draft-reschke-http-jfv-09.txt		draft-reschke-http-jfv-10.txt
	Network Working Group J. Reschke		Network Working Group J. F. Reschke
	Internet-Draft greenbytes		Internet-Draft greenbytes
	Intended status: Standards Track July 2, 2018		Intended status: Informational 14 October 2019
	Expires: January 3, 2019		Expires: 16 April 2020
	A JSON Encoding for HTTP Header Field Values		A JSON Encoding for HTTP Header Field Values
	draft-reschke-http-jfv-09		draft-reschke-http-jfv-10
	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
			This note is to be removed before publishing as an RFC.
	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 (mailto:ietf-http-wg@w3.org), which may be joined by
	"subscribe" to ietf-http-wg-request@w3.org [2].		sending a message with subject "subscribe" to ietf-http-wg-
			request@w3.org (mailto:ietf-http-wg-
			request@w3.org?subject=subscribe).
	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.12.		The changes in this draft are summarized in Appendix E.13.
	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 16 April 2020.
	This Internet-Draft will expire on January 3, 2019.
	Copyright Notice		Copyright Notice
	Copyright (c) 2018 IETF Trust and the persons identified as the		Copyright (c) 2019 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/
	(https://trustee.ietf.org/license-info) in effect on the date of		license-info) in effect on the date of publication of this document.
	publication of this document. Please review these documents		Please review these documents carefully, as they describe your rights
	carefully, as they describe your rights and restrictions with respect		and restrictions with respect to this document. Code Components
	to this document. Code Components extracted from this document must		extracted from this document must include Simplified BSD License text
	include Simplified BSD License text as described in Section 4.e of		as described in Section 4.e of the Trust Legal Provisions and are
	the Trust Legal Provisions and are provided without warranty as		provided without warranty as described in the Simplified BSD License.
	described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Data Model and Format . . . . . . . . . . . . . . . . . . . . 4		2. Data Model and Format . . . . . . . . . . . . . . . . . . . . 4
	3. Sender Requirements . . . . . . . . . . . . . . . . . . . . . 5		3. Sender Requirements . . . . . . . . . . . . . . . . . . . . . 5
	4. Recipient Requirements . . . . . . . . . . . . . . . . . . . 5		4. Recipient Requirements . . . . . . . . . . . . . . . . . . . 5
	5. Using this Format in Header Field Definitions . . . . . . . . 5		5. Using this Format in Header Field Definitions . . . . . . . . 5
	6. Deployment Considerations . . . . . . . . . . . . . . . . . . 6		6. Deployment Considerations . . . . . . . . . . . . . . . . . . 6
	7. Interoperability Considerations . . . . . . . . . . . . . . . 6		7. Interoperability Considerations . . . . . . . . . . . . . . . 6
	7.1. Encoding and Characters . . . . . . . . . . . . . . . . . 6		7.1. Encoding and Characters . . . . . . . . . . . . . . . . . 6
	7.2. Numbers . . . . . . . . . . . . . . . . . . . . . . . . . 6		7.2. Numbers . . . . . . . . . . . . . . . . . . . . . . . . . 6
	7.3. Object Constraints . . . . . . . . . . . . . . . . . . . 7		7.3. Object Constraints . . . . . . . . . . . . . . . . . . . 6
	8. Internationalization Considerations . . . . . . . . . . . . . 7		8. Internationalization Considerations . . . . . . . . . . . . . 7
	9. Security Considerations . . . . . . . . . . . . . . . . . . . 7		9. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7		10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	10.1. Normative References . . . . . . . . . . . . . . . . . . 7		10.1. Normative References . . . . . . . . . . . . . . . . . . 7
	10.2. Informative References . . . . . . . . . . . . . . . . . 8		10.2. Informative References . . . . . . . . . . . . . . . . . 8
	10.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 9		Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 9
	Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 10		A.1. Content-Length . . . . . . . . . . . . . . . . . . . . . 9
	A.1. Content-Length . . . . . . . . . . . . . . . . . . . . . 10
	A.2. Content-Disposition . . . . . . . . . . . . . . . . . . . 10		A.2. Content-Disposition . . . . . . . . . . . . . . . . . . . 10
	A.3. WWW-Authenticate . . . . . . . . . . . . . . . . . . . . 11		A.3. WWW-Authenticate . . . . . . . . . . . . . . . . . . . . 11
	A.4. Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 12		A.4. Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 12
