< draft-nottingham-json-home-00.txt		draft-nottingham-json-home-01.txt >
	Network Working Group M. Nottingham		Network Working Group M. Nottingham
	Internet-Draft Rackspace		Internet-Draft Rackspace
	Intended status: Informational May 9, 2012		Intended status: Informational July 5, 2012
	Expires: November 10, 2012		Expires: January 6, 2013
	Home Documents for HTTP APIs		Home Documents for HTTP APIs
	draft-nottingham-json-home-00		draft-nottingham-json-home-01
	Abstract		Abstract
	This document proposes a "home document" format for non-browser HTTP		This document proposes a "home document" format for non-browser HTTP
	clients.		clients.
	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.
	skipping to change at page 1, line 31 ¶		skipping to change at page 1, line 31 ¶
	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 November 10, 2012.		This Internet-Draft will expire on January 6, 2013.
	Copyright Notice		Copyright Notice
	Copyright (c) 2012 IETF Trust and the persons identified as the		Copyright (c) 2012 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
	skipping to change at page 2, line 17 ¶		skipping to change at page 2, line 17 ¶
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. JSON Home Documents . . . . . . . . . . . . . . . . . . . . . 3		3. JSON Home Documents . . . . . . . . . . . . . . . . . . . . . 3
	4. Resource Objects . . . . . . . . . . . . . . . . . . . . . . . 5		4. Resource Objects . . . . . . . . . . . . . . . . . . . . . . . 5
	4.1. Resolving Templated Links . . . . . . . . . . . . . . . . 5		4.1. Resolving Templated Links . . . . . . . . . . . . . . . . 5
	5. Resource Hints . . . . . . . . . . . . . . . . . . . . . . . . 6		5. Resource Hints . . . . . . . . . . . . . . . . . . . . . . . . 6
	5.1. allow . . . . . . . . . . . . . . . . . . . . . . . . . . 7		5.1. allow . . . . . . . . . . . . . . . . . . . . . . . . . . 7
	5.2. representations . . . . . . . . . . . . . . . . . . . . . 7		5.2. representations . . . . . . . . . . . . . . . . . . . . . 7
	5.3. accept-patch . . . . . . . . . . . . . . . . . . . . . . . 7		5.3. accept-patch . . . . . . . . . . . . . . . . . . . . . . . 7
	5.4. accept-post . . . . . . . . . . . . . . . . . . . . . . . 7		5.4. accept-post . . . . . . . . . . . . . . . . . . . . . . . 7
	5.5. accept-ranges . . . . . . . . . . . . . . . . . . . . . . 7		5.5. accept-put . . . . . . . . . . . . . . . . . . . . . . . . 7
	6. Creating and Serving Home Documents . . . . . . . . . . . . . 7		5.6. accept-ranges . . . . . . . . . . . . . . . . . . . . . . 8
	6.1. Managing Change in Home Documents . . . . . . . . . . . . 8		5.7. prefer . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	6.2. Evolving and Mixing APIs with Home Documents . . . . . . . 8		5.8. docs . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	6.3. Documenting APIs that use Home Documents . . . . . . . . . 8		5.9. precondition-req . . . . . . . . . . . . . . . . . . . . . 8
	7. Consuming Home Documents . . . . . . . . . . . . . . . . . . . 9		5.10. status . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 9		6. Creating and Serving Home Documents . . . . . . . . . . . . . 8
	9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9		6.1. Managing Change in Home Documents . . . . . . . . . . . . 9
	10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9		6.2. Evolving and Mixing APIs with Home Documents . . . . . . . 9
	10.1. Normative References . . . . . . . . . . . . . . . . . . . 9		6.3. Documenting APIs that use Home Documents . . . . . . . . . 10
	10.2. Informative References . . . . . . . . . . . . . . . . . . 10		7. Consuming Home Documents . . . . . . . . . . . . . . . . . . . 10
	Appendix A. Frequently Asked Questions . . . . . . . . . . . . . 10		8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
	A.1. Why not Microformats? . . . . . . . . . . . . . . . . . . 10		9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
	A.2. What about authentication? . . . . . . . . . . . . . . . . 11		10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
	A.3. What about "Faults" (i.e., errors)? . . . . . . . . . . . 11		10.1. Normative References . . . . . . . . . . . . . . . . . . . 11
	A.4. How Do I find the XML Schema / JSON Schema / etc. for		10.2. Informative References . . . . . . . . . . . . . . . . . . 11
	a particular media type? . . . . . . . . . . . . . . . . . 11		Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 12
	Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . . 11		Appendix B. Frequently Asked Questions . . . . . . . . . . . . . 12
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12		B.1. Why not Microformats? . . . . . . . . . . . . . . . . . . 12
			B.2. What about authentication? . . . . . . . . . . . . . . . . 12
			B.3. What about 'Faults' (i.e., errors)? . . . . . . . . . . . 12
			B.4. How Do I find the XML Schema / JSON Schema / etc. for
			a particular media type? . . . . . . . . . . . . . . . . . 13
			Appendix C. Open Issues . . . . . . . . . . . . . . . . . . . . . 13
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
	1. Introduction		1. Introduction
	There is an emerging preference for non-browser Web applications		There is an emerging preference for non-browser Web applications
	(colloquially, "HTTP APIs") to use a link-driven approach to their		(colloquially, "HTTP APIs") to use a link-driven approach to their
	interactions to assure loose coupling, thereby enabling extensibility		interactions to assure loose coupling, thereby enabling extensibility
	and API evolution.		and API evolution.
