draft-reschke-http-jfv-07.txt		draft-reschke-http-jfv-08.txt
	Network Working Group J. Reschke		Network Working Group J. Reschke
	Internet-Draft greenbytes		Internet-Draft greenbytes
	Intended status: Standards Track October 24, 2017		Intended status: Standards Track February 2, 2018
	Expires: April 27, 2018		Expires: August 6, 2018
	A JSON Encoding for HTTP Header Field Values		A JSON Encoding for HTTP Header Field Values
	draft-reschke-http-jfv-07		draft-reschke-http-jfv-08
	Abstract		Abstract
	This document establishes a convention for use of JSON-encoded field		This document establishes a convention for use of JSON-encoded field
	values in HTTP header fields.		values in HTTP header fields.
	Editorial Note (To be removed by RFC Editor before publication)		Editorial Note (To be removed by RFC Editor before publication)
	Distribution of this document is unlimited. Although this is not a		Distribution of this document is unlimited. Although this is not a
	work item of the HTTPbis Working Group, comments should be sent to		work item of the HTTPbis Working Group, comments should be sent to
	the Hypertext Transfer Protocol (HTTP) mailing list at ietf-http-		the Hypertext Transfer Protocol (HTTP) mailing list at ietf-http-
	wg@w3.org [1], which may be joined by sending a message with subject		wg@w3.org [1], which may be joined by sending a message with subject
	"subscribe" to ietf-http-wg-request@w3.org [2].		"subscribe" to ietf-http-wg-request@w3.org [2].
	Discussions of the HTTPbis Working Group are archived at		Discussions of the HTTPbis Working Group are archived at
	<http://lists.w3.org/Archives/Public/ietf-http-wg/>.		<http://lists.w3.org/Archives/Public/ietf-http-wg/>.
	XML versions and latest edits for this document are available from		XML versions and latest edits for this document are available from
	<http://greenbytes.de/tech/webdav/#draft-reschke-http-jfv>.		<http://greenbytes.de/tech/webdav/#draft-reschke-http-jfv>.
	The changes in this draft are summarized in Appendix E.10.		The changes in this draft are summarized in Appendix E.11.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on April 27, 2018.		This Internet-Draft will expire on August 6, 2018.
	Copyright Notice		Copyright Notice
	Copyright (c) 2017 IETF Trust and the persons identified as the		Copyright (c) 2018 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	skipping to change at page 3, line 12 ¶		skipping to change at page 3, line 12 ¶
	E.1. Since draft-reschke-http-jfv-00 . . . . . . . . . . . . . 15		E.1. Since draft-reschke-http-jfv-00 . . . . . . . . . . . . . 15
	E.2. Since draft-reschke-http-jfv-01 . . . . . . . . . . . . . 15		E.2. Since draft-reschke-http-jfv-01 . . . . . . . . . . . . . 15
	E.3. Since draft-reschke-http-jfv-02 . . . . . . . . . . . . . 15		E.3. Since draft-reschke-http-jfv-02 . . . . . . . . . . . . . 15
	E.4. Since draft-reschke-http-jfv-03 . . . . . . . . . . . . . 15		E.4. Since draft-reschke-http-jfv-03 . . . . . . . . . . . . . 15
	E.5. Since draft-reschke-http-jfv-04 . . . . . . . . . . . . . 15		E.5. Since draft-reschke-http-jfv-04 . . . . . . . . . . . . . 15
	E.6. Since draft-ietf-httpbis-jfv-00 . . . . . . . . . . . . . 15		E.6. Since draft-ietf-httpbis-jfv-00 . . . . . . . . . . . . . 15
	E.7. Since draft-ietf-httpbis-jfv-01 . . . . . . . . . . . . . 15		E.7. Since draft-ietf-httpbis-jfv-01 . . . . . . . . . . . . . 15
	E.8. Since draft-ietf-httpbis-jfv-02 . . . . . . . . . . . . . 16		E.8. Since draft-ietf-httpbis-jfv-02 . . . . . . . . . . . . . 16
	E.9. Since draft-reschke-http-jfv-05 . . . . . . . . . . . . . 16		E.9. Since draft-reschke-http-jfv-05 . . . . . . . . . . . . . 16
	E.10. Since draft-reschke-http-jfv-06 . . . . . . . . . . . . . 16		E.10. Since draft-reschke-http-jfv-06 . . . . . . . . . . . . . 16
			E.11. Since draft-reschke-http-jfv-07 . . . . . . . . . . . . . 16
	Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 16		Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 16
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16