	Appendix B. Use of JSON Field Value Encoding in the Wild . . . . 13		Appendix B. Use of JSON Field Value Encoding in the
	B.1. W3C Reporting API Specification . . . . . . . . . . . . . 14		Wild . . . . . . . . . . . . . . . . . . . . . . . . . . 13
	B.2. W3C Clear Site Data Specification . . . . . . . . . . . . 14		B.1. W3C Reporting API Specification . . . . . . . . . . . . . 13
	B.3. W3C Feature Policy Specification . . . . . . . . . . . . 14		B.2. W3C Clear Site Data Specification . . . . . . . . . . . . 13
			B.3. W3C Feature Policy Specification . . . . . . . . . . . . 13
	Appendix C. Relation to HTTP 'Key' Header Field . . . . . . . . 14		Appendix C. Relation to HTTP 'Key' Header Field . . . . . . . . 14
	Appendix D. Discussion . . . . . . . . . . . . . . . . . . . . . 14		Appendix D. Discussion . . . . . . . . . . . . . . . . . . . . . 14
	Appendix E. Change Log (to be removed by RFC Editor before		Appendix E. Change Log . . . . . . . . . . . . . . . . . . . . . 14
	publication) . . . . . . . . . . . . . . . . . . . . 14		E.1. Since draft-reschke-http-jfv-00 . . . . . . . . . . . . . 14
	E.1. Since draft-reschke-http-jfv-00 . . . . . . . . . . . . . 15		E.2. Since draft-reschke-http-jfv-01 . . . . . . . . . . . . . 14
	E.2. Since draft-reschke-http-jfv-01 . . . . . . . . . . . . . 15		E.3. Since draft-reschke-http-jfv-02 . . . . . . . . . . . . . 14
	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 . . . . . . . . . . . . . 15		E.8. Since draft-ietf-httpbis-jfv-02 . . . . . . . . . . . . . 15
	E.9. Since draft-reschke-http-jfv-05 . . . . . . . . . . . . . 16		E.9. Since draft-reschke-http-jfv-05 . . . . . . . . . . . . . 15
	E.10. Since draft-reschke-http-jfv-06 . . . . . . . . . . . . . 16		E.10. Since draft-reschke-http-jfv-06 . . . . . . . . . . . . . 15
	E.11. Since draft-reschke-http-jfv-07 . . . . . . . . . . . . . 16		E.11. Since draft-reschke-http-jfv-07 . . . . . . . . . . . . . 15
	E.12. Since draft-reschke-http-jfv-08 . . . . . . . . . . . . . 16		E.12. Since draft-reschke-http-jfv-08 . . . . . . . . . . . . . 16
			E.13. Since draft-reschke-http-jfv-09 . . . . . . . . . . . . . 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-		* 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
	hard to write generic parsing code that will both correctly handle		hard to write generic parsing code that will both correctly handle
	valid field values but also reject invalid ones.		valid field values but also reject invalid ones.
	o The HTTP message format allows header fields to repeat, so field		* The HTTP message format allows header fields to repeat, so field
	syntax needs to be designed in a way that these cases are either		syntax needs to be designed in a way that these cases are either
	meaningful, or can be unambiguously detected and rejected.		meaningful, or can be unambiguously detected and rejected.
	o HTTP/1.1 does not define a character encoding scheme ([RFC6365],		* HTTP/1.1 does not define a character encoding scheme ([RFC6365],
	Section 2), so header fields are either stuck with US-ASCII		Section 2), so header fields are either stuck with US-ASCII
	([RFC0020]), or need out-of-band information to decide what		([RFC0020]), or need out-of-band information to decide what
	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 ([RFC8259]) 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		* 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-		* not to use any problematic characters in the field value (non-
	ASCII characters and certain whitespace characters).		ASCII characters and certain whitespace characters).
	Note: [HSTRUCT], a work item of the IETF HTTP Working Group, is a		| *Note:*[HSTRUCT], a work item of the IETF HTTP Working Group,
	different attempt to address this set of problems -- it tries to		| is a different attempt to address this set of problems -- it
	identify and formalize common field structures in existing header		| tries to identify and formalize common field structures in
	fields; the syntax defined over there would usually lead to a more		| existing header fields; the syntax defined over there would
	compact notation.		| usually lead to a more 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 [RFC8259]). 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.
	skipping to change at page 4, line 37 ¶		skipping to change at page 4, line 37 ¶
	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,
	while leaving out the "begin-array" ('[') and "end-array" (']')		while leaving out the "begin-array" ('[') and "end-array" (']')
	delimiters.		delimiters.