	This is based upon experience with previous APIs which specified		This is based upon experience with previous APIs that specified
	static URI paths (such as		static URI paths (such as
	"http://api.example.com/v1.0/widgets/abc123/properties") have		"http://api.example.com/v1.0/widgets/abc123/properties") have
	resulted in brittle, tight coupling between clients and servers.		resulted in brittle, tight coupling between clients and servers.
	Sometimes, these APIs are documented by a document format like		Sometimes, these APIs were documented by a document format like
	WADL [1] that is used as a "design-time" description; i.e., the URIs		WADL [1] that is used as a design time description; i.e., the URIs
	and other information they describe are "baked into" client		and other information they describe are "baked into" client
	implementations.		implementations.
	In contrast, a "follow your nose" API advertises the resources		In contrast, a "follow your nose" API advertises the resources
	available to clients using link relations [RFC5988] and the formats		available to clients using link relations [RFC5988] and the formats
	they support using internet media types [RFC4288]. A client can then		they support using internet media types [RFC4288]. A client can then
	decide - at "run time" - which resources to interact with based upon		decide - at run time - which resources to interact with based upon
	its capabilities (as described by link relations), and the server can		its capabilities (as described by link relations), and the server can
	safely add new resources and formats without disturbing clients that		safely add new resources and formats without disturbing clients that
	are not yet aware of them.		are not yet aware of them.
	As such, the client needs to be able to discover this information		As such, the client needs to be able to discover this information
	quickly and efficiently use it to interact with the server. Just as		quickly and efficiently use it to interact with the server. Just as
	with a human-targeted "home page" for a site, we can create a "home		with a human-targeted home page for a site, we can create a "home
	document" for a HTTP API (often, at the same URI, found through		document" for a HTTP API that describes it to non-browser clients.
	server-driven content negotiation) that describes it to non-browser
	clients.
	Of course, an HTTP API might use any format to do so; however, there		Of course, an HTTP API might use any format to do so; however, there
	are advantages to having a standard home document format. This		are advantages to having a standard home document format. This
	specification suggests one for consideration, using the JSON format		specification suggests one for consideration, using the JSON format
	[RFC4627].		[RFC4627].
	2. Requirements		2. Requirements
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	skipping to change at page 4, line 42 ¶		skipping to change at page 4, line 41 ¶
	"allow": ["GET", "PUT", "DELETE", "PATCH"],		"allow": ["GET", "PUT", "DELETE", "PATCH"],
	"representations": ["application/json"],		"representations": ["application/json"],
	"accept-patch": ["application/json-patch"],		"accept-patch": ["application/json-patch"],
	"accept-post": ["application/xml"],		"accept-post": ["application/xml"],
	"accept-ranges": ["bytes"]		"accept-ranges": ["bytes"]
	}		}
	}		}
	}		}
	}		}
	Here, we have a home document that links two a resource, "/widgets/"		Here, we have a home document that links to a resource, "/widgets/"
	with the relation "http://example.org/rel/widgets", and also links to		with the relation "http://example.org/rel/widgets". It also links to
	one or more with the relation type "http://example.org/rel/widget"		an undefined number of resources with the relation type
	using a URI Template [RFC6570].		"http://example.org/rel/widget" using a URI Template [RFC6570], along
			with a mapping of several identifiers to specific variables for use
			in that template.