	1. Introduction		1. Introduction
	Defining syntax for new HTTP header fields ([RFC7230], Section 3.2)		Defining syntax for new HTTP header fields ([RFC7230], Section 3.2)
	is non-trivial. Among the commonly encountered problems are:		is non-trivial. Among the commonly encountered problems are:
	o There is no common syntax for complex field values. Several well-		o There is no common syntax for complex field values. Several well-
	known header fields do use a similarly looking syntax, but it is		known header fields do use a similarly looking syntax, but it is
	skipping to change at page 3, line 42 ¶		skipping to change at page 3, line 43 ¶
	encoding scheme is used. Furthermore, APIs usually assume a		encoding scheme is used. Furthermore, APIs usually assume a
	default encoding scheme in order to map from octet sequences to		default encoding scheme in order to map from octet sequences to
	strings (for instance, [XMLHttpRequest] uses the IDL type		strings (for instance, [XMLHttpRequest] uses the IDL type
	"ByteString", effectively resulting in the ISO-8859-1 character		"ByteString", effectively resulting in the ISO-8859-1 character
	encoding scheme [ISO-8859-1] being used).		encoding scheme [ISO-8859-1] being used).
	(See Section 8.3.1 of [RFC7231] for a summary of considerations for		(See Section 8.3.1 of [RFC7231] for a summary of considerations for
	new header fields.)		new header fields.)
	This specification addresses the issues listed above by defining both		This specification addresses the issues listed above by defining both
	a generic JSON-based ([RFC7159]) data model and a concrete wire		a generic JSON-based ([RFC8259]) data model and a concrete wire
	format that can be used in definitions of new header fields, where		format that can be used in definitions of new header fields, where
	the goals were:		the goals were:
	o to be compatible with header field recombination when fields occur		o to be compatible with header field recombination when fields occur
	multiple times in a single message (Section 3.2.2 of [RFC7230]),		multiple times in a single message (Section 3.2.2 of [RFC7230]),
	and		and
	o not to use any problematic characters in the field value (non-		o not to use any problematic characters in the field value (non-
	ASCII characters and certain whitespace characters).		ASCII characters and certain whitespace characters).
	skipping to change at page 4, line 17 ¶		skipping to change at page 4, line 20 ¶
	identify and formalize common field structures in existing header		identify and formalize common field structures in existing header
	fields; the syntax defined over there would usually lead to a more		fields; the syntax defined over there would usually lead to a more
	compact notation.		compact notation.
	2. Data Model and Format		2. Data Model and Format
	In HTTP, header fields with the same field name can occur multiple		In HTTP, header fields with the same field name can occur multiple
	times within a single message (Section 3.2.2 of [RFC7230]). When		times within a single message (Section 3.2.2 of [RFC7230]). When
	this happens, recipients are allowed to combine the field values		this happens, recipients are allowed to combine the field values
	using commas as delimiter. This rule matches nicely JSON's array		using commas as delimiter. This rule matches nicely JSON's array
	format (Section 5 of [RFC7159]). Thus, the basic data model used		format (Section 5 of [RFC8259]). Thus, the basic data model used
	here is the JSON array.		here is the JSON array.
	Header field definitions that need only a single value can restrict		Header field definitions that need only a single value can restrict
	themselves to arrays of length 1, and are encouraged to define error		themselves to arrays of length 1, and are encouraged to define error
	handling in case more values are received (such as "first wins",		handling in case more values are received (such as "first wins",
	"last wins", or "abort with fatal error message").		"last wins", or "abort with fatal error message").