	The ABNF character names and classes below are used (copied from		The ABNF character names and classes below are used (copied from
	[RFC5234], Appendix B.1):		[RFC5234], Appendix B.1):
	CR = %x0D ; carriage return		CR = %x0D ; carriage return HTAB = %x09 ; horizontal tab LF = %x0A ; line feed SP = %x20 ; space VCHAR = %x21-7E ; visible (printing) characters
	HTAB = %x09 ; horizontal tab
	LF = %x0A ; line feed
	SP = %x20 ; space
	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
	([RFC8259], 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 ; see [RFC8259], Section 2, ; post-processed so that only VCHAR characters ; are used
	json-field-item = JSON-Text
	; see [RFC8259], Section 2,
	; post-processed so that only VCHAR characters
	; 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,
	skipping to change at page 8, line 10 ¶		skipping to change at page 7, line 49 ¶
	[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>.
	[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer		[RFC7230] Fielding, R., Ed. and J. F. Reschke, Ed., "Hypertext
	Protocol (HTTP/1.1): Message Syntax and Routing",		Transfer 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. F. Reschke, Ed., "Hypertext
	Protocol (HTTP/1.1): Semantics and Content", RFC 7231,		Transfer Protocol (HTTP/1.1): Semantics and Content",
	DOI 10.17487/RFC7231, June 2014,		RFC 7231, 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., Ed., "The JavaScript Object Notation (JSON) Data		[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
	Interchange Format", RFC 8259, DOI 10.17487/RFC8259,		Interchange Format", RFC 8259, DOI 10.17487/RFC8259,
	December 2017, <https://www.rfc-editor.org/info/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-20171130, November 2017,		site-data-20171130, 30 November 2017,
	<https://www.w3.org/TR/2017/WD-clear-site-data-20171130/>.		<https://www.w3.org/TR/2017/WD-clear-site-data-20171130/>.
			Latest version available at https://www.w3.org/TR/clear-
			site-data/.
	Latest version available at <https://www.w3.org/TR/clear-		[ECMA-262] Ecma International, "ECMA-262 6th Edition, The ECMAScript
	site-data/>.
	[ECMA-262]
	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., "Feature Policy", W3C Draft Community Group		Clelland, I., "Feature Policy", W3C Draft Community Group
	Report , June 2018,		Report , 3 October 2019,
	<https://wicg.github.io/feature-policy/>.		<https://wicg.github.io/feature-policy/>.
	[HSTRUCT] Nottingham, M. and P-H. Kamp, "Structured Headers for		[HSTRUCT] Nottingham, M. and P-H. Kamp, "Structured Headers for
	HTTP", draft-ietf-httpbis-header-structure-07 (work in		HTTP", Internet-Draft, draft-ietf-httpbis-header-
	progress), July 2018.		structure-13, August 2019,
			<https://tools.ietf.org/html/draft-ietf-httpbis-header-
			structure-13>.
	[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", Internet-Draft, draft-ietf-httpbis-key-01,
	progress), March 2016.		March 2016,
			<https://tools.ietf.org/html/draft-ietf-httpbis-key-01>.
	[REPORTING]		[REPORTING]
	Grigorik, I. and M. West, "Reporting API 1", W3C Group		Creager, D., Grigorik, I., Meyer, P., and M. West,
	Note NOTE-reporting-1-20160607, June 2016,		"Reporting API", W3C Working Draft WD-reporting-
	<http://www.w3.org/TR/2016/NOTE-reporting-1-20160607/>.		1-20180925, 25 September 2018,
			<https://www.w3.org/TR/2018/WD-reporting-1-20180925/>.
	Latest version available at <http://www.w3.org/TR/		Latest version available at https://www.w3.org/TR/
	reporting-1/>.		reporting-1/.
	[RFC6266] Reschke, J., "Use of the Content-Disposition Header Field		[RFC6266] Reschke, J. F., "Use of the Content-Disposition Header
	in the Hypertext Transfer Protocol (HTTP)", RFC 6266,		Field in the Hypertext Transfer Protocol (HTTP)",
	DOI 10.17487/RFC6266, June 2011,		RFC 6266, DOI 10.17487/RFC6266, June 2011,
	<https://www.rfc-editor.org/info/rfc6266>.		<https://www.rfc-editor.org/info/rfc6266>.
	[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in		[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
	Internationalization in the IETF", BCP 166, RFC 6365,		Internationalization in the IETF", BCP 166, RFC 6365,
	DOI 10.17487/RFC6365, September 2011,		DOI 10.17487/RFC6365, September 2011,
	<https://www.rfc-editor.org/info/rfc6365>.		<https://www.rfc-editor.org/info/rfc6365>.
