draft-reschke-http-jfv-04.txt		draft-reschke-http-jfv-05.txt
	Network Working Group J. Reschke		Network Working Group J. Reschke
	Internet-Draft greenbytes		Internet-Draft greenbytes
	Intended status: Standards Track June 23, 2016		Intended status: Standards Track December 16, 2016
	Expires: December 25, 2016		Expires: June 19, 2017
	A JSON Encoding for HTTP Header Field Values		A JSON Encoding for HTTP Header Field Values
	draft-reschke-http-jfv-04		draft-reschke-http-jfv-05
	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		the Hypertext Transfer Protocol (HTTP) mailing list at
	ietf-http-wg@w3.org [1], which may be joined by sending a message		ietf-http-wg@w3.org [1], which may be joined by sending a message
	with subject "subscribe" to ietf-http-wg-request@w3.org [2].		with subject "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 A.4.		The changes in this draft are summarized in Appendix C.5.
	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 http://datatracker.ietf.org/drafts/current/.		Drafts is at http://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 December 25, 2016.		This Internet-Draft will expire on June 19, 2017.
	Copyright Notice		Copyright Notice
	Copyright (c) 2016 IETF Trust and the persons identified as the		Copyright (c) 2016 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
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://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
	skipping to change at page 2, line 24 ¶		skipping to change at page 2, line 24 ¶
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are 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 . . . . . . . . . . . . . . . . . . . . 3		2. Data Model and Format . . . . . . . . . . . . . . . . . . . . 3
	3. Sender Requirements . . . . . . . . . . . . . . . . . . . . . 4		3. Sender Requirements . . . . . . . . . . . . . . . . . . . . . 4
	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. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 5		6. Deployment Considerations . . . . . . . . . . . . . . . . . . 5
	6.1. Content-Length . . . . . . . . . . . . . . . . . . . . . . 5		7. Interoperability Considerations . . . . . . . . . . . . . . . 5
	6.2. Content-Disposition . . . . . . . . . . . . . . . . . . . 6		7.1. Encoding and Characters . . . . . . . . . . . . . . . . . 5
	6.3. WWW-Authenticate . . . . . . . . . . . . . . . . . . . . . 7		7.2. Numbers . . . . . . . . . . . . . . . . . . . . . . . . . 6
	7. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 8		7.3. Object Constraints . . . . . . . . . . . . . . . . . . . . 6
	8. Deployment Considerations . . . . . . . . . . . . . . . . . . 8		8. Internationalization Considerations . . . . . . . . . . . . . 6
	9. Internationalization Considerations . . . . . . . . . . . . . 8		9. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	10. Security Considerations . . . . . . . . . . . . . . . . . . . 8		10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
	11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9		10.1. Normative References . . . . . . . . . . . . . . . . . . . 7
	11.1. Normative References . . . . . . . . . . . . . . . . . . . 9		10.2. Informative References . . . . . . . . . . . . . . . . . . 7
	11.2. Informative References . . . . . . . . . . . . . . . . . . 9		Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 8
	Appendix A. Change Log (to be removed by RFC Editor before		A.1. Content-Length . . . . . . . . . . . . . . . . . . . . . . 8
	publication) . . . . . . . . . . . . . . . . . . . . 10		A.2. Content-Disposition . . . . . . . . . . . . . . . . . . . 9
	A.1. Since draft-reschke-http-jfv-00 . . . . . . . . . . . . . 10		A.3. WWW-Authenticate . . . . . . . . . . . . . . . . . . . . . 10
	A.2. Since draft-reschke-http-jfv-01 . . . . . . . . . . . . . 10		A.4. Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 11
	A.3. Since draft-reschke-http-jfv-02 . . . . . . . . . . . . . 10		Appendix B. Discussion . . . . . . . . . . . . . . . . . . . . . 12
	A.4. Since draft-reschke-http-jfv-03 . . . . . . . . . . . . . 11		Appendix C. Change Log (to be removed by RFC Editor before
	Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 11		publication) . . . . . . . . . . . . . . . . . . . . 12
			C.1. Since draft-reschke-http-jfv-00 . . . . . . . . . . . . . 12
			C.2. Since draft-reschke-http-jfv-01 . . . . . . . . . . . . . 12
			C.3. Since draft-reschke-http-jfv-02 . . . . . . . . . . . . . 13
			C.4. Since draft-reschke-http-jfv-03 . . . . . . . . . . . . . 13
			C.5. Since draft-reschke-http-jfv-04 . . . . . . . . . . . . . 13
			C.5.1. Since draft-ietf-httpbis-jfv-00 . . . . . . . . . . . 13
			C.5.2. Since draft-ietf-httpbis-jfv-01 . . . . . . . . . . . 13
			C.5.3. Since draft-ietf-httpbis-jfv-02 . . . . . . . . . . . 13
			Appendix D. Acknowledgements . . . . . . . . . . . . . . . . . . 13
	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
	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.