	It also gives several hints about interacting with the latter		It also gives several hints about interacting with the latter
	"widget" resources, including the HTTP methods usable with them, the		"widget" resources, including the HTTP methods usable with them, the
	patch formats they accept, and the fact that they support partial		patch formats they accept, and the fact that they support partial
	requests [RFC2616] using the "bytes" range-specifier.		requests [I-D.ietf-httpbis-p5-range] using the "bytes" range-
			specifier.
	It gives no such hints about the "widgets" resource. This does not		It gives no such hints about the "widgets" resource. This does not
	mean that it (for example) doesn't support any HTTP methods; it means		mean that it (for example) doesn't support any HTTP methods; it means
	that the client will need to discover this by interacting with the		that the client will need to discover this by interacting with the
	resource, and/or examining the documentation for its link relation		resource, and/or examining the documentation for its link relation
	type.		type.
	4. Resource Objects		4. Resource Objects
	A Resource Object links to resources of the defined type using one of		A Resource Object links to resources of the defined type using one of
	two mechanisms; either a direct link (in which case there is exactly		two mechanisms; either a direct link (in which case there is exactly
	one resource of that relation type associated with the API), or a		one resource of that relation type associated with the API), or a
	templated link, in which case there are zero to many such resources.		templated link, in which case there are zero to many such resources.
			Resource Objects MUST have only and exactly one of the "href" and
			"href-template" properties.
	Direct links are indicated with an "href" property, whose value is a		Direct links are indicated with an "href" property, whose value is a
	URI [RFC3986].		URI [RFC3986].
	Templated links are indicated with an "href-template" property, whose		Templated links are indicated with an "href-template" property, whose
	value is a URI Template [RFC6570]. When "href-template" is present,		value is a URI Template [RFC6570]. When "href-template" is present,
	the Resource Object MUST have a "href-vars" property; see "Resolving		the Resource Object MUST have a "href-vars" property; see "Resolving
	Templated Links".		Templated Links".
	Resource Objects MUST have exactly one of the "href" and "href-vars"
	properties.
	In both forms, the links that "href" and "href-template" refer to are		In both forms, the links that "href" and "href-template" refer to are
	URI-references [RFC3986] whose base URI is that of the JSON Home		URI-references [RFC3986] whose base URI is that of the JSON Home
	Document itself.		Document itself.
	Resource Objects MAY also have a "hints" property, whose value is an		Resource Objects MAY also have a "hints" property, whose value is an
	object that uses named Resource Hints as its properties.		object that uses named Resource Hints as its properties.
	4.1. Resolving Templated Links		4.1. Resolving Templated Links
	A URI can be derived from a Templated Link by treating the "href-		A URI can be derived from a Templated Link by treating the "href-
	skipping to change at page 6, line 38 ¶		skipping to change at page 6, line 38 ¶
	Resource hints allow clients to find relevant information about		Resource hints allow clients to find relevant information about
	interacting with a resource beforehand, as a means of optimising		interacting with a resource beforehand, as a means of optimising
	communications, as well as advertising available behaviours (e.g., to		communications, as well as advertising available behaviours (e.g., to
	aid in laying out a user interface for consuming the API).		aid in laying out a user interface for consuming the API).
	Hints are just that - they are not a "contract", and are to only be		Hints are just that - they are not a "contract", and are to only be
	taken as advisory. The runtime behaviour of the resource always		taken as advisory. The runtime behaviour of the resource always
	overrides hinted information.		overrides hinted information.
	For example, a resource might hint that the PUT method is allowed on		For example, a resource might hint that the PUT method is allowed on
	all "widget" resources. this means that generally, the user has the		all "widget" resources. This means that generally, the user has the
	ability to PUT to a particular resource, but a specific resource may		ability to PUT to a particular resource, but a specific resource
	reject a PUT based upon access control or other considerations. More		could reject a PUT based upon access control or other considerations.
	fine-grained information might be gathered by interacting with the		More fine-grained information might be gathered by interacting with
	resource (e.g., via a GET), or by another resource "containing" it		the resource (e.g., via a GET), or by another resource "containing"
	(such as a "widgets" collection).		it (such as a "widgets" collection).
	This specification defines a set of common hints, based upon		This specification defines a set of common hints, based upon
	information that's discoverable by directly interacting with		information that's discoverable by directly interacting with
	resources. A future draft will explain how to define new hints.		resources. A future draft will explain how to define new hints.