	[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer		[RFC7235] Fielding, R., Ed. and J. F. Reschke, Ed., "Hypertext
	Protocol (HTTP/1.1): Authentication", RFC 7235,		Transfer Protocol (HTTP/1.1): Authentication", RFC 7235,
	DOI 10.17487/RFC7235, June 2014,		DOI 10.17487/RFC7235, June 2014,
	<https://www.rfc-editor.org/info/rfc7235>.		<https://www.rfc-editor.org/info/rfc7235>.
	[RFC8187] Reschke, J., "Indicating Character Encoding and Language		[RFC8187] Reschke, J. F., "Indicating Character Encoding and
	for HTTP Header Field Parameters", RFC 8187,		Language for HTTP Header Field Parameters", RFC 8187,
	DOI 10.17487/RFC8187, September 2017,		DOI 10.17487/RFC8187, September 2017,
	<https://www.rfc-editor.org/info/rfc8187>.		<https://www.rfc-editor.org/info/rfc8187>.
	[XMLHttpRequest]		[XMLHttpRequest]
	WhatWG, "XMLHttpRequest", <https://xhr.spec.whatwg.org/>.		WhatWG, "XMLHttpRequest", October 2019,
			<https://xhr.spec.whatwg.org/>.
	10.3. URIs
	[1] mailto:ietf-http-wg@w3.org
	[2] mailto:ietf-http-wg-request@w3.org?subject=subscribe
	Appendix A. Examples		Appendix A. Examples
	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 ([RFC8259],		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: [RFC8259], 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		* 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		* 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)
	A.2. Content-Disposition		A.2. Content-Disposition
	Content-Disposition field values, defined in [RFC6266], consist of a		Content-Disposition field values, defined in [RFC6266], consist of a
	"disposition type" (a string), plus multiple parameters, of which at		"disposition type" (a string), plus multiple parameters, of which at
	least one ("filename") sometime needs to carry non-ASCII characters.		least one ("filename") sometime needs to carry non-ASCII characters.
	For instance, the first example in Section 5 of [RFC6266]:		For instance, the first example in Section 5 of [RFC6266]:
	skipping to change at page 11, line 22 ¶		skipping to change at page 11, line 7 ¶
	{ "Attachment": { "filename" : "example.html" } }		{ "Attachment": { "filename" : "example.html" } }
	The third example in Section 5 of [RFC6266] uses a filename parameter		The third example in Section 5 of [RFC6266] uses a filename parameter
	containing non-US-ASCII characters:		containing non-US-ASCII characters:
	attachment; filename*=UTF-8''%e2%82%ac%20rates		attachment; filename*=UTF-8''%e2%82%ac%20rates
	Note that in this case, the "filename*" parameter uses the encoding		Note that in this case, the "filename*" parameter uses the encoding
	defined in [RFC8187], representing a filename starting with the		defined in [RFC8187], representing a filename starting with the
	Unicode character U+20AC (EURO SIGN), followed by " rates". If the		Unicode character "€" (EURO SIGN, U+20AC), followed by " rates". If
	definition of Content-Disposition would have used the format proposed		the definition of Content-Disposition would have used the format
	here, the workaround involving the "parameter*" syntax would not have		proposed here, the workaround involving the "parameter*" syntax would
	been needed at all.		not have been needed at all.