	skipping to change at page 4, line 29 ¶		skipping to change at page 4, line 29 ¶
	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).		([RFC7159], 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 [RFC7159], Section 2,
	; post-processed so that only VCHAR characters		; post-processed so that only VCHAR characters
	skipping to change at page 5, line 32 ¶		skipping to change at page 5, line 32 ¶
	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
	[[anchor5: Explain what a definition of a new header field needs to		[[anchor5: Explain what a definition of a new header field needs to
	do precisely to use this format, mention must-ignore extensibiliy]]		do precisely to use this format, mention must-ignore extensibility]]
	6. Examples		6. Deployment Considerations
			This JSON-based syntax will only apply to newly introduced header
			fields, thus backwards compatibility is not a problem. That being
			said, it is conceivable that there is existing code that might trip
			over double quotes not being used for HTTP's quoted-string syntax
			(Section 3.2.6 of [RFC7230]).
			7. Interoperability Considerations
			The "I-JSON Message Format" specification ([RFC7493]) addresses known
			JSON interoperability pain points. This specification borrows from
			the requirements made over there:
			7.1. Encoding and Characters
			This specification requires that field values use only US-ASCII
			characters, and thus by definition use a subset of UTF-8 (Section 2.1
			of [RFC7493]).
			7.2. Numbers
			Be aware of the issues around number precision, as discussed in
			Section 2.2 of [RFC7493].
			7.3. Object Constraints
			As described in Section 4 of [RFC7159], JSON parser implementations
			differ in the handling of duplicate object names. Therefore, senders
			MUST NOT use duplicate object names, and recipients SHOULD either
			treat field values with duplicate names as invalid (consistent with
			[RFC7493], Section 2.3) or use the lexically last value (consistent
			with [ECMA-262], Section 24.3.1.1).
			Furthermore, ordering of object members is not significant and can
			not be relied upon.
			8. Internationalization Considerations
			In HTTP/1.1, header field values are represented by octet sequences,
			usually used to transmit ASCII characters, with restrictions on the
			use of certain control characters, and no associated default
			character encoding, nor a way to describe it ([RFC7230], Section
			3.2). HTTP/2 does not change this.
			This specification maps all characters which can cause problems to
			JSON escape sequences, thereby solving the HTTP header field
			internationalization problem.
			Future specifications of HTTP might change to allow non-ASCII
			characters natively. In that case, header fields using the syntax
			defined by this specification would have a simple migration path (by
			just stopping to require escaping of non-ASCII characters).
			9. Security Considerations
			Using JSON-shaped field values is believed to not introduce any new
			threads beyond those described in Section 12 of [RFC7159], namely the
			risk of recipients using the wrong tools to parse them.
			Other than that, any syntax that makes extensions easy can be used to
			smuggle information through field values; however, this concern is
			shared with other widely used formats, such as those using parameters
			in the form of name/value pairs.
			10. References
			10.1. Normative References
			[RFC0020] Cerf, V., "ASCII format for network interchange",
			STD 80, RFC 20, DOI 10.17487/RFC0020, October 1969,
			<http://www.rfc-editor.org/info/rfc20>.
			[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for
			Syntax Specifications: ABNF", STD 68, RFC 5234,
			DOI 10.17487/RFC5234, January 2008,
			<http://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,
			<http://www.rfc-editor.org/info/rfc7159>.
			[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
			Transfer Protocol (HTTP/1.1): Message Syntax and
			Routing", RFC 7230, DOI 10.17487/RFC7230,
			June 2014,
			<http://www.rfc-editor.org/info/rfc7230>.
			[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
			Transfer Protocol (HTTP/1.1): Semantics and
			Content", RFC 7231, DOI 10.17487/RFC7231,
			June 2014,
			<http://www.rfc-editor.org/info/rfc7231>.
			[RFC7493] Bray, T., Ed., "The I-JSON Message Format",
			RFC 7493, DOI 10.17487/RFC7493, March 2015,
			<http://www.rfc-editor.org/info/rfc7493>.
