draft-ietf-httpbis-jfv-02.txt		draft-ietf-httpbis-jfv-latest.txt
	HTTP Working Group J. Reschke		HTTP Working Group J. Reschke
	Internet-Draft greenbytes		Internet-Draft greenbytes
	Intended status: Standards Track October 24, 2016		Intended status: Standards Track July 6, 2024
	Expires: April 27, 2017		Expires: January 7, 2025
	A JSON Encoding for HTTP Header Field Values		A JSON Encoding for HTTP Header Field Values
	draft-ietf-httpbis-jfv-02		draft-ietf-httpbis-jfv-latest
	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)
	Discussion of this draft takes place on the HTTPBIS working group		Discussion of this draft takes place on the HTTPBIS working group
	mailing list (ietf-http-wg@w3.org), which is archived at		mailing list (ietf-http-wg@w3.org), which is archived at
	<https://lists.w3.org/Archives/Public/ietf-http-wg/>.		<https://lists.w3.org/Archives/Public/ietf-http-wg/>.
	Working Group information can be found at <http://httpwg.github.io/>;		Working Group information can be found at <http://httpwg.github.io/>;
	source code and issues list for this draft can be found at		source code and issues list for this draft can be found at
	<https://github.com/httpwg/http-extensions>.		<https://github.com/httpwg/http-extensions>.
	The changes in this draft are summarized in Appendix A.		The changes in this draft are summarized in Appendix C.
	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.
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	This Internet-Draft will expire on April 27, 2017.		This Internet-Draft will expire on January 7, 2025.
	Copyright Notice		Copyright Notice
	Copyright (c) 2016 IETF Trust and the persons identified as the		Copyright (c) 2024 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	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
	6.4. Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 8		7.3. Object Constraints . . . . . . . . . . . . . . . . . . . 6
	7. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 9		8. Internationalization Considerations . . . . . . . . . . . . . 6
	8. Deployment Considerations . . . . . . . . . . . . . . . . . . 9		9. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	9. Interoperability Considerations . . . . . . . . . . . . . . . 9		10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	9.1. Encoding and Characters . . . . . . . . . . . . . . . . . 9		10.1. Normative References . . . . . . . . . . . . . . . . . . 7
	9.2. Numbers . . . . . . . . . . . . . . . . . . . . . . . . . 10		10.2. Informative References . . . . . . . . . . . . . . . . . 7
	9.3. Object Constraints . . . . . . . . . . . . . . . . . . . . 10		Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 9
	10. Internationalization Considerations . . . . . . . . . . . . . 10		A.1. Content-Length . . . . . . . . . . . . . . . . . . . . . 9
	11. Security Considerations . . . . . . . . . . . . . . . . . . . 10		A.2. Content-Disposition . . . . . . . . . . . . . . . . . . . 9
	12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11		A.3. WWW-Authenticate . . . . . . . . . . . . . . . . . . . . 10
	12.1. Normative References . . . . . . . . . . . . . . . . . . . 11		A.4. Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 11
	12.2. Informative References . . . . . . . . . . . . . . . . . . 11		Appendix B. Discussion . . . . . . . . . . . . . . . . . . . . . 12
	Appendix A. Change Log (to be removed by RFC Editor before		Appendix C. Change Log (to be removed by RFC Editor before
	publication) . . . . . . . . . . . . . . . . . . . . 12		publication) . . . . . . . . . . . . . . . . . . . . 13
	A.1. Since draft-reschke-http-jfv-00 . . . . . . . . . . . . . 12		C.1. Since draft-reschke-http-jfv-00 . . . . . . . . . . . . . 13
	A.2. Since draft-reschke-http-jfv-01 . . . . . . . . . . . . . 12		C.2. Since draft-reschke-http-jfv-01 . . . . . . . . . . . . . 13
	A.3. Since draft-reschke-http-jfv-02 . . . . . . . . . . . . . 12		C.3. Since draft-reschke-http-jfv-02 . . . . . . . . . . . . . 13
	A.4. Since draft-reschke-http-jfv-03 . . . . . . . . . . . . . 13		C.4. Since draft-reschke-http-jfv-03 . . . . . . . . . . . . . 13
	A.5. Since draft-reschke-http-jfv-04 . . . . . . . . . . . . . 13		C.5. Since draft-reschke-http-jfv-04 . . . . . . . . . . . . . 13
	A.6. Since draft-ietf-httpbis-jfv-00 . . . . . . . . . . . . . 13		C.6. Since draft-ietf-httpbis-jfv-00 . . . . . . . . . . . . . 13
	A.7. Since draft-ietf-httpbis-jfv-01 . . . . . . . . . . . . . 13		C.7. Since draft-ietf-httpbis-jfv-01 . . . . . . . . . . . . . 13
	Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 13		C.8. Since draft-ietf-httpbis-jfv-02 . . . . . . . . . . . . . 14
			Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 14
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14
	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 5, line 31 ¶		skipping to change at page 5, line 31 ¶
	("]") octet, then		("]") octet, then
	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		[[CREF1: Explain what a definition of a new header field needs to do
	do precisely to use this format, mention must-ignore extensibility]]		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,
			<https://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,
			<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
			Protocol (HTTP/1.1): Message Syntax and Routing",
			RFC 7230, DOI 10.17487/RFC7230, June 2014,
			<https://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,
			<https://www.rfc-editor.org/info/rfc7231>.