	The JSON representation of this value could then be:		The JSON representation of this value could then be:
	{ "attachment": { "filename" : "\u20AC rates" } }		{ "attachment": { "filename" : "\u20AC rates" } }
	A.3. WWW-Authenticate		A.3. WWW-Authenticate
	The WWW-Authenticate header field value is defined in Section 4.1 of		The WWW-Authenticate header field value is defined in Section 4.1 of
	[RFC7235] as a list of "challenges":		[RFC7235] as a list of "challenges":
	skipping to change at page 12, line 32 ¶		skipping to change at page 12, line 17 ¶
	{ "Newauth" : { "realm": "apps", "type" : 1,		{ "Newauth" : { "realm": "apps", "type" : 1,
	"title": "Login to \"apps\"" }},		"title": "Login to \"apps\"" }},
	{ "Basic" : { "realm": "simple"}}		{ "Basic" : { "realm": "simple"}}
	A.4. Accept-Encoding		A.4. Accept-Encoding
	The Accept-Encoding header field value is defined in Section 5.3.4 of		The Accept-Encoding header field value is defined in Section 5.3.4 of
	[RFC7231] as a list of codings, each of which allowing a weight		[RFC7231] as a list of codings, each of which allowing a weight
	parameter 'q':		parameter 'q':
	Accept-Encoding = #( codings [ weight ] )		Accept-Encoding = #( codings [ weight ] ) codings = content-coding / "identity" / "*" weight = OWS ";" OWS "q=" qvalue qvalue = ( "0" [ "." 0*3DIGIT ] ) / ( "1" [ "." 0*3("0") ] )
	codings = content-coding / "identity" / "*"
	weight = OWS ";" OWS "q=" qvalue
	qvalue = ( "0" [ "." 0*3DIGIT ] )
	/ ( "1" [ "." 0*3("0") ] )
	An example for a complex header field value given in the definition		An example for a complex header field value given in the definition
	of the header field is:		of the header field is:
	gzip;q=1.0, identity; q=0.5, *;q=0		gzip;q=1.0, identity; q=0.5, *;q=0
	Due to the defaulting rules for the quality value ([RFC7231],		Due to the defaulting rules for the quality value ([RFC7231],
	Section 5.3.1), this could also be written as:		Section 5.3.1), this could also be written as:
	gzip, identity; q=0.5, *; q=0		gzip, identity; q=0.5, *; q=0
	skipping to change at page 13, line 49 ¶		skipping to change at page 13, line 28 ¶
	"gzip", "deflate"		"gzip", "deflate"
	which would be only a small overhead over the original format.		which would be only a small overhead over the original format.
	Appendix B. Use of JSON Field Value Encoding in the Wild		Appendix B. Use of JSON Field Value Encoding in the Wild
	Since work started on this document, various specifications have		Since work started on this document, various specifications have
	adopted this format. At least one of these moved away after the HTTP		adopted this format. At least one of these moved away after the HTTP
	Working Group decided to focus on [HSTRUCT] (see thread starting at		Working Group decided to focus on [HSTRUCT] (see thread starting at
	<https://lists.w3.org/Archives/Public/ietf-http-		https://lists.w3.org/Archives/Public/ietf-http-
	wg/2016OctDec/0505.html>).		wg/2016OctDec/0505.html).
	The sections below summarize the current usage of this format.		The sections below summarize the current usage of this format.
	B.1. W3C Reporting API Specification		B.1. W3C Reporting API Specification
	Defined in W3C Note "Reporting API 1" (Section 3.1 of [REPORTING]).		Defined in W3C Working Draft "Reporting API" (Section 3.1 of
	Still in use in latest editor copy as of June 2017.		[REPORTING]). Still in use in latest working draft dated September
			2018.
	B.2. W3C Clear Site Data Specification		B.2. W3C Clear Site Data Specification
	Used in earlier versions of "Clear Site Data". The current version		Used in earlier versions of "Clear Site Data". The current version
	replaces the use of JSON with a custom syntax that happens to be		replaces the use of JSON with a custom syntax that happens to be
	somewhat compatible with an array of JSON strings (see Section 3.1 of		somewhat compatible with an array of JSON strings (see Section 3.1 of
	[CLEARSITE] and <https://lists.w3.org/Archives/Public/ietf-http-		[CLEARSITE] and 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
	Originally defined in W3C Draft Community Group Report "Feature		Originally defined in W3C Draft Community Group Report "Feature
	Policy" ([FEATUREPOL]), but now replaced with a custom syntax (see		Policy" ([FEATUREPOL]), but now replaced with a custom syntax (see
	<https://github.com/WICG/feature-policy/pull/83>).		https://github.com/WICG/feature-policy/pull/83).
	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]).
	Appendix D. Discussion		Appendix D. Discussion
	This approach uses a default of "JSON array", using implicit array		This approach uses a default of "JSON array", using implicit array
	markers. An alternative would be a default of "JSON object". This		markers. An alternative would be a default of "JSON object". This
	would simplify the syntax for non-list-typed header fields, but all		would simplify the syntax for non-list-typed header fields, but all
	the benefits of having the same data model for both types of header		the benefits of having the same data model for both types of header
	fields would be gone. A hybrid approach might make sense, as long as		fields would be gone. A hybrid approach might make sense, as long as
	it doesn't require any heuristics on the recipient's side.		it doesn't require any heuristics on the recipient's side.
	Note: a concrete proposal was made by Kazuho Oku in		| *Note:* a concrete proposal was made by Kazuho Oku in
	<https://lists.w3.org/Archives/Public/ietf-http-		| https://lists.w3.org/Archives/Public/ietf-http-
	wg/2016JanMar/0155.html>.		| wg/2016JanMar/0155.html.
