rfc9165v3.txt		rfc9165.txt
	Internet Engineering Task Force (IETF) C. Bormann		Internet Engineering Task Force (IETF) C. Bormann
	Request for Comments: 9165 Universität Bremen TZI		Request for Comments: 9165 Universität Bremen TZI
	Category: Standards Track December 2021		Category: Standards Track December 2021
	ISSN: 2070-1721		ISSN: 2070-1721
	Additional Control Operators for Concise Data Definition Language (CDDL)		Additional Control Operators for the Concise Data Definition Language
			(CDDL)
	Abstract		Abstract
	The Concise Data Definition Language (CDDL), standardized in RFC		The Concise Data Definition Language (CDDL), standardized in RFC
	8610, provides "control operators" as its main language extension		8610, provides "control operators" as its main language extension
	point.		point.
	The present document defines a number of control operators that were		The present document defines a number of control operators that were
	not yet ready at the time RFC 8610 was completed: .plus, .cat, and		not yet ready at the time RFC 8610 was completed: .plus, .cat, and
	.det for the construction of constants; .abnf/.abnfb for including		.det for the construction of constants; .abnf/.abnfb for including
	skipping to change at line 162 ¶		skipping to change at line 163 ¶
	interval<X>		interval<X>
	interval<Y>		interval<Y>
	}		}
	Figure 1: An Example of Addition to a Base Value		Figure 1: An Example of Addition to a Base Value
	The example in Figure 1 contains the generic definition of a CDDL		The example in Figure 1 contains the generic definition of a CDDL
	group interval that gives a lower and upper bound and, optionally, a		group interval that gives a lower and upper bound and, optionally, a
	tolerance. The parameter BASE allows the non-conflicting use of a		tolerance. The parameter BASE allows the non-conflicting use of a
	multiple of these interval groups in one map by assigning different		multiple of these interval groups in one map by assigning different
	labels to the entries of the interval. rect combines two of these		labels to the entries of the interval. The rule rect combines two of
	interval groups into a map, one group for the X dimension (using 0,		these interval groups into a map, one group for the X dimension
	1, and 2 as labels) and one for the Y dimension (using 3, 4, and 5 as		(using 0, 1, and 2 as labels) and one for the Y dimension (using 3,
	labels).		4, and 5 as labels).
	2.2. String Concatenation		2.2. String Concatenation
	It is often useful to be able to compose string literals out of		It is often useful to be able to compose string literals out of
	component literals defined in different places in the specification.		component literals defined in different places in the specification.
	The .cat control identifies a string that is built from a		The .cat control identifies a string that is built from a
	concatenation of the target and the controller. The target and		concatenation of the target and the controller. The target and
	controller both MUST be strings. The result of the operation has the		controller both MUST be strings. The result of the operation has the
	same type as the target. The concatenation is performed on the bytes		same type as the target. The concatenation is performed on the bytes
	skipping to change at line 188 ¶		skipping to change at line 189 ¶
	c = "foo" .cat '		c = "foo" .cat '
	bar		bar
	baz		baz
	'		'
	; on a system where the newline is \n, is the same string as:		; on a system where the newline is \n, is the same string as:
	b = "foo\n bar\n baz\n"		b = "foo\n bar\n baz\n"
	Figure 2: An Example of Concatenation of Text and Byte Strings		Figure 2: An Example of Concatenation of Text and Byte Strings
	The example in Figure 2 builds a text string named a text string		The example in Figure 2 builds a text string named c from
	named c from concatenating the target text string "foo" and the		concatenating the target text string "foo" and the controller byte
	controller byte string entered in a text form byte string literal.		string entered in a text form byte string literal. (This particular
	(This particular idiom is useful when the text string contains		idiom is useful when the text string contains newlines, which, as
	newlines, which, as shown in the example for b, may be harder to read		shown in the example for b, may be harder to read when entered in the
	when entered in the format that the pure CDDL text string notation		format that the pure CDDL text string notation inherits from JSON.)
	inherits from JSON.)
	2.3. String Concatenation with Dedenting		2.3. String Concatenation with Dedenting
	Multi-line string literals for various applications, including		Multi-line string literals for various applications, including
	embedded ABNF (Section 3), need to be set flush left, at least		embedded ABNF (Section 3), need to be set flush left, at least
	partially. Often, having some indentation in the source code for the		partially. Often, having some indentation in the source code for the
	literal can promote readability, as in Figure 3.		literal can promote readability, as in Figure 3.
	oid = bytes .abnfb ("oid" .det cbor-tags-oid)		oid = bytes .abnfb ("oid" .det cbor-tags-oid)
	roid = bytes .abnfb ("roid" .det cbor-tags-oid)		roid = bytes .abnfb ("roid" .det cbor-tags-oid)
End of changes. 3 change blocks.
	12 lines changed or deleted		12 lines changed or added
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