value and each of its parameters is given a name, and its return value and each of its parameters are given a
_declared type_. The type system is limited in scope; its purpose is _declared type_. The type system is limited in scope; its purpose is
to express restrictions that, without functions, are implicit in the to express restrictions that, without functions, are implicit in the
grammar of filter expressions. The type system also guides grammar of filter expressions. The type system also guides
conversions (Section 2.4.2) that mimic the way different kinds of conversions (Section 2.4.2) that mimic the way different kinds of
expressions are handled in the grammar when function expressions are expressions are handled in the grammar when function expressions are
not in use. not in use.
2.3.5.1. Syntax 2.3.5.1. Syntax
The filter selector has the form ?<logical-expr>. The filter selector has the form ?<logical-expr>.
filter-selector = "?" S logical-expr filter-selector = "?" S logical-expr
As the filter expression is composed of side-effect free As the filter expression is composed of constituents free of side
constituents, the order of evaluation does not need to be (and is effects, the order of evaluation does not need to be (and is not)
not) defined. Similarly, for conjunction (&&) and disjunction (||) defined. Similarly, for conjunction (&&) and disjunction (||)
(defined later), both a short-circuiting and a fully evaluating (defined later), both a short-circuiting and a fully evaluating
implementation will lead to the same result; both implementation implementation will lead to the same result; both implementation
strategies are therefore valid. strategies are therefore valid.
The current node is accessible via the current node identifier @. The current node is accessible via the current node identifier @.
This identifier addresses the current node of the filter-selector This identifier addresses the current node of the filter-selector
that is directly enclosing the identifier. Note: within nested that is directly enclosing the identifier. Note: Within nested
filter-selectors, there is no syntax to address the current node of filter-selectors, there is no syntax to address the current node of
any other than the directly enclosing filter-selector (i.e., of any other than the directly enclosing filter-selector (i.e., of
filter-selectors enclosing the filter-selector that is directly filter-selectors enclosing the filter-selector that is directly
enclosing the identifier). enclosing the identifier).
Logical expressions offer the usual Boolean operators (|| for OR, && Logical expressions offer the usual Boolean operators (|| for OR, &&
for AND, and ! for NOT). They have the normal semantics of Boolean for AND, and ! for NOT). They have the normal semantics of Boolean
algebra and obey its laws (see, for example, [BOOLEAN-LAWS]). algebra and obey its laws (for example, see [BOOLEAN-LAWS]).
Parentheses MAY be used within logical-expr for grouping. Parentheses MAY be used within logical-expr for grouping.
It is not required that logical-expr consist of a parenthesized It is not required that logical-expr consist of a parenthesized
expression (which was required in [JSONPath-orig]), although it can expression (which was required in [JSONPath-orig]), although it can
be, and the semantics are the same as without the parentheses. be, and the semantics are the same as without the parentheses.
logical-expr = logical-or-expr logical-expr = logical-or-expr
logical-or-expr = logical-and-expr *(S "||" S logical-and-expr) logical-or-expr = logical-and-expr *(S "||" S logical-and-expr)
; disjunction ; disjunction
; binds less tightly than conjunction ; binds less tightly than conjunction
skipping to change at page 30, line 40 skipping to change at line 1304
A test expression either tests the existence of a node designated by A test expression either tests the existence of a node designated by
an embedded query (see Section 2.3.5.2.1) or tests the result of a an embedded query (see Section 2.3.5.2.1) or tests the result of a
function expression (see Section 2.4). In the latter case, if the function expression (see Section 2.4). In the latter case, if the
function's declared result type is LogicalType (see Section 2.4.1), function's declared result type is LogicalType (see Section 2.4.1),
it tests whether the result is LogicalTrue; if the function's it tests whether the result is LogicalTrue; if the function's
declared result type is NodesType, it tests whether the result is declared result type is NodesType, it tests whether the result is
non-empty. If the function's declared result type is ValueType, its non-empty. If the function's declared result type is ValueType, its
use in a test expression is not well-typed (see Section 2.4.3). use in a test expression is not well-typed (see Section 2.4.3).
test-expr = [logical-not-op S] test-expr = [logical-not-op S]
(filter-query / ; existence/non-existence (filter-query / ; existence/non-existence
function-expr) ; LogicalType or NodesType function-expr) ; LogicalType or NodesType
filter-query = rel-query / jsonpath-query filter-query = rel-query / jsonpath-query
rel-query = current-node-identifier segments rel-query = current-node-identifier segments
current-node-identifier = "@" current-node-identifier = "@"
Comparison expressions are available for comparisons between Comparison expressions are available for comparisons between
primitive values (that is, numbers, strings, true, false, and null). primitive values (that is, numbers, strings, true, false, and null).
These can be obtained via literal values; singular queries, each of These can be obtained via literal values; singular queries, each of
which selects at most one node the value of which is then used; or which selects at most one node, the value of which is then used; or
function expressions (see Section 2.4) of type ValueType. function expressions (see Section 2.4) of type ValueType.
comparison-expr = comparable S comparison-op S comparable comparison-expr = comparable S comparison-op S comparable
literal = number / string-literal / literal = number / string-literal /
true / false / null true / false / null
comparable = literal / comparable = literal /
singular-query / ; singular query value singular-query / ; singular query value
function-expr ; ValueType function-expr ; ValueType
comparison-op = "==" / "!=" / comparison-op = "==" / "!=" /
"<=" / ">=" / "<=" / ">=" /
skipping to change at page 31, line 26 skipping to change at line 1337
rel-singular-query = current-node-identifier singular-query-segments rel-singular-query = current-node-identifier singular-query-segments
abs-singular-query = root-identifier singular-query-segments abs-singular-query = root-identifier singular-query-segments
singular-query-segments = *(S (name-segment / index-segment)) singular-query-segments = *(S (name-segment / index-segment))
name-segment = ("[" name-selector "]") / name-segment = ("[" name-selector "]") /
("." member-name-shorthand) ("." member-name-shorthand)
index-segment = "[" index-selector "]" index-segment = "[" index-selector "]"
Literals can be notated in the way that is usual for JSON (with the Literals can be notated in the way that is usual for JSON (with the
extension that strings can use single-quote delimiters). extension that strings can use single-quote delimiters).
Note: Alphabetic characters in ABNF quoted strings are case- Note: Alphabetic characters in quoted strings are case-insensitive in
insensitive, so within a floating point number the ABNF expression ABNF, so within a floating point number, the ABNF expression "e" can
"e" can be either the character 'e' or 'E'. be either the character 'e' or 'E'.
true, false, and null are lower-case only (case-sensitive). true, false, and null are lowercase only (case-sensitive).
number = (int / "-0") [ frac ] [ exp ] ; decimal number number = (int / "-0") [ frac ] [ exp ] ; decimal number
frac = "." 1*DIGIT ; decimal fraction frac = "." 1*DIGIT ; decimal fraction
exp = "e" [ "-" / "+" ] 1*DIGIT ; decimal exponent exp = "e" [ "-" / "+" ] 1*DIGIT ; decimal exponent
true = %x74.72.75.65 ; true true = %x74.72.75.65 ; true
false = %x66.61.6c.73.65 ; false false = %x66.61.6c.73.65 ; false
null = %x6e.75.6c.6c ; null null = %x6e.75.6c.6c ; null
Table 10 lists filter expression operators in order of precedence Table 10 lists filter expression operators in order of precedence
from highest (binds most tightly) to lowest (binds least tightly). from highest (binds most tightly) to lowest (binds least tightly).
skipping to change at page 32, line 21 skipping to change at line 1369
| 4 | Logical NOT | ! | | 4 | Logical NOT | ! |
+------------+----------------------+-------------+ +------------+----------------------+-------------+
| 3 | Relations | == != | | 3 | Relations | == != |
| | | < <= > >= | | | | < <= > >= |
+------------+----------------------+-------------+ +------------+----------------------+-------------+
| 2 | Logical AND | && | | 2 | Logical AND | && |
+------------+----------------------+-------------+ +------------+----------------------+-------------+
| 1 | Logical OR | || | | 1 | Logical OR | || |
+------------+----------------------+-------------+ +------------+----------------------+-------------+
Table 10: Filter expression operator precedence Table 10: Filter Expression Operator Precedence
2.3.5.2. Semantics 2.3.5.2. Semantics
The filter selector works with arrays and objects exclusively. Its The filter selector works with arrays and objects exclusively. Its
result is a list of _zero_, _one_, _multiple_ or _all_ of their array result is a list of (_zero_, _one_, _multiple_, or _all_) their array
elements or member values, respectively. Applied to a primitive elements or member values, respectively. Applied to a primitive
value, it selects nothing (and therefore does not contribute to the value, it selects nothing (and therefore does not contribute to the
result of the filter selector). result of the filter selector).
In the resultant nodelist, children of an array are ordered by their In the resultant nodelist, children of an array are ordered by their
position in the array. The order in which the children of an object position in the array. The order in which the children of an object
(as opposed to an array) appear in the resultant nodelist is not (as opposed to an array) appear in the resultant nodelist is not
stipulated, since JSON objects are unordered. stipulated, since JSON objects are unordered.
2.3.5.2.1. Existence Tests 2.3.5.2.1. Existence Tests
A query by itself in a logical context is an existence test which A query by itself in a logical context is an existence test that
yields true if the query selects at least one node and yields false yields true if the query selects at least one node and yields false
if the query does not select any nodes. if the query does not select any nodes.
Existence tests differ from comparisons in that: Existence tests differ from comparisons in that:
* they work with arbitrary relative or absolute queries (not just * They work with arbitrary relative or absolute queries (not just
singular queries). singular queries).
* they work with queries that select structured values. * They work with queries that select structured values.
To examine the value of a node selected by a query, an explicit To examine the value of a node selected by a query, an explicit
comparison is necessary. For example, to test whether the node comparison is necessary. For example, to test whether the node
selected by the query @.foo has the value null, use @.foo == null selected by the query @.foo has the value null, use @.foo == null
(see Section 2.6) rather than the negated existence test !@.foo (see Section 2.6) rather than the negated existence test !@.foo
(which yields false if @.foo selects a node, regardless of the node's (which yields false if @.foo selects a node, regardless of the node's
value). Similarly, @.foo == false yields true only if @.foo selects value). Similarly, @.foo == false yields true only if @.foo selects
a node and the value of that node is false. a node and the value of that node is false.
2.3.5.2.2. Comparisons 2.3.5.2.2. Comparisons
The comparison operators == and < are defined first and then these The comparison operators == and < are defined first, and then these
are used to define !=, <=, >, and >=. are used to define !=, <=, >, and >=.
When either side of a comparison results in an empty nodelist or the When either side of a comparison results in an empty nodelist or the
special result Nothing (see Section 2.4.1): special result Nothing (see Section 2.4.1):
* a comparison using the operator == yields true if and only the * A comparison using the operator == yields true if and only the
other side also results in an empty nodelist or the special result other side also results in an empty nodelist or the special result
Nothing. Nothing.
* a comparison using the operator < yields false. * A comparison using the operator < yields false.
When any query or function expression on either side of a comparison When any query or function expression on either side of a comparison
results in a nodelist consisting of a single node, that side is results in a nodelist consisting of a single node, that side is
replaced by the value of its node and then: replaced by the value of its node and then:
* a comparison using the operator == yields true if and only if the * A comparison using the operator == yields true if and only if the
comparison is between: comparison is between:
- numbers expected to interoperate as per Section 2.2 of I-JSON - numbers expected to interoperate, as per Section 2.2 of I-JSON
[RFC7493] that compare equal using normal mathematical [RFC7493], that compare equal using normal mathematical
equality, equality,
- numbers at least one of which is not expected to interoperate - numbers, at least one of which is not expected to interoperate
as per I-JSON, where the numbers compare equal using an as per I-JSON, where the numbers compare equal using an
implementation specific equality, implementation-specific equality,
- equal primitive values which are not numbers, - equal primitive values that are not numbers,
- equal arrays, that is arrays of the same length where each - equal arrays, that is, arrays of the same length where each
element of the first array is equal to the corresponding element of the first array is equal to the corresponding
element of the second array, or element of the second array, or
- equal objects with no duplicate names, that is where: - equal objects with no duplicate names, that is, where:
o both objects have the same collection of names (with no o both objects have the same collection of names (with no
duplicates), and duplicates) and
o for each of those names, the values associated with the name o for each of those names, the values associated with the name
by the objects are equal. by the objects are equal.