	5.1. allow		5.1. allow
	Hints the HTTP methods that the current client will be able to use to		Hints the HTTP methods that the current client will be able to use to
	interact with the resource; equivalent to the Allow HTTP response		interact with the resource; equivalent to the Allow HTTP response
	header.		header.
	skipping to change at page 7, line 23 ¶		skipping to change at page 7, line 23 ¶
	5.2. representations		5.2. representations
	Hints the representation types that the resource produces and		Hints the representation types that the resource produces and
	consumes, using the GET and PUT methods respectively, subject to the		consumes, using the GET and PUT methods respectively, subject to the
	'allow' hint.		'allow' hint.
	Content MUST be an array of strings, containing media types.		Content MUST be an array of strings, containing media types.
	5.3. accept-patch		5.3. accept-patch
	Hints the PATCH request formats accepted by the resource for this		Hints the PATCH request formats [RFC5789] accepted by the resource
	client; equivalent to the Accept-Patch HTTP response header.		for this client; equivalent to the Accept-Patch HTTP response header.
	Content MUST be an array of strings, containing media types.		Content MUST be an array of strings, containing media types.
			When this hint is present, "PATCH" SHOULD be listed in the "allow"
			hint.
	5.4. accept-post		5.4. accept-post
	Hints the POST request formats accepted by the resource for this		Hints the POST request formats accepted by the resource for this
	client.		client.
	Content MUST be an array of strings, containing media types.		Content MUST be an array of strings, containing media types.
	5.5. accept-ranges		When this hint is present, "POST" SHOULD be listed in the "allow"
			hint.
			5.5. accept-put
			Hints the PUT request formats accepted by the resource for this
			client.
			Content MUST be an array of strings, containing media types. If
			absent, a client MAY assume that any format indicated by the
			'representations' hint is acceptable in a PUT.
			When this hint is present, "PUT" SHOULD be listed in the "allow"
			hint.
			5.6. accept-ranges
	Hints the range-specifiers available to the client for this resource;		Hints the range-specifiers available to the client for this resource;
	equivalent to the Accept-Ranges HTTP response header.		equivalent to the Accept-Ranges HTTP response header
			[I-D.ietf-httpbis-p5-range].
	Content MUST be an array of strings, containing HTTP range-		Content MUST be an array of strings, containing HTTP range-
	specifiers.		specifiers.
			5.7. prefer
			Hints the preferences [I-D.snell-http-prefer] supported by the
			resource. Note that, as per that specifications, a preference can be
			ignored by the server.
			Content MUST be an array of strings, contain preferences.
			5.8. docs
			Hints the location for human-readable documentation for the relation
			type of the resource.
			Content MUST be a string containing an absolute-URI [RFC3986]
			referring to documentation that SHOULD be in HTML format.
			5.9. precondition-req
			Hints that the resource requires state-changing requests (e.g., PUT,
			PATCH) to include a precondition, as per
			[I-D.ietf-httpbis-p4-conditional], to avoid conflicts due to
			concurrent updates.
			Content MUST be an array of strings, with possible values "etag" and
			"last-modified" indicating type type of precondition expected.
			5.10. status
			Hints the status of the resource.
			Content MUST be a string; possible values are:
			o "deprecated" - indicates that use of the resource is not
			recommended, but it can still be used.
	6. Creating and Serving Home Documents		6. Creating and Serving Home Documents
	When making a home document available, there are a few things to keep		When making a home document available, there are a few things to keep
	in mind:		in mind:
	o A home document is best located at a memorable URI, because its		o A home document is best located at a memorable URI, because its
	URI will effectively become the URI for the API itself to clients.		URI will effectively become the URI for the API itself to clients.
	o Home documents can be personalised, just as "normal" home pages		o Home documents can be personalised, just as "normal" home pages
	can. For example, you might advertise different URIs, and/or		can. For example, you might advertise different URIs, and/or
	different kinds of link relations, depending on the client's		different kinds of link relations, depending on the client's
	identity.		identity.
	o Home documents SHOULD be assigned a freshness lifetime (e.g.,		o Home documents SHOULD be assigned a freshness lifetime (e.g.,
	"Cache-Control: max-age=3600") so that clients can cache them, to		"Cache-Control: max-age=3600") so that clients can cache them, to
	avoid having to fetch it every time the client interacts with the		avoid having to fetch it every time the client interacts with the
	service.		service.
	o Custom link relation types, as well as the URIs for variables,		o Custom link relation types, as well as the URIs for variables,
	should lead to documentation for those constructs.		should lead to documentation for those constructs.
	skipping to change at page 9, line 24 ¶		skipping to change at page 10, line 29 ¶
	will scan the Resources Object for the link relation(s) that it is		will scan the Resources Object for the link relation(s) that it is
	interested in, and then to interact with the resource(s) referred to.		interested in, and then to interact with the resource(s) referred to.