	JSON arrays are mapped to field values by creating a sequence of		JSON arrays are mapped to field values by creating a sequence of
	serialized member elements, separated by commas and optionally		serialized member elements, separated by commas and optionally
	whitespace. This is equivalent to using the full JSON array format,		whitespace. This is equivalent to using the full JSON array format,
	skipping to change at page 4, line 43 ¶		skipping to change at page 4, line 46 ¶
	CR = %x0D ; carriage return		CR = %x0D ; carriage return
	HTAB = %x09 ; horizontal tab		HTAB = %x09 ; horizontal tab
	LF = %x0A ; line feed		LF = %x0A ; line feed
	SP = %x20 ; space		SP = %x20 ; space
	VCHAR = %x21-7E ; visible (printing) characters		VCHAR = %x21-7E ; visible (printing) characters
	Characters in JSON strings that are not allowed or discouraged in		Characters in JSON strings that are not allowed or discouraged in
	HTTP header field values -- that is, not in the "VCHAR" definition --		HTTP header field values -- that is, not in the "VCHAR" definition --
	need to be represented using JSON's "backslash" escaping mechanism		need to be represented using JSON's "backslash" escaping mechanism
	([RFC7159], Section 7).		([RFC8259], Section 7).
	The control characters CR, LF, and HTAB do not appear inside JSON		The control characters CR, LF, and HTAB do not appear inside JSON
	strings, but can be used outside (line breaks, indentation etc.).		strings, but can be used outside (line breaks, indentation etc.).
	These characters need to be either stripped or replaced by space		These characters need to be either stripped or replaced by space
	characters (ABNF "SP").		characters (ABNF "SP").
	Formally, using the HTTP specification's ABNF extensions defined in		Formally, using the HTTP specification's ABNF extensions defined in
	Section 7 of [RFC7230]:		Section 7 of [RFC7230]:
	json-field-value = #json-field-item		json-field-value = #json-field-item
	json-field-item = JSON-Text		json-field-item = JSON-Text
	; see [RFC7159], Section 2,		; see [RFC8259], Section 2,
	; post-processed so that only VCHAR characters		; post-processed so that only VCHAR characters
	; are used		; are used
	3. Sender Requirements		3. Sender Requirements
	To map a JSON array to an HTTP header field value, process each array		To map a JSON array to an HTTP header field value, process each array
	element separately by:		element separately by:
	1. generating the JSON representation,		1. generating the JSON representation,
	2. stripping all JSON control characters (CR, HTAB, LF), or		2. stripping all JSON control characters (CR, HTAB, LF), or
	replacing them by space ("SP") characters,		replacing them by space ("SP") characters,
	3. replacing all remaining non-VSPACE characters by the equivalent		3. replacing all remaining non-VSPACE characters by the equivalent
	backslash-escape sequence ([RFC7159], Section 7).		backslash-escape sequence ([RFC8259], Section 7).
	The resulting list of strings is transformed into an HTTP field value		The resulting list of strings is transformed into an HTTP field value
	by combining them using comma (%x2C) plus optional SP as delimiter,		by combining them using comma (%x2C) plus optional SP as delimiter,
	and encoding the resulting string into an octet sequence using the		and encoding the resulting string into an octet sequence using the
	US-ASCII character encoding scheme ([RFC0020]).		US-ASCII character encoding scheme ([RFC0020]).
	4. Recipient Requirements		4. Recipient Requirements
	To map a set of HTTP header field instances to a JSON array:		To map a set of HTTP header field instances to a JSON array:
	skipping to change at page 5, line 49 ¶		skipping to change at page 6, line 4 ¶
	3. run the resulting octet sequence through a JSON parser.		3. run the resulting octet sequence through a JSON parser.
	The result of the parsing operation is either an error (in which case		The result of the parsing operation is either an error (in which case
	the header field values needs to be considered invalid), or a JSON		the header field values needs to be considered invalid), or a JSON
	array.		array.
	5. Using this Format in Header Field Definitions		5. Using this Format in Header Field Definitions
	Specifications defining new HTTP header fields need to take the		Specifications defining new HTTP header fields need to take the
	considerations listed in Section 8.3.1 of [RFC7231] into account.		considerations listed in Section 8.3.1 of [RFC7231] into account.
	Many of these will already be accounted for by using the format		Many of these will already be accounted for by using the format
	defined in this specification.		defined in this specification.
	Readers of HTTP-related specifications frequently expect an ABNF		Readers of HTTP-related specifications frequently expect an ABNF
	definition of the field value syntax. This is not really needed		definition of the field value syntax. This is not really needed
	here, as the actual syntax is JSON text, as defined in Section 2 of		here, as the actual syntax is JSON text, as defined in Section 2 of
	[RFC7159].		[RFC8259].