* a comparison using the operator < yields true if and only if the * A comparison using the operator < yields true if and only if the
comparison is between values which are both numbers or both comparison is between values that are both numbers or both strings
strings and which satisfy the comparison: and that satisfy the comparison:
- numbers expected to interoperate as per Section 2.2 of I-JSON - numbers expected to interoperate, as per Section 2.2 of I-JSON
[RFC7493] MUST compare using the normal mathematical ordering; [RFC7493], MUST compare using the normal mathematical ordering;
numbers not expected to interoperate as per I-JSON MAY compare numbers not expected to interoperate, as per I-JSON, MAY
using an implementation specific ordering compare using an implementation-specific ordering,
- the empty string compares less than any non-empty string - the empty string compares less than any non-empty string, and
- a non-empty string compares less than another non-empty string - a non-empty string compares less than another non-empty string
if and only if the first string starts with a lower Unicode if and only if the first string starts with a lower Unicode
scalar value than the second string or if both strings start scalar value than the second string or if both strings start
with the same Unicode scalar value and the remainder of the with the same Unicode scalar value and the remainder of the
first string compares less than the remainder of the second first string compares less than the remainder of the second
string. string.
!=, <=, >, and >= are defined in terms of the other comparison !=, <=, >, and >= are defined in terms of the other comparison
operators. For any a and b: operators. For any a and b:
skipping to change at page 35, line 5 skipping to change at line 1494
JSON: JSON:
{ {
"obj": {"x": "y"}, "obj": {"x": "y"},
"arr": [2, 3] "arr": [2, 3]
} }
Comparisons: Comparisons:
+========================+========+============================+ +========================+========+========================+
| Comparison | Result | Comment | | Comparison | Result | Comment |
+========================+========+============================+ +========================+========+========================+
| $.absent1 == $.absent2 | true | Empty nodelists | | $.absent1 == $.absent2 | true | Empty nodelists |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.absent1 <= $.absent2 | true | == implies <= | | $.absent1 <= $.absent2 | true | == implies <= |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.absent == 'g' | false | Empty nodelist | | $.absent == 'g' | false | Empty nodelist |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.absent1 != $.absent2 | false | Empty nodelists | | $.absent1 != $.absent2 | false | Empty nodelists |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.absent != 'g' | true | Empty nodelist | | $.absent != 'g' | true | Empty nodelist |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| 1 <= 2 | true | Numeric comparison | | 1 <= 2 | true | Numeric comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| 1 > 2 | false | Strict, numeric comparison | | 1 > 2 | false | Numeric comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| 13 == '13' | false | Type mismatch | | 13 == '13' | false | Type mismatch |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| 'a' <= 'b' | true | String comparison | | 'a' <= 'b' | true | String comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| 'a' > 'b' | false | Strict, string comparison | | 'a' > 'b' | false | String comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.obj == $.arr | false | Type mismatch | | $.obj == $.arr | false | Type mismatch |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.obj != $.arr | true | Type mismatch | | $.obj != $.arr | true | Type mismatch |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.obj == $.obj | true | Object comparison | | $.obj == $.obj | true | Object comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.obj != $.obj | false | Object comparison | | $.obj != $.obj | false | Object comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.arr == $.arr | true | Array comparison | | $.arr == $.arr | true | Array comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.arr != $.arr | false | Array comparison | | $.arr != $.arr | false | Array comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.obj == 17 | false | Type mismatch | | $.obj == 17 | false | Type mismatch |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.obj != 17 | true | Type mismatch | | $.obj != 17 | true | Type mismatch |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.obj <= $.arr | false | Objects and arrays do not | | $.obj <= $.arr | false | Objects and arrays do |
| | | offer < comparison | | | | not offer < comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.obj < $.arr | false | Objects and arrays do not | | $.obj < $.arr | false | Objects and arrays do |
| | | offer < comparison | | | | not offer < comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.obj <= $.obj | true | == implies <= | | $.obj <= $.obj | true | == implies <= |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| $.arr <= $.arr | true | == implies <= | | $.arr <= $.arr | true | == implies <= |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| 1 <= $.arr | false | Arrays do not offer < | | 1 <= $.arr | false | Arrays do not offer < |
| | | comparison | | | | comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| 1 >= $.arr | false | Arrays do not offer < | | 1 >= $.arr | false | Arrays do not offer < |
| | | comparison | | | | comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| 1 > $.arr | false | Arrays do not offer < | | 1 > $.arr | false | Arrays do not offer < |
| | | comparison | | | | comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| 1 < $.arr | false | Arrays do not offer < | | 1 < $.arr | false | Arrays do not offer < |
| | | comparison | | | | comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| true <= true | true | == implies <= | | true <= true | true | == implies <= |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
| true > true | false | Booleans do not offer < | | true > true | false | Booleans do not offer |
| | | comparison | | | | < comparison |
+------------------------+--------+----------------------------+ +------------------------+--------+------------------------+
Table 11: Comparison examples Table 11: Comparison Examples
The second set of examples shows some complete JSONPath queries that The second set of examples shows some complete JSONPath queries that
make use of filter selectors, and the results of evaluating these make use of filter selectors and the results of evaluating these
queries on a given JSON value as input. (Note: two of the queries queries on a given JSON value as input. (Note: Two of the queries
employ function extensions; please see Sections 2.4.6 and 2.4.7 below employ function extensions; please see Sections 2.4.6 and 2.4.7 for
for details about these.) details about these.)
JSON: JSON:
{ {
"a": [3, 5, 1, 2, 4, 6, "a": [3, 5, 1, 2, 4, 6,
{"b": "j"}, {"b": "j"},
{"b": "k"}, {"b": "k"},
{"b": {}}, {"b": {}},
{"b": "kilo"} {"b": "kilo"}
], ],
"o": {"p": 1, "q": 2, "r": 3, "s": 5, "t": {"u": 6}}, "o": {"p": 1, "q": 2, "r": 3, "s": 5, "t": {"u": 6}},
"e": "f" "e": "f"
} }
Queries: Queries:
The examples in Table 12 show the filter selector in use by a child The examples in Table 12 show the filter selector in use by a child
segment: segment.
+==================+==============+=============+===================+ +==================+==============+=============+===================+
| Query | Result | Result | Comment | | Query | Result | Result | Comment |
| | | Paths | | | | | Paths | |
+==================+==============+=============+===================+ +==================+==============+=============+===================+
| $.a[?@.b == | {"b": | $['a'][9] | Member value | | $.a[?@.b == | {"b": | $['a'][9] | Member value |
| 'kilo'] | "kilo"} | | comparison | | 'kilo'] | "kilo"} | | comparison |
+------------------+--------------+-------------+-------------------+ +------------------+--------------+-------------+-------------------+
| $.a[?(@.b == | {"b": | $['a'][9] | Equivalent query | | $.a[?(@.b == | {"b": | $['a'][9] | Equivalent query |
| 'kilo')] | "kilo"} | | with enclosing | | 'kilo')] | "kilo"} | | with enclosing |
skipping to change at page 38, line 45 skipping to change at line 1676
| | 2 | $['a'][3] | | | | 2 | $['a'][3] | |
| | 4 | $['a'][4] | | | | 4 | $['a'][4] | |
| | 6 | $['a'][5] | | | | 6 | $['a'][5] | |
| | {"b": "j"} | $['a'][6] | | | | {"b": "j"} | $['a'][6] | |
| | {"b": "k"} | $['a'][7] | | | | {"b": "k"} | $['a'][7] | |
| | {"b": {}} | $['a'][8] | | | | {"b": {}} | $['a'][8] | |
| | {"b": | $['a'][9] | | | | {"b": | $['a'][9] | |
| | "kilo"} | | | | | "kilo"} | | |
+------------------+--------------+-------------+-------------------+ +------------------+--------------+-------------+-------------------+
Table 12: Filter selector examples Table 12: Filter Selector Examples
The example above with the query $.o[?@<3, ?@<3] shows that a filter The example above with the query $.o[?@<3, ?@<3] shows that a filter
selector may produce nodelists in distinct orders each time it selector may produce nodelists in distinct orders each time it
appears in the child segment. appears in the child segment.
2.4. Function Extensions 2.4. Function Extensions
Beyond the filter expression functionality defined in the preceding Beyond the filter expression functionality defined in the preceding
subsections, JSONPath defines an extension point that can be used to subsections, JSONPath defines an extension point that can be used to
add filter expression functionality: "Function Extensions". add filter expression functionality: "Function Extensions".
This section defines the extension point as well as some function This section defines the extension point and some function extensions
extensions that use this extension point. While these mechanisms are that use this extension point. While these mechanisms are designed
designed to use the extension point, they are an integral part of the to use the extension point, they are an integral part of the JSONPath
JSONPath specification and are expected to be implemented like any specification and are expected to be implemented like any other
other integral part of this specification. integral part of this specification.
A function extension defines a registered name (see Section 3.2) that A function extension defines a registered name (see Section 3.2) that
can be applied to a sequence of zero or more arguments, producing a can be applied to a sequence of zero or more arguments, producing a
result. Each registered function name is unique. result. Each registered function name is unique.
A function extension MUST be defined such that its evaluation is A function extension MUST be defined such that its evaluation is free
side-effect free, i.e., all possible orders of evaluation and choices of side effects, i.e., all possible orders of evaluation and choices
of short-circuiting or full evaluation of an expression containing it of short-circuiting or full evaluation of an expression containing it
MUST lead to the same result. (Note: memoization or logging are not MUST lead to the same result. (Note: Memoization or logging are not
side effects in this sense as they are visible at the implementation side effects in this sense as they are visible at the implementation
level only — they do not influence the result of the evaluation.) level only -- they do not influence the result of the evaluation.)
function-name = function-name-first *function-name-char function-name = function-name-first *function-name-char
function-name-first = LCALPHA function-name-first = LCALPHA
function-name-char = function-name-first / "_" / DIGIT function-name-char = function-name-first / "_" / DIGIT
LCALPHA = %x61-7A ; "a".."z" LCALPHA = %x61-7A ; "a".."z"
function-expr = function-name "(" S [function-argument function-expr = function-name "(" S [function-argument
*(S "," S function-argument)] S ")" *(S "," S function-argument)] S ")"
function-argument = literal / function-argument = literal /
filter-query / ; (includes singular-query) filter-query / ; (includes singular-query)
logical-expr / logical-expr /
function-expr function-expr
Any function expressions in a query must be well-formed (by Any function expressions in a query must be well-formed (by
conforming to the above ABNF) and well-typed, otherwise the JSONPath conforming to the above ABNF) and well-typed; otherwise, the JSONPath
implementation MUST raise an error (see Section 2.1). To define implementation MUST raise an error (see Section 2.1). To define
which function expressions are well-typed, a type system is first which function expressions are well-typed, a type system is first
introduced. introduced.
2.4.1. Type System for Function Expressions 2.4.1. Type System for Function Expressions
Each parameter as well as the result of a function extension must Each parameter and the result of a function extension must have a
have a declared type. declared type.
Declared types enable checking a JSONPath query for well-typedness Declared types enable checking a JSONPath query for well-typedness
independent of any query argument the JSONPath query is applied to. independent of any query argument the JSONPath query is applied to.
Table 13 defines the available types in terms of the instances they Table 13 defines the available types in terms of the instances they
contain. contain.