			10.2. Informative References
			[ECMA-262] Ecma International, "ECMA-262 6th Edition, The
			ECMAScript 2015 Language Specification",
			Standard ECMA-262, June 2015,
			<http://www.ecma-international.org/ecma-262/6.0/>.
			[ISO-8859-1] International Organization for Standardization,
			"Information technology -- 8-bit single-byte coded
			graphic character sets -- Part 1: Latin alphabet
			No. 1", ISO/IEC 8859-1:1998, 1998.
			[KEY] Fielding, R. and M. Nottingham, "The Key HTTP
			Response Header Field", draft-ietf-httpbis-key-01
			(work in progress), March 2016.
			[RFC5987] Reschke, J., "Character Set and Language Encoding
			for Hypertext Transfer Protocol (HTTP) Header Field
			Parameters", RFC 5987, DOI 10.17487/RFC5987,
			August 2010,
			<http://www.rfc-editor.org/info/rfc5987>.
			[RFC6266] Reschke, J., "Use of the Content-Disposition Header
			Field in the Hypertext Transfer Protocol (HTTP)",
			RFC 6266, DOI 10.17487/RFC6266, June 2011,
			<http://www.rfc-editor.org/info/rfc6266>.
			[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
			Internationalization in the IETF", BCP 166,
			RFC 6365, DOI 10.17487/RFC6365, September 2011,
			<http://www.rfc-editor.org/info/rfc6365>.
			[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
			Transfer Protocol (HTTP/1.1): Authentication",
			RFC 7235, DOI 10.17487/RFC7235, June 2014,
			<http://www.rfc-editor.org/info/rfc7235>.
			[XMLHttpRequest] WhatWG, "XMLHttpRequest",
			<https://xhr.spec.whatwg.org/>.
			URIs
			[1] <mailto:ietf-http-wg@w3.org>
			[2] <mailto:ietf-http-wg-request@w3.org?subject=subscribe>
			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.
	6.1. 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], Section		So the field value is similar to a JSON number ([RFC7159], Section
	6).		6).
	Content-Length is restricted to a single field instance, as it		Content-Length is restricted to a single field instance, as it
	skipping to change at page 6, line 20 ¶		skipping to change at page 9, line 21 ¶
	...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)
	6.2. 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]:
	Attachment; filename=example.html		Attachment; filename=example.html
	has a disposition type of "Attachment", with filename parameter value		has a disposition type of "Attachment", with filename parameter value
	skipping to change at page 7, line 10 ¶		skipping to change at page 10, line 12 ¶
	defined in [RFC5987], representing a filename starting with the		defined in [RFC5987], representing a filename starting with the
	Unicode character U+20AC (EURO SIGN), followed by " rates". If the		Unicode character U+20AC (EURO SIGN), followed by " rates". If the
	definition of Content-Disposition would have used the format proposed		definition of Content-Disposition would have used the format proposed
	here, the workaround involving the "parameter*" syntax would not have		here, the workaround involving the "parameter*" syntax would not have
	been needed at all.		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" } }
	6.3. 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":
	WWW-Authenticate = 1#challenge		WWW-Authenticate = 1#challenge
	...where a challenge consists of a scheme with optional parameters:		...where a challenge consists of a scheme with optional parameters:
	challenge = auth-scheme [ 1*SP ( token68 / #auth-param ) ]		challenge = auth-scheme [ 1*SP ( token68 / #auth-param ) ]
	skipping to change at page 8, line 5 ¶		skipping to change at page 11, line 9 ¶
	}		}
	}		}
	]		]
	...which would translate to a header field value of:		...which would translate to a header field value of:
	{ "Newauth" : { "realm": "apps", "type" : 1,		{ "Newauth" : { "realm": "apps", "type" : 1,
	"title": "Login to \"apps\"" }},		"title": "Login to \"apps\"" }},
	{ "Basic" : { "realm": "simple"}}		{ "Basic" : { "realm": "simple"}}
	7. Discussion		A.4. Accept-Encoding
	This approach uses a default of "JSON array", using implicit array
	markers. An alternative would be a default of "JSON object". This
	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
	fields would be gone. A hybrid approach might make sense, as long as
	it doesn't require any heuristics on the recipient's side.