	A very simple way to use this JSON encoding thus is just to cite this		A very simple way to use this JSON encoding thus is just to cite this
	specification -- specifically the "json-field-value" ABNF production		specification -- specifically the "json-field-value" ABNF production
	defined in Section 2 -- and otherwise not to talk about the details		defined in Section 2 -- and otherwise not to talk about the details
	of the field syntax at all.		of the field syntax at all.
	An alternative approach is just to repeat the ABNF-related parts from		An alternative approach is just to repeat the ABNF-related parts from
	Section 2.		Section 2.
	This frees the specification from defining the concrete on-the-wire		This frees the specification from defining the concrete on-the-wire
	skipping to change at page 7, line 7 ¶		skipping to change at page 7, line 7 ¶
	characters, and thus by definition use a subset of UTF-8 (Section 2.1		characters, and thus by definition use a subset of UTF-8 (Section 2.1
	of [RFC7493]).		of [RFC7493]).
	7.2. Numbers		7.2. Numbers
	Be aware of the issues around number precision, as discussed in		Be aware of the issues around number precision, as discussed in
	Section 2.2 of [RFC7493].		Section 2.2 of [RFC7493].
	7.3. Object Constraints		7.3. Object Constraints
	As described in Section 4 of [RFC7159], JSON parser implementations		As described in Section 4 of [RFC8259], JSON parser implementations
	differ in the handling of duplicate object names. Therefore, senders		differ in the handling of duplicate object names. Therefore, senders
	MUST NOT use duplicate object names, and recipients SHOULD either		MUST NOT use duplicate object names, and recipients SHOULD either
	treat field values with duplicate names as invalid (consistent with		treat field values with duplicate names as invalid (consistent with
	[RFC7493], Section 2.3) or use the lexically last value (consistent		[RFC7493], Section 2.3) or use the lexically last value (consistent
	with [ECMA-262], Section 24.3.1.1).		with [ECMA-262], Section 24.3.1.1).
	Furthermore, ordering of object members is not significant and can		Furthermore, ordering of object members is not significant and can
	not be relied upon.		not be relied upon.
	8. Internationalization Considerations		8. Internationalization Considerations
	skipping to change at page 7, line 37 ¶		skipping to change at page 7, line 37 ¶
	internationalization problem.		internationalization problem.
	Future specifications of HTTP might change to allow non-ASCII		Future specifications of HTTP might change to allow non-ASCII
	characters natively. In that case, header fields using the syntax		characters natively. In that case, header fields using the syntax
	defined by this specification would have a simple migration path (by		defined by this specification would have a simple migration path (by
	just stopping to require escaping of non-ASCII characters).		just stopping to require escaping of non-ASCII characters).
	9. Security Considerations		9. Security Considerations
	Using JSON-shaped field values is believed to not introduce any new		Using JSON-shaped field values is believed to not introduce any new
	threads beyond those described in Section 12 of [RFC7159], namely the		threads beyond those described in Section 12 of [RFC8259], namely the
	risk of recipients using the wrong tools to parse them.		risk of recipients using the wrong tools to parse them.
	Other than that, any syntax that makes extensions easy can be used to		Other than that, any syntax that makes extensions easy can be used to
	smuggle information through field values; however, this concern is		smuggle information through field values; however, this concern is
	shared with other widely used formats, such as those using parameters		shared with other widely used formats, such as those using parameters
	in the form of name/value pairs.		in the form of name/value pairs.
	10. References		10. References
	10.1. Normative References		10.1. Normative References
	[RFC0020] Cerf, V., "ASCII format for network interchange", STD 80,		[RFC0020] Cerf, V., "ASCII format for network interchange", STD 80,
	RFC 20, DOI 10.17487/RFC0020, October 1969,		RFC 20, DOI 10.17487/RFC0020, October 1969,
	<https://www.rfc-editor.org/info/rfc20>.		<https://www.rfc-editor.org/info/rfc20>.
	[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/info/rfc5234>.		<https://www.rfc-editor.org/info/rfc5234>.
	[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data
	Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
	2014, <https://www.rfc-editor.org/info/rfc7159>.
	[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer		[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
	Protocol (HTTP/1.1): Message Syntax and Routing",		Protocol (HTTP/1.1): Message Syntax and Routing",
	RFC 7230, DOI 10.17487/RFC7230, June 2014,		RFC 7230, DOI 10.17487/RFC7230, June 2014,
	<https://www.rfc-editor.org/info/rfc7230>.		<https://www.rfc-editor.org/info/rfc7230>.