+=============+=============================+ +=============+=============================+
| Type | Instances | | Type | Instances |
+=============+=============================+ +=============+=============================+
| ValueType | JSON values or Nothing | | ValueType | JSON values or Nothing |
+-------------+-----------------------------+ +-------------+-----------------------------+
| LogicalType | LogicalTrue or LogicalFalse | | LogicalType | LogicalTrue or LogicalFalse |
+-------------+-----------------------------+ +-------------+-----------------------------+
| NodesType | Nodelists | | NodesType | Nodelists |
+-------------+-----------------------------+ +-------------+-----------------------------+
Table 13: Function extension type system Table 13: Function Extension Type System
Notes: Notes:
* The only instances that can be directly represented in JSONPath * The only instances that can be directly represented in JSONPath
syntax are certain JSON values in ValueType expressed as literals syntax are certain JSON values in ValueType expressed as literals
(which, in JSONPath, are limited to primitive values). (which, in JSONPath, are limited to primitive values).
* The special result Nothing represents the absence of a JSON value * The special result Nothing represents the absence of a JSON value
and is distinct from any JSON value, including null. and is distinct from any JSON value, including null.
skipping to change at page 41, line 19 skipping to change at line 1791
parameter of type NodesType and returns a result of type parameter of type NodesType and returns a result of type
ValueType. ValueType.
The well-typedness of function expressions can now be defined in The well-typedness of function expressions can now be defined in
terms of this type system. terms of this type system.
2.4.3. Well-Typedness of Function Expressions 2.4.3. Well-Typedness of Function Expressions
For a function expression to be well-typed: For a function expression to be well-typed:
1. its declared type must be well-typed in the context in which it 1. Its declared type must be well-typed in the context in which it
occurs, and occurs.
2. its arguments must be well-typed for the declared type of the As per the grammar, a function expression can occur in three
corresponding parameters. different immediate contexts, which lead to the following
conditions for well-typedness:
(1) As per the grammar, a function expression can occur in three As a test-expr in a logical expression:
different immediate contexts, which lead to the following conditions The function's declared result type is LogicalType or (giving
for well-typedness: rise to conversion as per Section 2.4.2) NodesType.
As a test-expr in a logical expression: As a comparable in a comparison:
The function's declared result type is LogicalType, or (giving The function's declared result type is ValueType.
rise to conversion as per Section 2.4.2) NodesType.
As a comparable in a comparison: As a function-argument in another function expression:
The function's declared result type is ValueType. The function's declared result type fulfills the following
rules for the corresponding parameter of the enclosing
function.
As a function-argument in another function expression: 2. Its arguments must be well-typed for the declared type of the
The function's declared result type fulfills the following rules corresponding parameters.
for the corresponding parameter of the enclosing function.
(2) The arguments of the function expression are well-typed when each The arguments of the function expression are well-typed when each
argument of the function can be used for the declared type of the argument of the function can be used for the declared type of the
corresponding parameter, according to one of the following corresponding parameter, according to one of the following
conditions: conditions:
* When the argument is a function expression with declared result * When the argument is a function expression with the same
type the same as the declared type of the parameter. declared result type as the declared type of the parameter.
* When the declared type of the parameter is LogicalType and the * When the declared type of the parameter is LogicalType and the
argument is one of the following: argument is one of the following:
- A function expression with declared result type NodesType. In - A function expression with declared result type NodesType.
this case the argument is converted to LogicalType as per In this case, the argument is converted to LogicalType as
Section 2.4.2. per Section 2.4.2.
- A logical-expr that is not a function expression. - A logical-expr that is not a function expression.
* When the declared type of the parameter is NodesType and the * When the declared type of the parameter is NodesType and the
argument is a query (which includes singular query). argument is a query (which includes singular query).
* When the declared type of the parameter is ValueType and the * When the declared type of the parameter is ValueType and the
argument is one of the following: argument is one of the following:
- A value expressed as a literal. - A value expressed as a literal.
- A singular query. In this case: - A singular query. In this case:
o If the query results in a nodelist consisting of a single o If the query results in a nodelist consisting of a
node, the argument is the value of the node. single node, the argument is the value of the node.
o If the query results in an empty nodelist, the argument is o If the query results in an empty nodelist, the argument
the special result Nothing. is the special result Nothing.
2.4.4. length() Function Extension 2.4.4. length() Function Extension
Parameters: Parameters:
1. ValueType 1. ValueType
Result: ValueType (unsigned integer or Nothing) Result: ValueType (unsigned integer or Nothing)
The length() function extension provides a way to compute the length The length() function extension provides a way to compute the length
of a value and make that available for further processing in the of a value and make that available for further processing in the
filter expression: filter expression:
$[?length(@.authors) >= 5] $[?length(@.authors) >= 5]
Its only argument is an instance of ValueType (possibly taken from a Its only argument is an instance of ValueType (possibly taken from a
singular query, as in the example above). The result also is an singular query, as in the example above). The result is also an
instance of ValueType: an unsigned integer or the special result instance of ValueType: an unsigned integer or the special result
Nothing. Nothing.
* If the argument value is a string, the result is the number of * If the argument value is a string, the result is the number of
Unicode scalar values in the string. Unicode scalar values in the string.
* If the argument value is an array, the result is the number of * If the argument value is an array, the result is the number of
elements in the array. elements in the array.
* If the argument value is an object, the result is the number of * If the argument value is an object, the result is the number of
skipping to change at page 43, line 21 skipping to change at line 1889
1. NodesType 1. NodesType
Result: ValueType (unsigned integer) Result: ValueType (unsigned integer)
The count() function extension provides a way to obtain the number of The count() function extension provides a way to obtain the number of
nodes in a nodelist and make that available for further processing in nodes in a nodelist and make that available for further processing in
the filter expression: the filter expression:
$[?count(@.*.author) >= 5] $[?count(@.*.author) >= 5]
Its only argument is a nodelist. The result is a value, an unsigned Its only argument is a nodelist. The result is a value (an unsigned
integer, that gives the number of nodes in the nodelist. Notes: integer) that gives the number of nodes in the nodelist.
Notes:
* There is no deduplication of the nodelist. * There is no deduplication of the nodelist.
* The number of nodes in the nodelist is counted independent of * The number of nodes in the nodelist is counted independent of
their values or any children they may have; e.g., the count of a their values or any children they may have, e.g., the count of a
non-empty singular nodelist such as count(@) is always 1. non-empty singular nodelist such as count(@) is always 1.
2.4.6. match() Function Extension 2.4.6. match() Function Extension
Parameters: Parameters:
1. ValueType (string) 1. ValueType (string)
2. ValueType (string conforming to 2. ValueType (string conforming to [RFC9485])
[I-D.draft-ietf-jsonpath-iregexp])
Result: LogicalType Result: LogicalType
The match() function extension provides a way to check whether (the The match() function extension provides a way to check whether (the
entirety of, see Section 2.4.7 below) a given string matches a given entirety of; see Section 2.4.7) a given string matches a given
regular expression, which is in [I-D.draft-ietf-jsonpath-iregexp] regular expression, which is in the form described in [RFC9485].
form.
$[?match(@.date, "1974-05-..")] $[?match(@.date, "1974-05-..")]
Its arguments are instances of ValueType (possibly taken from a Its arguments are instances of ValueType (possibly taken from a
singular query, as for the first argument in the example above). If singular query, as for the first argument in the example above). If
the first argument is not a string or the second argument is not a the first argument is not a string or the second argument is not a
string conforming to [I-D.draft-ietf-jsonpath-iregexp], the result is string conforming to [RFC9485], the result is LogicalFalse.
LogicalFalse. Otherwise, the string that is the first argument is Otherwise, the string that is the first argument is matched against
matched against the iregexp contained in the string that is the the I-Regexp contained in the string that is the second argument; the
second argument; the result is LogicalTrue if the string matches the result is LogicalTrue if the string matches the I-Regexp and is
iregexp and LogicalFalse otherwise. LogicalFalse otherwise.
2.4.7. search() Function Extension 2.4.7. search() Function Extension
Parameters: Parameters:
1. ValueType (string) 1. ValueType (string)
2. ValueType (string conforming to 2. ValueType (string conforming to [RFC9485])
[I-D.draft-ietf-jsonpath-iregexp])
Result: LogicalType Result: LogicalType
The search() function extension provides a way to check whether a The search() function extension provides a way to check whether a
given string contains a substring that matches a given regular given string contains a substring that matches a given regular
expression, which is in [I-D.draft-ietf-jsonpath-iregexp] form. expression, which is in the form described in [RFC9485].
$[?search(@.author, "[BR]ob")] $[?search(@.author, "[BR]ob")]
Its arguments are instances of ValueType (possibly taken from a Its arguments are instances of ValueType (possibly taken from a
singular query, as for the first argument in the example above). If singular query, as for the first argument in the example above). If
the first argument is not a string or the second argument is not a the first argument is not a string or the second argument is not a
string conforming to [I-D.draft-ietf-jsonpath-iregexp], the result is string conforming to [RFC9485], the result is LogicalFalse.
LogicalFalse. Otherwise, the string that is the first argument is Otherwise, the string that is the first argument is searched for a
searched for at least one substring that matches the iregexp substring that matches the I-Regexp contained in the string that is
contained in the string that is the second argument; the result is the second argument; the result is LogicalTrue if at least one such
LogicalTrue if such a substring exists and LogicalFalse otherwise. substring exists and is LogicalFalse otherwise.
2.4.8. value() Function Extension 2.4.8. value() Function Extension
Parameters: Parameters:
1. NodesType 1. NodesType
Result: ValueType Result: ValueType
The value() function extension provides a way to convert an instance The value() function extension provides a way to convert an instance
of NodesType to a value and make that available for further of NodesType to a value and make that available for further
skipping to change at page 45, line 4 skipping to change at line 1960
Parameters: Parameters:
1. NodesType 1. NodesType
Result: ValueType Result: ValueType
The value() function extension provides a way to convert an instance The value() function extension provides a way to convert an instance
of NodesType to a value and make that available for further of NodesType to a value and make that available for further
processing in the filter expression: processing in the filter expression:
$[?value(@..color) == "red"] $[?value(@..color) == "red"]
Its only argument is an instance of NodesType (possibly taken from a Its only argument is an instance of NodesType (possibly taken from a
filter-query, as in the example above). The result is an instance of filter-query, as in the example above). The result is an instance of
ValueType. ValueType.
* If the argument contains a single node, the result is the value of * If the argument contains a single node, the result is the value of
the node. the node.
* If the argument is the special result Nothing or contains multiple * If the argument is the empty nodelist or contains multiple nodes,
nodes, the result is Nothing. the result is Nothing.
Note: a singular query may be used anywhere where a ValueType is Note: A singular query may be used anywhere where a ValueType is
expected, so there is no need to use the value() function extension expected, so there is no need to use the value() function extension
with a singular query. with a singular query.
2.4.9. Examples 2.4.9. Examples
+======================+==========================================+ +======================+==========================================+
| Query | Comment | | Query | Comment |
+======================+==========================================+ +======================+==========================================+
| $[?length(@) < 3] | well-typed | | $[?length(@) < 3] | well-typed |
+----------------------+------------------------------------------+ +----------------------+------------------------------------------+
skipping to change at page 46, line 23 skipping to change at line 2028
+----------------------+------------------------------------------+ +----------------------+------------------------------------------+
| $[?blt(1)] | not well-typed for the same function | | $[?blt(1)] | not well-typed for the same function |
| | blt(), as 1 is not a query, logical- | | | blt(), as 1 is not a query, logical- |
| | expr, or function expression | | | expr, or function expression |
+----------------------+------------------------------------------+ +----------------------+------------------------------------------+
| $[?bal(1)] | well-typed, where bal() is a function | | $[?bal(1)] | well-typed, where bal() is a function |
| | with a parameter of declared type | | | with a parameter of declared type |
| | ValueType and result type LogicalType | | | ValueType and result type LogicalType |
+----------------------+------------------------------------------+ +----------------------+------------------------------------------+
Table 14: Function expression examples Table 14: Function Expression Examples
2.5. Segments 2.5. Segments
For each node in an input nodelist, segments apply one or more For each node in an input nodelist, segments apply one or more
selectors to the node and concatenate the results of each selector selectors to the node and concatenate the results of each selector
into per-input-node nodelists, which are then concatenated in the into per-input-node nodelists, which are then concatenated in the
order of the input nodelist to form a single segment result nodelist. order of the input nodelist to form a single segment result nodelist.