	Resource Hints can be used to optimise communication with the client,		Resource Hints can be used to optimise communication with the client,
	as well as to inform as to the permissible actions (e.g., whether PUT		as well as to inform as to the permissible actions (e.g., whether PUT
	is likely to be supported).		is likely to be supported).
	Note that the home document is a "living" document; it does not		Note that the home document is a "living" document; it does not
	represent a "contract", but rather is expected to be inspected before		represent a "contract", but rather is expected to be inspected before
	each interaction. In particular, links from the home document MUST		each interaction. In particular, links from the home document MUST
	NOT be assumed to be valid beyond the freshness lifetime of the home		NOT be assumed to be valid beyond the freshness lifetime of the home
	document, as per HTTP's caching model [RFC2616].		document, as per HTTP's caching model [I-D.ietf-httpbis-p6-cache].
	As a result, clients SHOULD cache the home document (as per		As a result, clients SHOULD cache the home document (as per
	[RFC2616], to avoid fetching it before every interaction (which would		[I-D.ietf-httpbis-p6-cache]), to avoid fetching it before every
	otherwise be required).		interaction (which would otherwise be required).
	Likewise, a client encountering a 404 Not Found on a link SHOULD		Likewise, a client encountering a 404 Not Found on a link SHOULD
	obtain a fresh copy of the home document, to assure that it is up-to-		obtain a fresh copy of the home document, to assure that it is up-to-
	date.		date.
	8. Security Considerations		8. Security Considerations
	TBD		TBD
	9. IANA Considerations		9. IANA Considerations
	skipping to change at page 9, line 43 ¶		skipping to change at page 11, line 4 ¶
	8. Security Considerations		8. Security Considerations
	TBD		TBD
	9. IANA Considerations		9. IANA Considerations
	TBD		TBD
	10. References		10. References
	10.1. Normative References		10.1. Normative References
			[I-D.ietf-httpbis-p6-cache]
			Fielding, R., Lafon, Y., Nottingham, M., and J. Reschke,
			"HTTP/1.1, part 6: Caching",
			draft-ietf-httpbis-p6-cache-19 (work in progress),
			March 2012.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
	Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
	Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
	[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform		[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
	Resource Identifier (URI): Generic Syntax", STD 66,		Resource Identifier (URI): Generic Syntax", STD 66,
	RFC 3986, January 2005.		RFC 3986, January 2005.
	[RFC4627] Crockford, D., "The application/json Media Type for		[RFC4627] Crockford, D., "The application/json Media Type for
	JavaScript Object Notation (JSON)", RFC 4627, July 2006.		JavaScript Object Notation (JSON)", RFC 4627, July 2006.
	[RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010.		[RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010.
	[RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,		[RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
	and D. Orchard, "URI Template", RFC 6570, March 2012.		and D. Orchard, "URI Template", RFC 6570, March 2012.
	10.2. Informative References		10.2. Informative References
			[I-D.ietf-httpbis-p4-conditional]
			Fielding, R., Lafon, Y., and J. Reschke, "HTTP/1.1, part
			4: Conditional Requests",
			draft-ietf-httpbis-p4-conditional-19 (work in progress),
			March 2012.
			[I-D.ietf-httpbis-p5-range]
			Fielding, R., Lafon, Y., and J. Reschke, "HTTP/1.1, part
			5: Range Requests and Partial Responses",
			draft-ietf-httpbis-p5-range-19 (work in progress),
			March 2012.
			[I-D.snell-http-prefer]
			Snell, J., "Prefer Header for HTTP",
			draft-snell-http-prefer-12 (work in progress),
			February 2012.
	[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and		[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
	Registration Procedures", BCP 13, RFC 4288, December 2005.		Registration Procedures", BCP 13, RFC 4288, December 2005.
			[RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP",
			RFC 5789, March 2010.