	[[CREF1: Use of generic libs vs compactness of field values..]]		// Use of generic libs vs compactness of field values..
			Appendix E. Change Log
			This section is to be removed before publishing as an RFC.
	Appendix E. Change Log (to be removed by RFC Editor before publication)
	E.1. Since draft-reschke-http-jfv-00		E.1. Since draft-reschke-http-jfv-00
	Editorial fixes + working on the TODOs.		Editorial fixes + working on the TODOs.
	E.2. Since draft-reschke-http-jfv-01		E.2. Since draft-reschke-http-jfv-01
	Mention slightly increased risk of smuggling information in header		Mention slightly increased risk of smuggling information in header
	field values.		field values.
	E.3. Since draft-reschke-http-jfv-02		E.3. Since draft-reschke-http-jfv-02
	skipping to change at page 15, line 29 ¶		skipping to change at page 15, line 12 ¶
	Expand I18N section.		Expand I18N section.
	E.4. Since draft-reschke-http-jfv-03		E.4. Since draft-reschke-http-jfv-03
	Mention relation to KEY header field.		Mention relation to KEY header field.
	E.5. Since draft-reschke-http-jfv-04		E.5. Since draft-reschke-http-jfv-04
	Between June and December 2016, this was a work item of the HTTP		Between June and December 2016, this was a work item of the HTTP
	working group (see <https://datatracker.ietf.org/doc/draft-ietf-		working group (see https://datatracker.ietf.org/doc/draft-ietf-
	httpbis-jfv/>). Work (if any) continues now on		httpbis-jfv/). Work (if any) continues now on
	<https://datatracker.ietf.org/doc/draft-reschke-http-jfv/>.		https://datatracker.ietf.org/doc/draft-reschke-http-jfv/.
	Changes made while this was a work item of the HTTP Working Group:		Changes made while this was a work item of the HTTP Working Group:
	E.6. Since draft-ietf-httpbis-jfv-00		E.6. Since draft-ietf-httpbis-jfv-00
	Added example for "Accept-Encoding" (inspired by Kazuho's feedback),		Added example for "Accept-Encoding" (inspired by Kazuho's feedback),
	showing a potential way to optimize the format when default values		showing a potential way to optimize the format when default values
	apply.		apply.
	E.7. Since draft-ietf-httpbis-jfv-01		E.7. Since draft-ietf-httpbis-jfv-01
	Add interop discussion, building on I-JSON and ECMA-262 (see		Add interop discussion, building on I-JSON and ECMA-262 (see
	<https://github.com/httpwg/http-extensions/issues/225>).		https://github.com/httpwg/http-extensions/issues/225).
	E.8. Since draft-ietf-httpbis-jfv-02		E.8. Since draft-ietf-httpbis-jfv-02
	Move non-essential parts into appendix.		Move non-essential parts into appendix.
	Updated XHR reference.		Updated XHR reference.
	E.9. Since draft-reschke-http-jfv-05		E.9. Since draft-reschke-http-jfv-05
	Add meat to "Using this Format in Header Field Definitions".		Add meat to "Using this Format in Header Field Definitions".
	skipping to change at page 16, line 31 ¶		skipping to change at page 16, line 13 ¶
	Update JSON and HSTRUCT references.		Update JSON and HSTRUCT references.
	FEATUREPOL doesn't use JSON syntax anymore.		FEATUREPOL doesn't use JSON syntax anymore.
	E.12. Since draft-reschke-http-jfv-08		E.12. Since draft-reschke-http-jfv-08
	Update HSTRUCT reference.		Update HSTRUCT reference.
	Update notes about CLEARSITE and FEATUREPOL.		Update notes about CLEARSITE and FEATUREPOL.
			E.13. Since draft-reschke-http-jfv-09
			Update HSTRUCT and FEATUREPOL references.
			Update note about REPORTING.
			Changed category to "informational".
	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
	Muenster, NW 48155		48155 Münster
	Germany		Germany
	EMail: julian.reschke@greenbytes.de		Email: julian.reschke@greenbytes.de
	URI: http://greenbytes.de/tech/webdav/		URI: http://greenbytes.de/tech/webdav/
End of changes. 56 change blocks.
	125 lines changed or deleted		122 lines changed or added
This html diff was produced by rfcdiff 1.45. The latest version is available from http://tools.ietf.org/tools/rfcdiff/