It turns out that the more segments there are in a query, the greater It turns out that the more segments there are in a query, the greater
the depth in the input value of the nodes of the resultant nodelist: the depth in the input value of the nodes of the resultant nodelist:
* A query with N segments, where N >= 0, produces a nodelist * A query with N segments, where N >= 0, produces a nodelist
consisting of nodes at depth in the input value of N or greater. consisting of nodes at depth in the input value of N or greater.
* A query with N segments, where N >= 0, all of which are child * A query with N segments, where N >= 0, all of which are child
segments (Section 2.5.1), produces a nodelist consisting of nodes segments (Section 2.5.1), produces a nodelist consisting of nodes
precisely at depth N in the input value. precisely at depth N in the input value.
There are two kinds of segment: child segments and descendant There are two kinds of segments: child segments and descendant
segments. segments.
segment = child-segment / descendant-segment segment = child-segment / descendant-segment
The syntax and semantics of each kind of segment are defined below. The syntax and semantics of each kind of segment are defined below.
2.5.1. Child Segment 2.5.1. Child Segment
2.5.1.1. Syntax 2.5.1.1. Syntax
skipping to change at page 47, line 25 skipping to change at line 2074
child-segment = bracketed-selection / child-segment = bracketed-selection /
("." ("."
(wildcard-selector / (wildcard-selector /
member-name-shorthand)) member-name-shorthand))
bracketed-selection = "[" S selector *(S "," S selector) S "]" bracketed-selection = "[" S selector *(S "," S selector) S "]"
member-name-shorthand = name-first *name-char member-name-shorthand = name-first *name-char
name-first = ALPHA / name-first = ALPHA /
"_" / "_" /
%x80-D7FF / ; skip surrogate code points %x80-D7FF /
; skip surrogate code points
%xE000-10FFFF %xE000-10FFFF
name-char = DIGIT / name-first name-char = name-first / DIGIT
DIGIT = %x30-39 ; 0-9 DIGIT = %x30-39 ; 0-9
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
.*, a child-segment directly built from a wildcard-selector, is .*, a child-segment directly built from a wildcard-selector, is
shorthand for [*]. shorthand for [*].
.<member-name>, a child-segment built from a member-name-shorthand, .<member-name>, a child-segment built from a member-name-shorthand,
is shorthand for ['<member-name>']. Note: this can only be used with is shorthand for ['<member-name>']. Note: This can only be used with
member names that are composed of certain characters, as specified in member names that are composed of certain characters, as specified in
the ABNF rule member-name-shorthand. Thus, for example, $.foo.bar is the ABNF rule member-name-shorthand. Thus, for example, $.foo.bar is
shorthand for $['foo']['bar'] (but not for $['foo.bar']). shorthand for $['foo']['bar'] (but not for $['foo.bar']).
2.5.1.2. Semantics 2.5.1.2. Semantics
A child segment contains a sequence of selectors, each of which A child segment contains a sequence of selectors, each of which
selects zero or more children of the input value. selects zero or more children of the input value.
Selectors of different kinds may be combined within a single child Selectors of different kinds may be combined within a single child
segment. segment.
For each node in the input nodelist, the resulting nodelist of a For each node in the input nodelist, the resulting nodelist of a
child segment is the concatenation of the nodelists from each of its child segment is the concatenation of the nodelists from each of its
selectors in the order that the selectors appear in the list. Note: selectors in the order that the selectors appear in the list. Note:
any node matched by more than one selector is kept as many times in Any node matched by more than one selector is kept as many times in
the nodelist. the nodelist.
Where a selector can produce a nodelist in more than one possible Where a selector can produce a nodelist in more than one possible
order, each occurrence of the selector in the child segment may order, each occurrence of the selector in the child segment may
evaluate to produce a nodelist in a distinct order. produce a nodelist in a distinct order.
So a child segment drills down one more level into the structure of In summary, a child segment drills down one more level into the
the input value. structure of the input value.
2.5.1.3. Examples 2.5.1.3. Examples
JSON: JSON:
["a", "b", "c", "d", "e", "f", "g"] ["a", "b", "c", "d", "e", "f", "g"]
Queries: Queries:
+========+========+========+============+ +========+========+========+============+
skipping to change at page 48, line 41 skipping to change at line 2135
| 3] | "d" | $[3] | | | 3] | "d" | $[3] | |
+--------+--------+--------+------------+ +--------+--------+--------+------------+
| $[0:2, | "a" | $[0] | Slice and | | $[0:2, | "a" | $[0] | Slice and |
| 5] | "b" | $[1] | index | | 5] | "b" | $[1] | index |
| | "f" | $[5] | | | | "f" | $[5] | |
+--------+--------+--------+------------+ +--------+--------+--------+------------+
| $[0, | "a" | $[0] | Duplicated | | $[0, | "a" | $[0] | Duplicated |
| 0] | "a" | $[0] | entries | | 0] | "a" | $[0] | entries |
+--------+--------+--------+------------+ +--------+--------+--------+------------+
Table 15: Child segment examples Table 15: Child Segment Examples
2.5.2. Descendant Segment 2.5.2. Descendant Segment
2.5.2.1. Syntax 2.5.2.1. Syntax
The descendant segment consists of a double dot .. followed by a The descendant segment consists of a double dot .. followed by a
child segment (using bracket notation). child segment (using bracket notation).
Shortand notations are also provided that correspond to the shorthand Shorthand notations are also provided that correspond to the
forms of the child segment. shorthand forms of the child segment.
descendant-segment = ".." (bracketed-selection / descendant-segment = ".." (bracketed-selection /
wildcard-selector / wildcard-selector /
member-name-shorthand) member-name-shorthand)
..*, the descendant-segment directly built from a wildcard-selector, ..*, the descendant-segment directly built from a wildcard-selector,
is shorthand for ..[*]. is shorthand for ..[*].
..<member-name>, a descendant-segment built from a member-name- ..<member-name>, a descendant-segment built from a member-name-
shorthand, is shorthand for ..['<member-name>']. Note: as with the shorthand, is shorthand for ..['<member-name>']. Note: As with the
similar shorthand of a child-segment, this can only be used with similar shorthand of a child-segment, this can only be used with
member names that are composed of certain characters, as specified in member names that are composed of certain characters, as specified in
the ABNF rule member-name-shorthand. the ABNF rule member-name-shorthand.
Note: .. on its own is not a valid segment. Note: On its own, .. is not a valid segment.
2.5.2.2. Semantics 2.5.2.2. Semantics
A descendant segment produces zero or more descendants of an input A descendant segment produces zero or more descendants of an input
value. value.
For each node in the input nodelist, a descendant selector visits the For each node in the input nodelist, a descendant selector visits the
input node and each of its descendants such that: input node and each of its descendants such that:
* nodes of any array are visited in array order, and * nodes of any array are visited in array order, and
* nodes are visited before their descendants. * nodes are visited before their descendants.
The order in which the children of an object are visited is not The order in which the children of an object are visited is not
stipulated, since JSON objects are unordered. stipulated, since JSON objects are unordered.
Suppose the descendant segment is of the form ..[<selectors>] (after Suppose the descendant segment is of the form ..[<selectors>] (after
converting any shorthand form to bracket notation) and the nodes, in converting any shorthand form to bracket notation), and the nodes, in
the order visited, are D1, ..., Dn (where n >= 1). Note: D1 is the the order visited, are D1, ..., Dn (where n >= 1). Note: D1 is the
input value. input value.
For each i such that 1 <= i <= n, the nodelist Ri is defined to be a For each i such that 1 <= i <= n, the nodelist Ri is defined to be a
result of applying the child segment [<selectors>] to the node Di. result of applying the child segment [<selectors>] to the node Di.
For each node in the input nodelist, the result of the descendant For each node in the input nodelist, the result of the descendant
segment is the concatenation of R1, ..., Rn (in that order). These segment is the concatenation of R1, ..., Rn (in that order). These
results are then concatenated in input nodelist order to form the results are then concatenated in input nodelist order to form the
result of the segment. result of the segment.
So a descendant segment drills down one or more levels into the In summary, a descendant segment drills down one or more levels into
structure of each input value. the structure of each input value.
2.5.2.3. Examples 2.5.2.3. Examples
JSON: JSON:
{ {
"o": {"j": 1, "k": 2}, "o": {"j": 1, "k": 2},
"a": [5, 3, [{"j": 4}, {"k": 6}]] "a": [5, 3, [{"j": 4}, {"k": 6}]]
} }
Queries: Queries:
(Note that the fourth example can be expressed in two equivalent (Note that the fourth example can be expressed in two equivalent
queries, shown here in one table row instead of two almost identical queries, shown in Table 16 in one table row instead of two almost-
rows.) identical rows.)
+==========+================+===================+===================+ +==========+================+===================+===================+
| Query | Result | Result Paths | Comment | | Query | Result | Result Paths | Comment |
+==========+================+===================+===================+ +==========+================+===================+===================+
| $..j | 1 | $['o']['j'] | Object values | | $..j | 1 | $['o']['j'] | Object values |
| | 4 | $['a'][2][0]['j'] | | | | 4 | $['a'][2][0]['j'] | |
+----------+----------------+-------------------+-------------------+ +----------+----------------+-------------------+-------------------+
| $..j | 4 | $['a'][2][0]['j'] | Alternative | | $..j | 4 | $['a'][2][0]['j'] | Alternative |
| | 1 | $['o']['j'] | result | | | 1 | $['o']['j'] | result |
+----------+----------------+-------------------+-------------------+ +----------+----------------+-------------------+-------------------+
| $..[0] | 5 | $['a'][0] | Array values | | $..[0] | 5 | $['a'][0] | Array values |
skipping to change at page 51, line 46 skipping to change at line 2250
| *] | 2 | $['o']['k'] | ordering | | *] | 2 | $['o']['k'] | ordering |
| | 2 | $['o']['k'] | | | | 2 | $['o']['k'] | |
| | 1 | $['o']['j'] | | | | 1 | $['o']['j'] | |
+----------+----------------+-------------------+-------------------+ +----------+----------------+-------------------+-------------------+
| $.a..[0, | 5 | $['a'][0] | Multiple segments | | $.a..[0, | 5 | $['a'][0] | Multiple segments |
| 1] | 3 | $['a'][1] | | | 1] | 3 | $['a'][1] | |
| | {"j": 4} | $['a'][2][0] | | | | {"j": 4} | $['a'][2][0] | |
| | {"k": 6} | $['a'][2][1] | | | | {"k": 6} | $['a'][2][1] | |
+----------+----------------+-------------------+-------------------+ +----------+----------------+-------------------+-------------------+
Table 16: Descendant segment examples Table 16: Descendant Segment Examples
Note: the ordering of the results for the $..[*] and $..* examples Note: The ordering of the results for the $..[*] and $..* examples
above is not guaranteed, except that: above is not guaranteed, except that:
* {"j": 1, "k": 2} must appear before 1 and 2, * {"j": 1, "k": 2} must appear before 1 and 2,
* [5, 3, [{"j": 4}, {"k": 6}]] must appear before 5, 3, and [{"j": * [5, 3, [{"j": 4}, {"k": 6}]] must appear before 5, 3, and [{"j":
4}, {"k": 6}], 4}, {"k": 6}],
* 5 must appear before 3 which must appear before [{"j": 4}, {"k": * 5 must appear before 3, which must appear before [{"j": 4}, {"k":
6}], 6}],
* 5 and 3 must appear before {"j": 4}, 4, , {"k": 6}, and 6, * 5 and 3 must appear before {"j": 4}, 4, {"k": 6}, and 6,
* [{"j": 4}, {"k": 6}] must appear before {"j": 4} and {"k": 6}, * [{"j": 4}, {"k": 6}] must appear before {"j": 4} and {"k": 6},
* {"j": 4} must appear before {"k": 6}, * {"j": 4} must appear before {"k": 6},
* {"k": 6} must appear before 4, and * {"k": 6} must appear before 4, and
* 4 must appear before 6. * 4 must appear before 6.