	Note: a concrete proposal was made by Kazuho Oku in <https://		The Accept-Encoding header field value is defined in Section 5.3.4 of
	lists.w3.org/Archives/Public/ietf-http-wg/2016JanMar/0155.html>.		[RFC7231] as a list of codings, each of which allowing a weight
			parameter 'q':
	[[anchor7: Use of generic libs vs compactness of field values..]]		Accept-Encoding = #( codings [ weight ] )
			codings = content-coding / "identity" / "*"
			weight = OWS ";" OWS "q=" qvalue
			qvalue = ( "0" [ "." 0*3DIGIT ] )
			/ ( "1" [ "." 0*3("0") ] )
	[[anchor8: Mention potential "Key" header field extension ([KEY]).]]		An example for a complex header field value given in the definition
			of the header field is:
	8. Deployment Considerations		gzip;q=1.0, identity; q=0.5, *;q=0
	This JSON-based syntax will only apply to newly introduced header		Due to the defaulting rules for the quality value ([RFC7231], Section
	fields, thus backwards compatibility is not a problem. That being		5.3.1), this could also be written as:
	said, it is conceivable that there is existing code that might trip
	over double quotes not being used for HTTP's quoted-string syntax
	(Section 3.2.6 of [RFC7230]).
	9. Internationalization Considerations		gzip, identity; q=0.5, *; q=0
	In HTTP/1.1, header field values are represented by octet sequences,		A JSON representation could be:
	usually used to transmit ASCII characters, with restrictions on the
	use of certain control characters, and no associated default
	character encoding, nor a way to describe it ([RFC7230], Section
	3.2). HTTP/2 does not change this.
	This specification maps all characters which can cause problems to		[
	JSON escape sequences, thereby solving the HTTP header field		{
	internationalization problem.		"gzip" : {
			}
			},
			{
			"identity" : {
			"q": 0.5
			}
			},
			{
			"*" : {
			"q": 0
			}
			}
			]
	Future specifications of HTTP might change to allow non-ASCII		...which would translate to a header field value of:
	characters natively. In that case, header fields using the syntax
	defined by this specification would have a simple migration path (by
	just stopping to require escaping of non-ASCII characters).
	10. Security Considerations		{"gzip": {}}, {"identity": {"q": 0.5}}, {"*": {"q": 0}}
	Using JSON-shaped field values is believed to not introduce any new		In this example, the part about "gzip" appears unnecessarily verbose,
	threads beyond those described in Section 12 of [RFC7159], namely the		as the value is just an empty object. A simpler notation would
	risk of recipients using the wrong tools to parse them.		collapse members like these to string literals:
	Other than that, any syntax that makes extensions easy can be used to		"gzip", {"identity": {"q": 0.5}}, {"*": {"q": 0}}
	smuggle information through field values; however, this concern is
	shared with other widely used formats, such as those using parameters
	in the form of name/value pairs.
	11. References		If this is desirable, the header field definition could allow both
			string literals and objects, and define that a mere string literal
			would be mapped to a member whose name is given by the string
			literal, and the value is an empty object.
	11.1. Normative References		For what it's worth, one of the most common cases for 'Accept-
			Encoding' would become:
	[RFC0020] Cerf, V., "ASCII format for network interchange",		"gzip", "deflate"
	STD 80, RFC 20, DOI 10.17487/RFC0020, October 1969,
	<http://www.rfc-editor.org/info/rfc20>.
	[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for		which would be only a small overhead over the original format.
	Syntax Specifications: ABNF", STD 68, RFC 5234,
	DOI 10.17487/RFC5234, January 2008,
	<http://www.rfc-editor.org/info/rfc5234>.
	[RFC7159] Bray, T., "The JavaScript Object Notation (JSON)		Appendix B. Discussion
	Data Interchange Format", RFC 7159, DOI 10.17487/
	RFC7159, March 2014,
	<http://www.rfc-editor.org/info/rfc7159>.
	[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext		This approach uses a default of "JSON array", using implicit array
	Transfer Protocol (HTTP/1.1): Message Syntax and		markers. An alternative would be a default of "JSON object". This
	Routing", RFC 7230, DOI 10.17487/RFC7230,		would simplify the syntax for non-list-typed header fields, but all
	June 2014,		the benefits of having the same data model for both types of header
	<http://www.rfc-editor.org/info/rfc7230>.		fields would be gone. A hybrid approach might make sense, as long as
			it doesn't require any heuristics on the recipient's side.
	[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext		Note: a concrete proposal was made by Kazuho Oku in <https://
	Transfer Protocol (HTTP/1.1): Semantics and		lists.w3.org/Archives/Public/ietf-http-wg/2016JanMar/0155.html>.