	URIs		URIs
	[1] <http://www.w3.org/Submission/wadl/>		[1] <http://www.w3.org/Submission/wadl/>
	[2] <http://microformats.org/>		[2] <http://microformats.org/>
	Appendix A. Frequently Asked Questions		Appendix A. Acknowledgements
	A.1. Why not Microformats?		Thanks to Mike Amundsen, Bill Burke, Graham Klyne, Leif Hedstrom, and
			Jeni Tennison for their suggestions and feedback.
			Appendix B. Frequently Asked Questions
			B.1. Why not Microformats?
	Browser-centric Web applications use HTML as their representation		Browser-centric Web applications use HTML as their representation
	format of choice. While it is possible to augment HTML for non-		format of choice. While it is possible to augment HTML for non-
	browser clients (using techniques like Microformats [2] ), a few		browser clients (using techniques like Microformats [2] ), a few
	issues become evident when doing so:		issues become evident when doing so:
	o HTML has a very forgiving syntax. While this is appropriate for		o HTML has a very forgiving syntax. While this is appropriate for
	browsers (especially considering that there are many million HTML		browsers (especially considering that there are many million HTML
	authors in the world), it makes for a less-than-precise language		authors in the world), it makes for a less-than-precise language
	for machines, resulting in both overhead (parsing and		for machines, resulting in both overhead (parsing and
	skipping to change at page 11, line 9 ¶		skipping to change at page 12, line 40 ¶
	o HTML is presentation-centric, making it tempting to reformat it		o HTML is presentation-centric, making it tempting to reformat it
	from time to time, to improve the "look and feel" of a page.		from time to time, to improve the "look and feel" of a page.
	However, doing so can cause comparatively brittle non-browser		However, doing so can cause comparatively brittle non-browser
	clients to lose their understanding of the content's semantics,		clients to lose their understanding of the content's semantics,
	unless very careful controls are in place.		unless very careful controls are in place.
	Because of this, it's most practical to define a separate format, and		Because of this, it's most practical to define a separate format, and
	JSON is easily machine-readable, precise, and has a better chance of		JSON is easily machine-readable, precise, and has a better chance of
	being managed for stability.		being managed for stability.
	A.2. What about authentication?		B.2. What about authentication?
	In HTTP, authentication is discoverable by interacting with the		In HTTP, authentication is discoverable by interacting with the
	resource (usually, by getting a 401 Unauthorized response status		resource (usually, by getting a 401 Unauthorized response status
	code, along with one or more challenges). While the home document		code, along with one or more challenges). While the home document
	could hint it, this isn't yet done, to avoid possible security		could hint it, this isn't yet done, to avoid possible security
	complications.		complications.
	A.3. What about "Faults" (i.e., errors)?		B.3. What about 'Faults' (i.e., errors)?
	In HTTP, errors are conveyed by HTTP status codes. While this		In HTTP, errors are conveyed by HTTP status codes. While this
	specification could (and even may) allow enumeration of possible		specification could (and even may) allow enumeration of possible
	error conditions, there's a concern that this will encourage		error conditions, there's a concern that this will encourage
	applications to define many such "faults", leading to tight coupling		applications to define many such "faults", leading to tight coupling
	between the application and its clients.		between the application and its clients.
	So, this is an area of possible future development; if any such		So, this is an area of possible future development; if any such
	mechanism appears here, it's likely to be quite restricted.		mechanism appears here, it's likely to be quite restricted.
	A.4. How Do I find the XML Schema / JSON Schema / etc. for a particular		B.4. How Do I find the XML Schema / JSON Schema / etc. for a particular
	media type?		media type?
	That isn't addressed by home documents. Ultimately, it's up to the		That isn't addressed by home documents. Ultimately, it's up to the
	media type accepted and generated by resources to define and		media type accepted and generated by resources to define and
	constrain (or not) their syntax.		constrain (or not) their syntax.
	Appendix B. Open Issues		Appendix C. Open Issues
	The following is a list of placeholders for open issues.		The following is a list of placeholders for open issues.
	o Refining and extending representation formats - "application/xml",		o Refining and extending representation formats - "application/xml",
	for example, isn't enough. While a media type for every		for example, isn't enough. While a media type for every
	representation is one answer, something like 'profile' might be		representation is one answer, something like 'profile' might be
	good too.		good too.
	o Object for contact details - do we need an object that describes		o Object for contact details - do we need an object that describes
	who's running the API, etc?		who's running the API, etc?
	o Defining new hints - guidance is needed on minting new hints.		o Defining new hints - guidance is needed on minting new hints.
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