The example above with the query $.o..[*, *] shows that a selector The example above with the query $.o..[*, *] shows that a selector
may produce nodelists in distinct orders each time it appears in the may produce nodelists in distinct orders each time it appears in the
descendant segment. descendant segment.
The example above with the query $.a..[0, 1] shows that the child The example above with the query $.a..[0, 1] shows that the child
segment [0, 1] is applied to each node in turn (rather than the nodes segment [0, 1] is applied to each node in turn (rather than the nodes
being visited once per selector, which is the case for some JSONPath being visited once per selector, which is the case for some JSONPath
implementations that do not conform to this specification). implementations that do not conform to this specification).
2.6. Semantics of null 2.6. Semantics of null
Note: JSON null is treated the same as any other JSON value: it is Note: JSON null is treated the same as any other JSON value, i.e., it
not taken to mean "undefined" or "missing". is not taken to mean "undefined" or "missing".
2.6.1. Examples 2.6.1. Examples
JSON: JSON:
{"a": null, "b": [null], "c": [{}], "null": 1} {"a": null, "b": [null], "c": [{}], "null": 1}
Queries: Queries:
+=================+========+===========+===========================+ +=================+========+===========+===========================+
skipping to change at page 53, line 30 skipping to change at line 2320
+-----------------+--------+-----------+---------------------------+ +-----------------+--------+-----------+---------------------------+
| $.b[?@==null] | null | $['b'][0] | Comparison | | $.b[?@==null] | null | $['b'][0] | Comparison |
+-----------------+--------+-----------+---------------------------+ +-----------------+--------+-----------+---------------------------+
| $.c[?@.d==null] | | | Comparison with "missing" | | $.c[?@.d==null] | | | Comparison with "missing" |
| | | | value | | | | | value |
+-----------------+--------+-----------+---------------------------+ +-----------------+--------+-----------+---------------------------+
| $.null | 1 | $['null'] | Not JSON null at all, | | $.null | 1 | $['null'] | Not JSON null at all, |
| | | | just a member name string | | | | | just a member name string |
+-----------------+--------+-----------+---------------------------+ +-----------------+--------+-----------+---------------------------+
Table 17: Examples involving (or not involving) null Table 17: Examples Involving (or Not Involving) null
2.7. Normalized Paths 2.7. Normalized Paths
A Normalized Path is a unique representation of the location of a A Normalized Path is a unique representation of the location of a
node in a value which uniquely identifies the node in the value. node in a value that uniquely identifies the node in the value.
Specifically, a Normalized Path is a JSONPath query with restricted Specifically, a Normalized Path is a JSONPath query with restricted
syntax (defined below), e.g., $['book'][3], which when applied to the syntax (defined below), e.g., $['book'][3], which when applied to the
value results in a nodelist consisting of just the node identified by value, results in a nodelist consisting of just the node identified
the Normalized Path. Note: a Normalized Path represents the identity by the Normalized Path. Note: A Normalized Path represents the
of a node _in a specific value_. There is precisely one Normalized identity of a node _in a specific value_. There is precisely one
Path identifying any particular node in a value. Normalized Path identifying any particular node in a value.
A nodelist may be represented compactly in JSON as an array of A nodelist may be represented compactly in JSON as an array of
strings, where the strings are Normalized Paths. strings, where the strings are Normalized Paths.
Normalized Paths provide a predictable format that simplifies testing Normalized Paths provide a predictable format that simplifies testing
and post-processing of nodelists, e.g., to remove duplicate nodes. and post-processing of nodelists, e.g., to remove duplicate nodes.
Normalized Paths are used in this document as result paths in Normalized Paths are used in this document as result paths in
examples. examples.
Normalized Paths use the canonical bracket notation, rather than dot Normalized Paths use the canonical bracket notation, rather than dot
notation. notation.
Single quotes are used in Normalized Paths to delimit string member Single quotes are used in Normalized Paths to delimit string member
names. This reduces the number of characters that need escaping when names. This reduces the number of characters that need escaping when
Normalized Paths appear in double quote-delimited strings, e.g., in Normalized Paths appear in strings delimited by double quotes, e.g.,
JSON texts. in JSON texts.
Certain characters are escaped in Normalized Paths, in one and only Certain characters are escaped in Normalized Paths in one and only
one way; all other characters are unescaped. one way; all other characters are unescaped.
Note: Normalized Paths are singular queries, but not all singular | Note: Normalized Paths are singular queries, but not all
queries are Normalized Paths. For example, $[-3] is a singular | singular queries are Normalized Paths. For example, $[-3] is a
query, but is not a Normalized Path. The Normalized Path equivalent | singular query but is not a Normalized Path. The Normalized
to $[-3] would have an index equal to the array length minus 3. (The | Path equivalent to $[-3] would have an index equal to the array
array length must be at least 3 if $[-3] is to identify a node.) | length minus 3. (The array length must be at least 3 if $[-3]
| is to identify a node.)
normalized-path = root-identifier *(normal-index-segment) normalized-path = root-identifier *(normal-index-segment)
normal-index-segment = "[" normal-selector "]" normal-index-segment = "[" normal-selector "]"
normal-selector = normal-name-selector / normal-index-selector normal-selector = normal-name-selector / normal-index-selector
normal-name-selector = %x27 *normal-single-quoted %x27 ; 'string' normal-name-selector = %x27 *normal-single-quoted %x27 ; 'string'
normal-single-quoted = normal-unescaped / normal-single-quoted = normal-unescaped /
ESC normal-escapable ESC normal-escapable
normal-unescaped = ; omit %x0-1F control codes normal-unescaped = ; omit %x0-1F control codes
%x20-26 / %x20-26 /
; omit 0x27 ' ; omit 0x27 '
%x28-5B / %x28-5B /
; omit 0x5C \ ; omit 0x5C \
%x5D-D7FF / ; skip surrogate code points %x5D-D7FF /
; skip surrogate code points
%xE000-10FFFF %xE000-10FFFF
normal-escapable = %x62 / ; b BS backspace U+0008 normal-escapable = %x62 / ; b BS backspace U+0008
%x66 / ; f FF form feed U+000C %x66 / ; f FF form feed U+000C
%x6E / ; n LF line feed U+000A %x6E / ; n LF line feed U+000A
%x72 / ; r CR carriage return U+000D %x72 / ; r CR carriage return U+000D
%x74 / ; t HT horizontal tab U+0009 %x74 / ; t HT horizontal tab U+0009
"'" / ; ' apostrophe U+0027 "'" / ; ' apostrophe U+0027
"\" / ; \ backslash (reverse solidus) U+005C "\" / ; \ backslash (reverse solidus) U+005C
(%x75 normal-hexchar) (%x75 normal-hexchar)
; certain values u00xx U+00XX ; certain values u00xx U+00XX
normal-hexchar = "0" "0" normal-hexchar = "0" "0"
( (
("0" %x30-37) / ; "00"-"07" ("0" %x30-37) / ; "00"-"07"
; omit U+0008-U+000A BS HT LF ; omit U+0008-U+000A BS HT LF
("0" %x62) / ; "0b" ("0" %x62) / ; "0b"
; omit U+000C-U+000D FF CR ; omit U+000C-U+000D FF CR
("0" %x65-66) / ; "0e"-"0f" ("0" %x65-66) / ; "0e"-"0f"
("1" normal-HEXDIG) ("1" normal-HEXDIG)
) )
normal-HEXDIG = DIGIT / %x61-66 ; "0"-"9", "a"-"f" normal-HEXDIG = DIGIT / %x61-66 ; "0"-"9", "a"-"f"
normal-index-selector = "0" / (DIGIT1 *DIGIT) normal-index-selector = "0" / (DIGIT1 *DIGIT)
; non-negative decimal integer ; non-negative decimal integer
Since there can only be one Normalized Path identifying a given node, Since there can only be one Normalized Path identifying a given node,
the syntax stipulates which characters are escaped and which are not. the syntax stipulates which characters are escaped and which are not.
So the definition of normal-hexchar is designed for hex escaping of So the definition of normal-hexchar is designed for hex escaping of
characters which are not straightforwardly printable, for example characters that are not straightforwardly printable, for example,
U+000B LINE TABULATION, but for which no standard JSON escape, such U+000B LINE TABULATION, but for which no standard JSON escape, such
as \n, is available. as \n, is available.
2.7.1. Examples 2.7.1. Examples
+=============+=================+==========================+ +=============+=================+==========================+
| Path | Normalized Path | Comment | | Path | Normalized Path | Comment |
+=============+=================+==========================+ +=============+=================+==========================+
| $.a | $['a'] | Object value | | $.a | $['a'] | Object value |
+-------------+-----------------+--------------------------+ +-------------+-----------------+--------------------------+
skipping to change at page 56, line 24 skipping to change at line 2422
| $[-3] | $[2] | Negative array index for | | $[-3] | $[2] | Negative array index for |
| | | an array of length 5 | | | | an array of length 5 |
+-------------+-----------------+--------------------------+ +-------------+-----------------+--------------------------+
| $.a.b[1:2] | $['a']['b'][1] | Nested structure | | $.a.b[1:2] | $['a']['b'][1] | Nested structure |
+-------------+-----------------+--------------------------+ +-------------+-----------------+--------------------------+
| $["\u000B"] | $['\u000b'] | Unicode escape | | $["\u000B"] | $['\u000b'] | Unicode escape |
+-------------+-----------------+--------------------------+ +-------------+-----------------+--------------------------+
| $["\u0061"] | $['a'] | Unicode character | | $["\u0061"] | $['a'] | Unicode character |
+-------------+-----------------+--------------------------+ +-------------+-----------------+--------------------------+
Table 18: Normalized Path examples Table 18: Normalized Path Examples
3. IANA Considerations 3. IANA Considerations
// RFC Ed.: throughout this section, please replace RFCXXXX with the
// RFC number of this specification and remove this note.
3.1. Registration of Media Type application/jsonpath 3.1. Registration of Media Type application/jsonpath
IANA is requested to register the following media type [RFC6838]: IANA has registered the following media type [RFC6838]:
Type name: application Type name: application
Subtype name: jsonpath Subtype name: jsonpath
Required parameters: N/A Required parameters: N/A
Optional parameters: N/A Optional parameters: N/A
Encoding considerations: binary (UTF-8) Encoding considerations: binary (UTF-8)
Security considerations: See the Security Considerations section of Security considerations: See the Security Considerations section of
RFCXXXX. RFC 9535.
Interoperability considerations: N/A Interoperability considerations: N/A
Published specification: RFCXXXX Published specification: RFC 9535
Applications that use this media type: Applications that need to Applications that use this media type: Applications that need to
convey queries in JSON data convey queries in JSON data
Fragment identifier considerations: N/A Fragment identifier considerations: N/A
Additional information: Deprecated alias names for this type: N/A Additional information:
Magic number(s): N/A
File extension(s): N/A
Macintosh file type code(s): N/A Deprecated alias names for this type: N/A
Magic number(s): N/A
File extension(s): N/A
Macintosh file type code(s): N/A
Person & email address to contact for further information: Person & email address to contact for further information:
iesg@ietf.org iesg@ietf.org
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: N/A Restrictions on usage: N/A
Author: JSONPath WG Author: JSONPath WG
Change controller: IETF Change controller: IETF
Provisional registration? (standards tree only): no 3.2. Function Extensions Subregistry
3.2. Function Extensions
This specification defines a new "Function Extensions sub-registry" Per this specification, IANA has created a new "Function Extensions"
in a new "JSONPath Parameters registry", with the policy "expert subregistry in a new "JSONPath" registry. The "Function Extensions"
review" (Section 4.5 of [BCP26]). subregistry has the policy "Expert Review" (Section 4.5 of
[RFC8126]).