	Content", RFC 7231, DOI 10.17487/RFC7231,
	June 2014,
	<http://www.rfc-editor.org/info/rfc7231>.
	11.2. Informative References		[[anchor15: Use of generic libs vs compactness of field values..]]
	[ISO-8859-1] International Organization for Standardization,		[[anchor16: Mention potential "Key" header field extension ([KEY]).]]
	"Information technology -- 8-bit single-byte coded
	graphic character sets -- Part 1: Latin alphabet
	No. 1", ISO/IEC 8859-1:1998, 1998.
	[KEY] Fielding, R. and M. Nottingham, "The Key HTTP		Appendix C. Change Log (to be removed by RFC Editor before publication)
	Response Header Field", draft-ietf-httpbis-key-01
	(work in progress), March 2016.
	[RFC5987] Reschke, J., "Character Set and Language Encoding		C.1. Since draft-reschke-http-jfv-00
	for Hypertext Transfer Protocol (HTTP) Header Field
	Parameters", RFC 5987, DOI 10.17487/RFC5987,
	August 2010,
	<http://www.rfc-editor.org/info/rfc5987>.
	[RFC6266] Reschke, J., "Use of the Content-Disposition Header		Editorial fixes + working on the TODOs.
	Field in the Hypertext Transfer Protocol (HTTP)",
	RFC 6266, DOI 10.17487/RFC6266, June 2011,
	<http://www.rfc-editor.org/info/rfc6266>.
	[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in		C.2. Since draft-reschke-http-jfv-01
	Internationalization in the IETF", BCP 166,
	RFC 6365, DOI 10.17487/RFC6365, September 2011,
	<http://www.rfc-editor.org/info/rfc6365>.
	[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext		Mention slightly increased risk of smuggling information in header
	Transfer Protocol (HTTP/1.1): Authentication",		field values.
	RFC 7235, DOI 10.17487/RFC7235, June 2014,
	<http://www.rfc-editor.org/info/rfc7235>.
	[XMLHttpRequest] van Kesteren, A., Aubourg, J., Song, J., and H.		C.3. Since draft-reschke-http-jfv-02
	Steen, "XMLHttpRequest Level 1", W3C Working
	Draft WD-XMLHttpRequest-20140130, January 2014, <ht
	tp://www.w3.org/TR/2014/
	WD-XMLHttpRequest-20140130/>.
	Latest version available at		Mention Kazuho Oku's proposal for abbreviated forms.
	<http://www.w3.org/TR/XMLHttpRequest/>.
	URIs		Added a bit of text about the motivation for a concrete JSON subset
			(ack Cory Benfield).
	[1] <mailto:ietf-http-wg@w3.org>		Expand I18N section.
	[2] <mailto:ietf-http-wg-request@w3.org?subject=subscribe>		C.4. Since draft-reschke-http-jfv-03
	Appendix A. Change Log (to be removed by RFC Editor before publication)		Mention relation to KEY header field.
	A.1. Since draft-reschke-http-jfv-00		C.5. Since draft-reschke-http-jfv-04
	Editorial fixes + working on the TODOs.		Between June and December 2016, this was a work item of the HTTP
			working group (see
			<https://datatracker.ietf.org/doc/draft-ietf-httpbis-jfv/>). Work
			(if any) continues now on
			<https://datatracker.ietf.org/doc/draft-reschke-http-jfv/>.
	A.2. Since draft-reschke-http-jfv-01		Changes made while this was a work item of the HTTP Working Group:
	Mention slightly increased risk of smuggling information in header		C.5.1. Since draft-ietf-httpbis-jfv-00
	field values.
	A.3. Since draft-reschke-http-jfv-02		Added example for "Accept-Encoding" (inspired by Kazuho's feedback),
			showing a potential way to optimize the format when default values
			apply.
	Mention Kazuho Oku's proposal for abbreviated forms.		C.5.2. Since draft-ietf-httpbis-jfv-01
	Added a bit of text about the motivation for a concrete JSON subset		Add interop discussion, building on I-JSON and ECMA-262 (see
	(ack Cory Benfield).		<https://github.com/httpwg/http-extensions/issues/225>).
	Expand I18N section.		C.5.3. Since draft-ietf-httpbis-jfv-02
	A.4. Since draft-reschke-http-jfv-03		Move non-essential parts into appendix.
	Mention relation to KEY header field.		Updated XHR reference.
	Appendix B. Acknowledgements		Appendix D. 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		Muenster, NW 48155
End of changes. 55 change blocks.
	140 lines changed or deleted		270 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/