			[RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
			DOI 10.17487/RFC7493, March 2015,
			<https://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,
			<https://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,
			<https://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,
			<https://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,
			<https://www.rfc-editor.org/info/rfc7235>.
			[XMLHttpRequest]
			WhatWG, "XMLHttpRequest", <https://xhr.spec.whatwg.org/>.
			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],
	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
	skipping to change at page 6, line 20 ¶		skipping to change at page 9, line 40 ¶
	...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 31 ¶
	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 26 ¶
	}		}
	}		}
	]		]
	...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"}}
	6.4. 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" / "*"		codings = content-coding / "identity" / "*"
	weight = OWS ";" OWS "q=" qvalue		weight = OWS ";" OWS "q=" qvalue
	qvalue = ( "0" [ "." 0*3DIGIT ] )		qvalue = ( "0" [ "." 0*3DIGIT ] )
	/ ( "1" [ "." 0*3("0") ] )		/ ( "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], Section		Due to the defaulting rules for the quality value ([RFC7231],
	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
	A JSON representation could be:		A JSON representation could be:
	[		[
	{		{
	"gzip" : {		"gzip" : {
	}		}
	},		},
	skipping to change at page 9, line 19 ¶		skipping to change at page 12, line 44 ¶
	would be mapped to a member whose name is given by the string		would be mapped to a member whose name is given by the string
	literal, and the value is an empty object.		literal, and the value is an empty object.
	For what it's worth, one of the most common cases for 'Accept-		For what it's worth, one of the most common cases for 'Accept-
	Encoding' would become:		Encoding' would become:
	"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.
	7. Discussion		Appendix B. 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 <https://		Note: a concrete proposal was made by Kazuho Oku in
	lists.w3.org/Archives/Public/ietf-http-wg/2016JanMar/0155.html>.		<https://lists.w3.org/Archives/Public/ietf-http-
			wg/2016JanMar/0155.html>.
	[[anchor7: Use of generic libs vs compactness of field values..]]
	[[anchor8: Mention potential "Key" header field extension ([KEY]).]]
	8. 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]).
	9. Interoperability Considerations
	The "I-JSON Message Format" specification ([RFC7493]) addresses known
	JSON interoperability pain points. This specification borrows from
	the requirements made over there:
	9.1. 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]).
	9.2. Numbers
	Be aware of the issues around number precision, as discussed in
	Section 2.2 of [RFC7493].
	9.3. 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.
	10. 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).
	11. 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.
	12. References
	12.1. 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>.
	12.2. 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] van Kesteren, A., Aubourg, J., Song, J., and H.		[[CREF2: Use of generic libs vs compactness of field values..]]
	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		[[CREF3: Mention potential "Key" header field extension ([KEY]).]]
	<http://www.w3.org/TR/XMLHttpRequest/>.
	Appendix A. Change Log (to be removed by RFC Editor before publication)		Appendix C. Change Log (to be removed by RFC Editor before publication)
	A.1. Since draft-reschke-http-jfv-00		C.1. Since draft-reschke-http-jfv-00
	Editorial fixes + working on the TODOs.		Editorial fixes + working on the TODOs.
	A.2. Since draft-reschke-http-jfv-01		C.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.
	A.3. Since draft-reschke-http-jfv-02		C.3. Since draft-reschke-http-jfv-02
	Mention Kazuho Oku's proposal for abbreviated forms.		Mention Kazuho Oku's proposal for abbreviated forms.
	Added a bit of text about the motivation for a concrete JSON subset		Added a bit of text about the motivation for a concrete JSON subset
	(ack Cory Benfield).		(ack Cory Benfield).
	Expand I18N section.		Expand I18N section.
	A.4. Since draft-reschke-http-jfv-03		C.4. Since draft-reschke-http-jfv-03
	Mention relation to KEY header field.		Mention relation to KEY header field.
	A.5. Since draft-reschke-http-jfv-04		C.5. Since draft-reschke-http-jfv-04
	Change to HTTP Working Group draft.		Change to HTTP Working Group draft.
	A.6. Since draft-ietf-httpbis-jfv-00		C.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.
	A.7. Since draft-ietf-httpbis-jfv-01		C.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>).
	Appendix B. Acknowledgements		C.8. Since draft-ietf-httpbis-jfv-02
			Move non-essential parts into appendix.
			Updated XHR reference.
			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
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