The experts are instructed to be frugal in the allocation of function The experts are instructed to be frugal in the allocation of function
extension names that are suggestive of generally applicable extension names that are suggestive of generally applicable
semantics, keeping them in reserve for functions that are likely to semantics, keeping them in reserve for functions that are likely to
enjoy wide use and can make good use of their conciseness. The enjoy wide use and can make good use of their conciseness. The
expert is also instructed to direct the registrant to provide a expert is also instructed to direct the registrant to provide a
specification (Section 4.6 of [BCP26]), but can make exceptions, for specification (Section 4.6 of [RFC8126]) but can make exceptions, for
instance when a specification is not available at the time of instance, when a specification is not available at the time of
registration but is likely forthcoming. If the expert becomes aware registration but is likely forthcoming. If the expert becomes aware
of function extensions that are deployed and in use, they may also of function extensions that are deployed and in use, they may also
initiate a registration on their own if they deem such a registration initiate a registration on their own if they deem such a registration
can avert potential future collisions. can avert potential future collisions.
Each entry in the sub-registry must include: Each entry in the subregistry must include the following:
Function Name: Function Name:
A lowercase ASCII [RFC0020] string that starts with a letter and
a lower case ASCII [STD80] string that starts with a letter and can contain letters, digits, and underscore characters afterwards
can contain letters, digits and underscore characters afterwards ([a-z][_a-z0-9]*). No other entry in the subregistry can have the
([a-z][_a-z0-9]*). No other entry in the sub-registry can have same function name.
the same function name.
Brief description: Brief description:
a brief description A brief description
Parameters: Parameters:
A comma-separated list of zero or more declared types, one for A comma-separated list of zero or more declared types, one for
each of the arguments expected for this function extension each of the arguments expected for this function extension
Result: Result:
The declared type of the result for this function extension The declared type of the result for this function extension
Change Controller: Change Controller:
(see Section 2.3 of [BCP26]) See Section 2.3 of [RFC8126].
Reference: Reference:
a reference document that provides a description of the function A reference document that provides a description of the function
extension extension
Initial entries in this sub-registry are as listed in Table 19; the The initial entries in this subregistry are listed in Table 19; the
entries in the Column "Change Controller" all have the value "IETF" entries in the "Change Controller" column all have the value "IETF",
and the entries in the column "Reference" all have the value and the entries in the "Reference" column all have the value
"Section 2.4 of RFCXXXX": "Section 2.4 of RFC 9535":
+===============+====================+============+=============+ +===============+=====================+============+=============+
| Function Name | Brief description | Parameters | Result | | Function Name | Brief Description | Parameters | Result |
+===============+====================+============+=============+ +===============+=====================+============+=============+
| length | length of string, | ValueType | ValueType | | length | length of string, | ValueType | ValueType |
| | array, object | | | | | array, or object | | |
+---------------+--------------------+------------+-------------+ +---------------+---------------------+------------+-------------+
| count | size of nodelist | NodesType | ValueType | | count | size of nodelist | NodesType | ValueType |
+---------------+--------------------+------------+-------------+ +---------------+---------------------+------------+-------------+
| match | regular expression | ValueType, | LogicalType | | match | regular expression | ValueType, | LogicalType |
| | full match | ValueType | | | | full match | ValueType | |
+---------------+--------------------+------------+-------------+ +---------------+---------------------+------------+-------------+
| search | regular expression | ValueType, | LogicalType | | search | regular expression | ValueType, | LogicalType |
| | substring match | ValueType | | | | substring match | ValueType | |
+---------------+--------------------+------------+-------------+ +---------------+---------------------+------------+-------------+
| value | value of single | NodesType | ValueType | | value | value of the single | NodesType | ValueType |
| | node in nodelist | | | | | node in nodelist | | |
+---------------+--------------------+------------+-------------+ +---------------+---------------------+------------+-------------+
Table 19: Initial Entries in the Function Extensions Subregistry Table 19: Initial Entries in the Function Extensions Subregistry
4. Security Considerations 4. Security Considerations
Security considerations for JSONPath can stem from Security considerations for JSONPath can stem from:
* attack vectors on JSONPath implementations, * attack vectors on JSONPath implementations,
* attack vectors on how JSONPath queries are formed, and * attack vectors on how JSONPath queries are formed, and
* the way JSONPath is used in security-relevant mechanisms. * the way JSONPath is used in security-relevant mechanisms.
4.1. Attack Vectors on JSONPath Implementations 4.1. Attack Vectors on JSONPath Implementations
Historically, JSONPath has often been implemented by feeding parts of Historically, JSONPath has often been implemented by feeding parts of
skipping to change at page 59, line 29 skipping to change at line 2563
JavaScript's eval() function. This approach is well known to lead to JavaScript's eval() function. This approach is well known to lead to
injection attacks and would require perfect input validation to injection attacks and would require perfect input validation to
prevent these attacks (see Section 12 of [RFC8259] for similar prevent these attacks (see Section 12 of [RFC8259] for similar
considerations for JSON itself). Instead, JSONPath implementations considerations for JSON itself). Instead, JSONPath implementations
need to implement the entire syntax of the query without relying on need to implement the entire syntax of the query without relying on
the parsers of programming language engines. the parsers of programming language engines.
Attacks on availability may attempt to trigger unusually expensive Attacks on availability may attempt to trigger unusually expensive
runtime performance exhibited by certain implementations in certain runtime performance exhibited by certain implementations in certain
cases. (See Section 10 of [RFC8949] for issues in hash-table cases. (See Section 10 of [RFC8949] for issues in hash-table
implementations, and Section 8 of [I-D.draft-ietf-jsonpath-iregexp] implementations and Section 8 of [RFC9485] for performance issues in
for performance issues in regular expression implementations.) regular expression implementations.) Implementers need to be aware
Implementers need to be aware that good average performance is not that good average performance is not sufficient as long as an
sufficient as long as an attacker can choose to submit specially attacker can choose to submit specially crafted JSONPath queries or
crafted JSONPath queries or query arguments that trigger surprisingly query arguments that trigger surprisingly high, possibly exponential,
high, possibly exponential, CPU usage or, for example via a naive CPU usage or, for example, via a naive recursive implementation of
recursive implementation of the descendant segment, stack overflow. the descendant segment, stack overflow. Implementations need to have
Implementations need to have appropriate resource management to appropriate resource management to mitigate these attacks.
mitigate these attacks.
4.2. Attack Vectors on How JSONPath Queries are Formed 4.2. Attack Vectors on How JSONPath Queries Are Formed
JSONPath queries are often not static, but formed from variables that JSONPath queries are often not static but formed from variables that
provide index values, member names, or values to compare with in a provide index values, member names, or values to compare with in a
filter expression. These variables need to be validated (e.g., only filter expression. These variables need to be validated (e.g., only
allowing specific constructs such as .name to be formed when the allowing specific constructs such as .name to be formed when the
given values allow that) and translated (e.g., by escaping string given values allow that) and translated (e.g., by escaping string
delimiters). Not performing these validations and translations delimiters). Not performing these validations and translations
correctly can lead to unexpected failures, which can lead to correctly can lead to unexpected failures, which can lead to
Availability, Confidentiality, and Integrity breaches, in particular availability, confidentiality, and integrity breaches, in particular,
if an adversary has control over the values (e.g., by entering them if an adversary has control over the values (e.g., by entering them
into a Web form). The resulting class of attacks, _injections_ into a web form). The resulting class of attacks, _injections_
(e.g., SQL injections), is consistently found among the top causes of (e.g., SQL injections), is consistently found among the top causes of
application security vulnerabilities and requires particular application security vulnerabilities and requires particular
attention. attention.
4.3. Attacks on Security Mechanisms that Employ JSONPath 4.3. Attacks on Security Mechanisms That Employ JSONPath
Where JSONPath is used as a part of a security mechanism, attackers Where JSONPath is used as a part of a security mechanism, attackers
can attempt to provoke unexpected or unpredictable behavior, or take can attempt to provoke unexpected or unpredictable behavior or take
advantage of differences in behavior between JSONPath advantage of differences in behavior between JSONPath
implementations. implementations.
Unexpected or unpredictable behavior can arise from a query argument Unexpected or unpredictable behavior can arise from a query argument
with certain constructs described as unpredictable by [RFC8259]. with certain constructs described as unpredictable by [RFC8259].
Predictable behavior can be expected, except in relation to the Predictable behavior can be expected, except in relation to the
ordering of objects, for any query argument conforming with ordering of objects, for any query argument conforming with
[RFC7493]. [RFC7493].
Other attacks can target the behavior of underlying technologies such Other attacks can target the behavior of underlying technologies,
as UTF-8 (see Section 10 of [RFC3629]) and the Unicode character set. such as UTF-8 (see Section 10 of [RFC3629]) and the Unicode character
set.
5. References 5. References
5.1. Normative References 5.1. Normative References
[BCP26] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC0020] Cerf, V., "ASCII format for network interchange", STD 80,
Writing an IANA Considerations Section in RFCs", BCP 26, RFC 20, DOI 10.17487/RFC0020, October 1969,
RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc20>.
<https://www.rfc-editor.org/rfc/rfc8126>.
[I-D.draft-ietf-jsonpath-iregexp]
Bormann, C. and T. Bray, "I-Regexp: An Interoperable
Regexp Format", Work in Progress, Internet-Draft, draft-
ietf-jsonpath-iregexp-08, 29 June 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-
jsonpath-iregexp-08>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/rfc/rfc3629>. 2003, <https://www.rfc-editor.org/info/rfc3629>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008, DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/rfc/rfc5234>. <https://www.rfc-editor.org/info/rfc5234>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13, Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013, RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/rfc/rfc6838>. <https://www.rfc-editor.org/info/rfc6838>.
[RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493, [RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
DOI 10.17487/RFC7493, March 2015, DOI 10.17487/RFC7493, March 2015,
<https://www.rfc-editor.org/rfc/rfc7493>. <https://www.rfc-editor.org/info/rfc7493>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259, Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017, DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/rfc/rfc8259>. <https://www.rfc-editor.org/info/rfc8259>.
[STD80] Cerf, V., "ASCII format for network interchange", STD 80, [RFC9485] Bormann, C. and T. Bray, "I-Regexp: An Interoperable
RFC 20, DOI 10.17487/RFC0020, October 1969, Regular Expression Format", RFC 9485,
<https://www.rfc-editor.org/rfc/rfc20>. DOI 10.17487/RFC9485, October 2023,
<https://www.rfc-editor.org/info/rfc9485>.
[UNICODE] The Unicode Consortium, "The Unicode® Standard: Version [UNICODE] The Unicode Consortium, "The Unicode® Standard",
14.0 - Core Specification", September 2021, <https://www.unicode.org/versions/latest/>. At the time
<https://www.unicode.org/versions/Unicode14.0.0/ of writing,
UnicodeStandard-14.0.pdf>. <https://www.unicode.org/versions/Unicode15.0.0/
UnicodeStandard-15.0.pdf>.
5.2. Informative References 5.2. Informative References
[BOOLEAN-LAWS] [BOOLEAN-LAWS]
"Boolean algebra laws", n.d., "Boolean algebra: Laws", December 2023,
<https://en.wikipedia.org/wiki/Boolean_algebra#Laws>. <https://en.wikipedia.org/w/
index.php?title=Boolean_algebra&oldid=1191386550#Laws>.
[COMPARISON] [COMPARISON]
Burgmer, C., "JSONPath Comparison", n.d., Burgmer, C., "JSONPath Comparison",
<https://cburgmer.github.io/json-path-comparison/>. <https://cburgmer.github.io/json-path-comparison/>.
[E4X] ISO, "Information technology — ECMAScript for XML (E4X) [E4X] ISO, "Information technology - ECMAScript for XML (E4X)
specification", ISO/IEC 22537:2006 , 2006. specification", Withdrawn, ISO/IEC 22537:2006, February
2006, <https://www.iso.org/standard/41002.html>. An
equivalent specification, also withdrawn, is available
from <https://ecma-international.org/publications-and-
standards/standards/ecma-357>.
[ECMA-262] Ecma International, "ECMAScript Language Specification, [ECMA-262] ECMA International, "ECMAScript Language Specification",
Standard ECMA-262, Third Edition", December 1999, Standard ECMA-262, Third Edition, December 1999,
<https://www.ecma-international.org/wp-content/uploads/ <https://www.ecma-international.org/wp-content/uploads/
ECMA-262_3rd_edition_december_1999.pdf>. ECMA-262_3rd_edition_december_1999.pdf>.