	[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer		[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
	Protocol (HTTP/1.1): Semantics and Content", RFC 7231,		Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
	DOI 10.17487/RFC7231, June 2014,		DOI 10.17487/RFC7231, June 2014,
	<https://www.rfc-editor.org/info/rfc7231>.		<https://www.rfc-editor.org/info/rfc7231>.
	[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/info/rfc7493>.		<https://www.rfc-editor.org/info/rfc7493>.
			[RFC8259] Bray, T., "The JavaScript Object Notation (JSON) Data
			Interchange Format", STD 90, RFC 8259,
			DOI 10.17487/RFC8259, December 2017,
			<https://www.rfc-editor.org/info/rfc8259>.
	10.2. Informative References		10.2. Informative References
	[CLEARSITE]		[CLEARSITE]
	West, M., "Clear Site Data", W3C Working Draft WD-clear-		West, M., "Clear Site Data", W3C Working Draft WD-clear-
	site-data-20160720, July 2016,		site-data-20160720, July 2016,
	<http://www.w3.org/TR/2016/WD-clear-site-data-20160720/>.		<http://www.w3.org/TR/2016/WD-clear-site-data-20160720/>.
	Latest version available at <http://www.w3.org/TR/clear-		Latest version available at <http://www.w3.org/TR/clear-
	site-data/>.		site-data/>.
	[ECMA-262]		[ECMA-262]
	Ecma International, "ECMA-262 6th Edition, The ECMAScript		Ecma International, "ECMA-262 6th Edition, The ECMAScript
	2015 Language Specification", Standard ECMA-262, June		2015 Language Specification", Standard ECMA-262, June
	2015, <http://www.ecma-international.org/ecma-262/6.0/>.		2015, <http://www.ecma-international.org/ecma-262/6.0/>.
	[FEATUREPOL]		[FEATUREPOL]
	Clelland, I., "Clear Site Data", W3C Draft Community Group		Clelland, I., "Clear Site Data", W3C Draft Community Group
	Report , June 2017,		Report , June 2017,
	<https://wicg.github.io/feature-policy/>.		<https://wicg.github.io/feature-policy/>.
	[HSTRUCT] Kamp, P-H., "HTTP Header Common Structure", draft-ietf-		[HSTRUCT] Nottingham, M. and P-H. Kamp, "Structured Headers for
	httpbis-header-structure-01 (work in progress), April		HTTP", draft-ietf-httpbis-header-structure-03 (work in
	2017.		progress), February 2018.
	[ISO-8859-1]		[ISO-8859-1]
	International Organization for Standardization,		International Organization for Standardization,
	"Information technology -- 8-bit single-byte coded graphic		"Information technology -- 8-bit single-byte coded graphic
	character sets -- Part 1: Latin alphabet No. 1", ISO/		character sets -- Part 1: Latin alphabet No. 1", ISO/
	IEC 8859-1:1998, 1998.		IEC 8859-1:1998, 1998.
	[KEY] Fielding, R. and M. Nottingham, "The Key HTTP Response		[KEY] Fielding, R. and M. Nottingham, "The Key HTTP Response
	Header Field", draft-ietf-httpbis-key-01 (work in		Header Field", draft-ietf-httpbis-key-01 (work in
	progress), March 2016.		progress), March 2016.
	skipping to change at page 10, line 17 ¶		skipping to change at page 10, line 17 ¶
	This section shows how some of the existing HTTP header fields would		This section shows how some of the existing HTTP header fields would
	look like if they would use the format defined by this specification.		look like if they would use the format defined by this specification.
	A.1. Content-Length		A.1. Content-Length
	"Content-Length" is defined in Section 3.3.2 of [RFC7230], with the		"Content-Length" is defined in Section 3.3.2 of [RFC7230], with the
	field value's ABNF being:		field value's ABNF being:
	Content-Length = 1*DIGIT		Content-Length = 1*DIGIT
	So the field value is similar to a JSON number ([RFC7159],		So the field value is similar to a JSON number ([RFC8259],
	Section 6).		Section 6).
	Content-Length is restricted to a single field instance, as it		Content-Length is restricted to a single field instance, as it
	doesn't use the list production (as per Section 3.2.2 of [RFC7230]).		doesn't use the list production (as per Section 3.2.2 of [RFC7230]).