[JSONPath-orig] [JSONPath-orig]
Gössner, S., "JSONPath — XPath for JSON", 21 February Gössner, S., "JSONPath - XPath for JSON", February 2007,
2007, <https://goessner.net/articles/JsonPath/>. <https://goessner.net/articles/JsonPath/>.
[RFC6901] Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed., [RFC6901] Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed.,
"JavaScript Object Notation (JSON) Pointer", RFC 6901, "JavaScript Object Notation (JSON) Pointer", RFC 6901,
DOI 10.17487/RFC6901, April 2013, DOI 10.17487/RFC6901, April 2013,
<https://www.rfc-editor.org/rfc/rfc6901>. <https://www.rfc-editor.org/info/rfc6901>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object [RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949, Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020, DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>. <https://www.rfc-editor.org/info/rfc8949>.
[SLICE] "Slice notation", n.d., [SLICE] "Slice notation", commit 82f95b4, July 2022,
<https://github.com/tc39/proposal-slice-notation>. <https://github.com/tc39/proposal-slice-notation>.
[XPath] Berglund, A., Ed., Chamberlin, D., Ed., Simeon, J., Ed., [XPath] Berglund, A., Ed., Chamberlin, D., Ed., Simeon, J., Ed.,
Robie, J., Ed., Fernandez, M., Ed., Kay, M., Ed., and S. Robie, J., Ed., Fernandez, M., Ed., Kay, M., Ed., and S.
Boag, Ed., "XML Path Language (XPath) 2.0 (Second Boag, Ed., "XML Path Language (XPath) 2.0 (Second
Edition)", W3C REC REC-xpath20-20101214, W3C REC- Edition)", W3C REC-xpath20-20101214, 14 December 2010,
xpath20-20101214, 14 December 2010,
<https://www.w3.org/TR/2010/REC-xpath20-20101214/>. <https://www.w3.org/TR/2010/REC-xpath20-20101214/>.
Appendix A. Collected ABNF grammars Appendix A. Collected ABNF Grammars
This appendix collects the ABNF grammar from the ABNF passages used This appendix collects the ABNF grammar from the ABNF passages used
throughout the document. throughout the document.
Figure 2 contains the collected ABNF grammar that defines the syntax Figure 2 contains the collected ABNF grammar that defines the syntax
of a JSONPath query. of a JSONPath query.
jsonpath-query = root-identifier segments jsonpath-query = root-identifier segments
segments = *(S segment) segments = *(S segment)
B = %x20 / ; Space B = %x20 / ; Space
%x09 / ; Horizontal tab %x09 / ; Horizontal tab
%x0A / ; Line feed or New line %x0A / ; Line feed or New line
%x0D ; Carriage return %x0D ; Carriage return
S = *B ; optional blank space S = *B ; optional blank space
root-identifier = "$" root-identifier = "$"
selector = name-selector / selector = name-selector /
wildcard-selector / wildcard-selector /
slice-selector / slice-selector /
index-selector / index-selector /
filter-selector filter-selector
name-selector = string-literal name-selector = string-literal
string-literal = %x22 *double-quoted %x22 / ; "string" string-literal = %x22 *double-quoted %x22 / ; "string"
%x27 *single-quoted %x27 ; 'string' %x27 *single-quoted %x27 ; 'string'
double-quoted = unescaped / double-quoted = unescaped /
%x27 / ; ' %x27 / ; '
ESC %x22 / ; \" ESC %x22 / ; \"
ESC escapable ESC escapable
single-quoted = unescaped / single-quoted = unescaped /
%x22 / ; " %x22 / ; "
ESC %x27 / ; \' ESC %x27 / ; \'
ESC escapable ESC escapable
ESC = %x5C ; \ backslash ESC = %x5C ; \ backslash
unescaped = %x20-21 / ; see RFC 8259 unescaped = %x20-21 / ; see RFC 8259
; omit 0x22 " ; omit 0x22 "
%x23-26 / %x23-26 /
; omit 0x27 ' ; omit 0x27 '
%x28-5B / %x28-5B /
; omit 0x5C \ ; omit 0x5C \
%x5D-D7FF / ; skip surrogate code points %x5D-D7FF /
; skip surrogate code points
%xE000-10FFFF %xE000-10FFFF
escapable = %x62 / ; b BS backspace U+0008 escapable = %x62 / ; b BS backspace U+0008
%x66 / ; f FF form feed U+000C %x66 / ; f FF form feed U+000C
%x6E / ; n LF line feed U+000A %x6E / ; n LF line feed U+000A
%x72 / ; r CR carriage return U+000D %x72 / ; r CR carriage return U+000D
%x74 / ; t HT horizontal tab U+0009 %x74 / ; t HT horizontal tab U+0009
"/" / ; / slash (solidus) U+002F "/" / ; / slash (solidus) U+002F
"\" / ; \ backslash (reverse solidus) U+005C "\" / ; \ backslash (reverse solidus) U+005C
(%x75 hexchar) ; uXXXX U+XXXX (%x75 hexchar) ; uXXXX U+XXXX
hexchar = non-surrogate / hexchar = non-surrogate /
(high-surrogate "\" %x75 low-surrogate) (high-surrogate "\" %x75 low-surrogate)
non-surrogate = ((DIGIT / "A"/"B"/"C" / "E"/"F") 3HEXDIG) / non-surrogate = ((DIGIT / "A"/"B"/"C" / "E"/"F") 3HEXDIG) /
("D" %x30-37 2HEXDIG ) ("D" %x30-37 2HEXDIG )
high-surrogate = "D" ("8"/"9"/"A"/"B") 2HEXDIG high-surrogate = "D" ("8"/"9"/"A"/"B") 2HEXDIG
low-surrogate = "D" ("C"/"D"/"E"/"F") 2HEXDIG low-surrogate = "D" ("C"/"D"/"E"/"F") 2HEXDIG
HEXDIG = DIGIT / "A" / "B" / "C" / "D" / "E" / "F" HEXDIG = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
wildcard-selector = "*" wildcard-selector = "*"
index-selector = int ; decimal integer index-selector = int ; decimal integer
int = "0" / int = "0" /
(["-"] DIGIT1 *DIGIT) ; - optional (["-"] DIGIT1 *DIGIT) ; - optional
DIGIT1 = %x31-39 ; 1-9 non-zero digit DIGIT1 = %x31-39 ; 1-9 non-zero digit
skipping to change at page 64, line 21 skipping to change at line 2801
; binds more tightly than disjunction ; binds more tightly than disjunction
basic-expr = paren-expr / basic-expr = paren-expr /
comparison-expr / comparison-expr /
test-expr test-expr
paren-expr = [logical-not-op S] "(" S logical-expr S ")" paren-expr = [logical-not-op S] "(" S logical-expr S ")"
; parenthesized expression ; parenthesized expression
logical-not-op = "!" ; logical NOT operator logical-not-op = "!" ; logical NOT operator
test-expr = [logical-not-op S] test-expr = [logical-not-op S]
(filter-query / ; existence/non-existence (filter-query / ; existence/non-existence
function-expr) ; LogicalType or NodesType function-expr) ; LogicalType or NodesType
filter-query = rel-query / jsonpath-query filter-query = rel-query / jsonpath-query
rel-query = current-node-identifier segments rel-query = current-node-identifier segments
current-node-identifier = "@" current-node-identifier = "@"
comparison-expr = comparable S comparison-op S comparable comparison-expr = comparable S comparison-op S comparable
literal = number / string-literal / literal = number / string-literal /
true / false / null true / false / null
comparable = literal / comparable = literal /
singular-query / ; singular query value singular-query / ; singular query value
function-expr ; ValueType function-expr ; ValueType
comparison-op = "==" / "!=" / comparison-op = "==" / "!=" /
skipping to change at page 65, line 23 skipping to change at line 2851
child-segment = bracketed-selection / child-segment = bracketed-selection /
("." ("."
(wildcard-selector / (wildcard-selector /
member-name-shorthand)) member-name-shorthand))
bracketed-selection = "[" S selector *(S "," S selector) S "]" bracketed-selection = "[" S selector *(S "," S selector) S "]"
member-name-shorthand = name-first *name-char member-name-shorthand = name-first *name-char
name-first = ALPHA / name-first = ALPHA /
"_" / "_" /
%x80-D7FF / ; skip surrogate code points %x80-D7FF /
; skip surrogate code points
%xE000-10FFFF %xE000-10FFFF
name-char = DIGIT / name-first name-char = name-first / DIGIT
DIGIT = %x30-39 ; 0-9 DIGIT = %x30-39 ; 0-9
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
descendant-segment = ".." (bracketed-selection / descendant-segment = ".." (bracketed-selection /
wildcard-selector / wildcard-selector /
member-name-shorthand) member-name-shorthand)
Figure 2: Collected ABNF of JSONPath queries Figure 2: Collected ABNF of JSONPath Queries
Figure 3 contains the collected ABNF grammar that defines the syntax Figure 3 contains the collected ABNF grammar that defines the syntax
of a JSONPath Normalized Path, while also using the rules root- of a JSONPath Normalized Path while also using the rules root-
identifier, ESC, DIGIT, and DIGIT1 from Figure 2. identifier, ESC, DIGIT, and DIGIT1 from Figure 2.
normalized-path = root-identifier *(normal-index-segment) normalized-path = root-identifier *(normal-index-segment)
normal-index-segment = "[" normal-selector "]" normal-index-segment = "[" normal-selector "]"
normal-selector = normal-name-selector / normal-index-selector normal-selector = normal-name-selector / normal-index-selector
normal-name-selector = %x27 *normal-single-quoted %x27 ; 'string' normal-name-selector = %x27 *normal-single-quoted %x27 ; 'string'
normal-single-quoted = normal-unescaped / normal-single-quoted = normal-unescaped /
ESC normal-escapable ESC normal-escapable
normal-unescaped = ; omit %x0-1F control codes normal-unescaped = ; omit %x0-1F control codes
%x20-26 / %x20-26 /
; omit 0x27 ' ; omit 0x27 '
%x28-5B / %x28-5B /
; omit 0x5C \ ; omit 0x5C \
%x5D-D7FF / ; skip surrogate code points %x5D-D7FF /
; skip surrogate code points
%xE000-10FFFF %xE000-10FFFF
normal-escapable = %x62 / ; b BS backspace U+0008 normal-escapable = %x62 / ; b BS backspace U+0008
%x66 / ; f FF form feed U+000C %x66 / ; f FF form feed U+000C
%x6E / ; n LF line feed U+000A %x6E / ; n LF line feed U+000A
%x72 / ; r CR carriage return U+000D %x72 / ; r CR carriage return U+000D
%x74 / ; t HT horizontal tab U+0009 %x74 / ; t HT horizontal tab U+0009
"'" / ; ' apostrophe U+0027 "'" / ; ' apostrophe U+0027
"\" / ; \ backslash (reverse solidus) U+005C "\" / ; \ backslash (reverse solidus) U+005C
(%x75 normal-hexchar) (%x75 normal-hexchar)
; certain values u00xx U+00XX ; certain values u00xx U+00XX
normal-hexchar = "0" "0" normal-hexchar = "0" "0"
( (
("0" %x30-37) / ; "00"-"07" ("0" %x30-37) / ; "00"-"07"
; omit U+0008-U+000A BS HT LF ; omit U+0008-U+000A BS HT LF
("0" %x62) / ; "0b" ("0" %x62) / ; "0b"
; omit U+000C-U+000D FF CR ; omit U+000C-U+000D FF CR
("0" %x65-66) / ; "0e"-"0f" ("0" %x65-66) / ; "0e"-"0f"
("1" normal-HEXDIG) ("1" normal-HEXDIG)
) )
normal-HEXDIG = DIGIT / %x61-66 ; "0"-"9", "a"-"f" normal-HEXDIG = DIGIT / %x61-66 ; "0"-"9", "a"-"f"
normal-index-selector = "0" / (DIGIT1 *DIGIT) normal-index-selector = "0" / (DIGIT1 *DIGIT)
; non-negative decimal integer ; non-negative decimal integer
Figure 3: Collected ABNF of JSONPath Normalized Paths Figure 3: Collected ABNF of JSONPath Normalized Paths
Appendix B. Inspired by XPath Appendix B. Inspired by XPath
This appendix is informative. This appendix is informative.
At the time JSONPath was invented, XML was noted for the availability At the time JSONPath was invented, XML was noted for the availability
of powerful tools to analyze, transform and selectively extract data of powerful tools to analyze, transform, and selectively extract data
from XML documents. [XPath] is one of these tools. from XML documents. [XPath] is one of these tools.
In 2007, the need for something solving the same class of problems In 2007, the need for something solving the same class of problems
for the emerging JSON community became apparent, specifically for: for the emerging JSON community became apparent, specifically for:
* Finding data interactively and extracting them out of [RFC8259] * finding data interactively and extracting them out of JSON values
JSON values without special scripting. [RFC8259] without special scripting and
* Specifying the relevant parts of the JSON data in a request by a * specifying the relevant parts of the JSON data in a request by a
client, so the server can reduce the amount of data in its client, so the server can reduce the amount of data in its
response, minimizing bandwidth usage. response, minimizing bandwidth usage.
(Note: XPath has evolved since 2007, and recent versions even (Note: XPath has evolved since 2007, and recent versions even
nominally support operating inside JSON values. This appendix only nominally support operating inside JSON values. This appendix only
discusses the more widely used version of XPath that was available in discusses the more widely used version of XPath that was available in
2007.) 2007.)
JSONPath picks up the overall feeling of XPath, but maps the concepts JSONPath picks up the overall feeling of XPath but maps the concepts
to syntax (and partially semantics) that would be familiar to someone to syntax (and partially semantics) that would be familiar to someone
using JSON in a dynamic language. using JSON in a dynamic language.
E.g., in popular dynamic programming languages such as JavaScript, For example, in popular dynamic programming languages such as
Python and PHP, the semantics of the XPath expression JavaScript, Python, and PHP, the semantics of the XPath expression:
/store/book[1]/title /store/book[1]/title
can be realized in the expression can be realized in the expression:
x.store.book[0].title x.store.book[0].title
or, in bracket notation, or in bracket notation:
x['store']['book'][0]['title'] x['store']['book'][0]['title']
with the variable x holding the query argument. with the variable x holding the query argument.
The JSONPath language was designed to: The JSONPath language was designed to:
* be naturally based on those language characteristics; * be naturally based on those language characteristics,
* cover only the most essential parts of XPath 1.0; * cover only the most essential parts of XPath 1.0,
* be lightweight in code size and memory consumption; * be lightweight in code size and memory consumption, and
* be runtime efficient. * be runtime efficient.
B.1. JSONPath and XPath B.1. JSONPath and XPath
JSONPath expressions apply to JSON values in the same way as XPath JSONPath expressions apply to JSON values in the same way as XPath
expressions are used in combination with an XML document. JSONPath expressions are used in combination with an XML document. JSONPath
uses $ to refer to the root node of the query argument, similar to uses $ to refer to the root node of the query argument, similar to
XPath's / at the front. XPath's / at the front.
JSONPath expressions move further down the hierarchy using _dot JSONPath expressions move further down the hierarchy using _dot
notation_ ($.store.book[0].title) or the _bracket notation_ notation_ ($.store.book[0].title) or the _bracket notation_
($['store']['book'][0]['title']), a lightweight/limited, and a more ($['store']['book'][0]['title']); both replace XPath's / within query
heavyweight syntax replacing XPath's / within query expressions. expressions, where _dot notation_ serves as a lightweight but limited
syntax while _bracket notation_ is a heavyweight but more general
syntax.
Both JSONPath and XPath use * for a wildcard. The descendant Both JSONPath and XPath use * for a wildcard. JSONPath's descendant
operators, starting with .., borrowed from [E4X], are similar to segment notation, starting with .., borrowed from [E4X], is similar
XPath's //. The array slicing construct [start:end:step] is unique to to XPath's //. The array slicing construct [start:end:step] is unique
JSONPath, inspired by [SLICE] from ECMASCRIPT 4. to JSONPath, inspired by [SLICE] from ECMASCRIPT 4.
Filter expressions are supported via the syntax ?<logical-expr> as in Filter expressions are supported via the syntax ?<logical-expr> as
in:
$.store.book[?@.price < 10].title $.store.book[?@.price < 10].title
Table 20 extends Table 1 by providing a comparison with similar XPath Table 20 extends Table 1 by providing a comparison with similar XPath
concepts. concepts.
+==========+==================+===================================+ +==========+==================+===================================+
| XPath | JSONPath | Description | | XPath | JSONPath | Description |
+==========+==================+===================================+ +==========+==================+===================================+
| / | $ | the root XML element | | / | $ | the root XML element |
skipping to change at page 69, line 47 skipping to change at line 3028
| | | from ES4 | | | | from ES4 |
+----------+------------------+-----------------------------------+ +----------+------------------+-----------------------------------+
| [] | ? | applies a filter (script) | | [] | ? | applies a filter (script) |
| | | expression | | | | expression |
+----------+------------------+-----------------------------------+ +----------+------------------+-----------------------------------+
| seamless | n/a | expression engine | | seamless | n/a | expression engine |
+----------+------------------+-----------------------------------+ +----------+------------------+-----------------------------------+
| () | n/a | grouping | | () | n/a | grouping |
+----------+------------------+-----------------------------------+ +----------+------------------+-----------------------------------+
Table 20: XPath syntax compared to JSONPath Table 20: XPath Syntax Compared to JSONPath
For further illustration, Table 21 shows some XPath expressions and For further illustration, Table 21 shows some XPath expressions and
their JSONPath equivalents. their JSONPath equivalents.
+======================+========================+===================+ +=======================+========================+==================+
| XPath | JSONPath | Result | | XPath | JSONPath | Result |
+======================+========================+===================+ +=======================+========================+==================+
| /store/book/author | $.store.book[*].author | the authors of | | /store/book/author | $.store.book[*].author | the authors |
| | | all books in | | | | of all books |
| | | the store | | | | in the store |
+----------------------+------------------------+-------------------+ +-----------------------+------------------------+------------------+
| //author | $..author | all authors | | //author | $..author | all authors |
+----------------------+------------------------+-------------------+ +-----------------------+------------------------+------------------+
| /store/* | $.store.* | all things in | | /store/* | $.store.* | all things in |
| | | store, which | | | | store, which |
| | | are some books | | | | are some |
| | | and a red | | | | books and a |
| | | bicycle | | | | red bicycle |
+----------------------+------------------------+-------------------+ +-----------------------+------------------------+------------------+
| /store//price | $.store..price | the prices of | | /store//price | $.store..price | the prices of |
| | | everything in | | | | everything in |
| | | the store | | | | the store |
+----------------------+------------------------+-------------------+ +-----------------------+------------------------+------------------+
| //book[3] | $..book[2] | the third book | | //book[3] | $..book[2] | the third |
+----------------------+------------------------+-------------------+ | | | book |
| //book[last()] | $..book[-1] | the last book | +-----------------------+------------------------+------------------+
| | | in order | | //book[last()] | $..book[-1] | the last book |
+----------------------+------------------------+-------------------+ | | | in order |
| //book[position()<3] | $..book[0,1] | the first two | +-----------------------+------------------------+------------------+
| | $..book[:2] | books | | //book[position()<3] | $..book[0,1] | the first two |
+----------------------+------------------------+-------------------+ | | $..book[:2] | books |
| //book[isbn] | $..book[?@.isbn] | filter all | +-----------------------+------------------------+------------------+
| | | books with isbn | | //book[isbn] | $..book[?@.isbn] | filter all |
| | | number | | | | books with an |
+----------------------+------------------------+-------------------+ | | | ISBN number |
| //book[price<10] | $..book[?@.price<10] | filter all | +-----------------------+------------------------+------------------+
| | | books cheaper | | //book[price<10] | $..book[?@.price<10] | filter all |
| | | than 10 | | | | books cheaper |
+----------------------+------------------------+-------------------+ | | | than 10 |
| //* | $..* | all elements in | +-----------------------+------------------------+------------------+
| | | XML document; | | //* | $..* | all elements |
| | | all member | | | | in an XML |
| | | values and | | | | document; all |
| | | array elements | | | | member values |
| | | contained in | | | | and array |
| | | input value | | | | elements |
+----------------------+------------------------+-------------------+ | | | contained in |
| | | input value |
+-----------------------+------------------------+------------------+
Table 21: Example XPath expressions and their JSONPath equivalents Table 21: Example XPath Expressions and Their JSONPath Equivalents
XPath has a lot more functionality (location paths in unabbreviated XPath has a lot more functionality (location paths in unabbreviated
syntax, operators and functions) than listed in this comparison. syntax, operators, and functions) than listed in this comparison.
Moreover, there are significant differences in how the subscript Moreover, there are significant differences in how the subscript
operator works in XPath and JSONPath: operator works in XPath and JSONPath:
* Square brackets in XPath expressions always operate on the _node * Square brackets in XPath expressions always operate on the _node
set_ resulting from the previous path fragment. Indices always set_ resulting from the previous path fragment. Indices always
start at 1. start at 1.
* With JSONPath, square brackets operate on each of the nodes in the * With JSONPath, square brackets operate on each of the nodes in the
_nodelist_ resulting from the previous query segment. Array _nodelist_ resulting from the previous query segment. Array
indices always start at 0. indices always start at 0.
Appendix C. JSON Pointer Appendix C. JSON Pointer
This appendix is informative. This appendix is informative.
JSONPath is not intended as a replacement for, but as a more powerful In relation to JSON Pointer [RFC6901], JSONPath is not intended as a
companion to, JSON Pointer [RFC6901]. The purposes of the two replacement but as a more powerful companion. The purposes of the
standards are different. two standards are different.
JSON Pointer is for identifying a single value within a JSON value JSON Pointer is for identifying a single value within a JSON value
whose structure is known. whose structure is known.
JSONPath can identify a single value within a JSON value, for example JSONPath can identify a single value within a JSON value, for
by using a Normalized Path. But JSONPath is also a query syntax that example, by using a Normalized Path. But JSONPath is also a query
can be used to search for and extract multiple values from JSON syntax that can be used to search for and extract multiple values
values whose structure is known only in a general way. from JSON values whose structure is known only in a general way.
A Normalized JSONPath can be converted into a JSON Pointer by A Normalized JSONPath can be converted into a JSON Pointer by
converting the syntax, without knowledge of any JSON value. The converting the syntax, without knowledge of any JSON value. The
inverse is not generally true: a numeric reference token (path inverse is not generally true, i.e., a numeric reference token (path
component) in a JSON Pointer may identify a member value of an object component) in a JSON Pointer may identify a member value of an object
or an element of an array. For conversion to a JSONPath query, or an element of an array. For conversion to a JSONPath query,
knowledge of the structure of the JSON value is needed to distinguish knowledge of the structure of the JSON value is needed to distinguish
these cases. these cases.
Acknowledgements Acknowledgements
This document is based on Stefan Gössner's original online article This document is based on Stefan Gössner's original online article
defining JSONPath [JSONPath-orig]. defining JSONPath [JSONPath-orig].
The books example was taken from http://coli.lili.uni- The books example was taken from course material that Bielefeld
bielefeld.de/~andreas/Seminare/sommer02/books.xml — a dead link now. University, Germany used in 2002.
This work is indebted to Christoph Burgmer for the superb JSONPath This work is indebted to Christoph Burgmer for the superb JSONPath
comparison project [COMPARISON] detailing the behavior of over forty comparison project [COMPARISON] that details the behavior of over
JSONPath implementations applied to numerous queries. forty JSONPath implementations applied to numerous queries.
Contributors Contributors
Marko Mikulicic Marko Mikulicic
InfluxData, Inc. InfluxData, Inc.
Pisa Pisa
Italy Italy
Email: mmikulicic@gmail.com Email: mmikulicic@gmail.com
Edward Surov Edward Surov
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