	However, in practice multiple instances do occur, and the definition		However, in practice multiple instances do occur, and the definition
	of the header field does indeed discuss how to handle these cases.		of the header field does indeed discuss how to handle these cases.
	If Content-Length was defined using the JSON format discussed here,		If Content-Length was defined using the JSON format discussed here,
	the ABNF would be something like:		the ABNF would be something like:
	Content-Length = #number		Content-Length = #number
	; number: [RFC7159], Section 6		; number: [RFC8259], Section 6
	...and the prose definition would:		...and the prose definition would:
	o restrict all numbers to be non-negative integers without		o restrict all numbers to be non-negative integers without
	fractions, and		fractions, and
	o require that the array of values is of length 1 (but allow the		o require that the array of values is of length 1 (but allow the
	case where the array is longer, but all members represent the same		case where the array is longer, but all members represent the same
	value)		value)
	skipping to change at page 14, line 21 ¶		skipping to change at page 14, line 21 ¶
	Defined in W3C Working Draft "Clear Site Data" (Section 2.1 of		Defined in W3C Working Draft "Clear Site Data" (Section 2.1 of
	[CLEARSITE]). Latest Editor's Draft at <https://w3c.github.io/		[CLEARSITE]). Latest Editor's Draft at <https://w3c.github.io/
	webappsec-clear-site-data/#header> replaces the use of JSON with a		webappsec-clear-site-data/#header> replaces the use of JSON with a
	custom syntax that happens to be somewhat compatible with an array of		custom syntax that happens to be somewhat compatible with an array of
	JSON strings (see <https://lists.w3.org/Archives/Public/ietf-http-		JSON strings (see <https://lists.w3.org/Archives/Public/ietf-http-
	wg/2017AprJun/0214.html> for feedback).		wg/2017AprJun/0214.html> for feedback).
	B.3. W3C Feature Policy Specification		B.3. W3C Feature Policy Specification
	Defined in W3C Draft Community Group Report "Feature Policy"		Originally defined in W3C Draft Community Group Report "Feature
	(Section 6.1 of [FEATUREPOL]). Previously relied on this document,		Policy" (Section 6.1 of [FEATUREPOL]), but now replaced with a custom
	now replicates the syntax into a custom ABNF defined in a separate		syntax (see <https://github.com/WICG/feature-policy/pull/83>).
	section (Section 5.1 of [FEATUREPOL]).
	Appendix C. Relation to HTTP 'Key' Header Field		Appendix C. Relation to HTTP 'Key' Header Field
	[KEY] aims to improve the cacheability of responses that vary based		[KEY] aims to improve the cacheability of responses that vary based
	on certain request header fields, addressing lack of granularity in		on certain request header fields, addressing lack of granularity in
	the existing "Vary" response header field ([RFC7231], Section 7.1.4).		the existing "Vary" response header field ([RFC7231], Section 7.1.4).
	If the JSON-based format described by this document gains popularity,		If the JSON-based format described by this document gains popularity,
	it might be useful to add a JSON-aware "Key Parameter" (see		it might be useful to add a JSON-aware "Key Parameter" (see
	Section 2.3 of [KEY]).		Section 2.3 of [KEY]).
	skipping to change at page 16, line 25 ¶		skipping to change at page 16, line 25 ¶
	Add a few lines on the relation to "Key".		Add a few lines on the relation to "Key".
	Summarize current use of the format.		Summarize current use of the format.
	E.10. Since draft-reschke-http-jfv-06		E.10. Since draft-reschke-http-jfv-06
	RFC 5987 is obsoleted by RFC 8187.		RFC 5987 is obsoleted by RFC 8187.
	Upcate CLEARSITE comment.		Upcate CLEARSITE comment.
			E.11. Since draft-reschke-http-jfv-07
			Update JSON and HSTRUCT references.
			FEATUREPOL doesn't use JSON syntax anymore.
	Acknowledgements		Acknowledgements
	Thanks go to the Hypertext Transfer Protocol Working Group		Thanks go to the Hypertext Transfer Protocol Working Group
	participants.		participants.
	Author's Address		Author's Address
	Julian F. Reschke		Julian F. Reschke
	greenbytes GmbH		greenbytes GmbH
	Hafenweg 16		Hafenweg 16
End of changes. 22 change blocks.
	27 lines changed or deleted		35 lines changed or added
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