ldp.html
author sspeiche
Wed, 16 Jan 2013 16:43:56 -0500
changeset 43 6d2805d7c6bf
parent 42 2aeef316040a
child 58 36b2595db2ff
permissions -rw-r--r--
Added new issues ranging from 26-43. Removed closed/deferred issues: 2 & 3
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    <title>Linked Data Platform 1.0</title>
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<body>
<section id='abstract'>
A set of best practices and simple approach for a read-write Linked Data architecture, based on
HTTP access to web resources that describe their state using <abbr title="Resource Description Framework">RDF</abbr>.
</section>
 
<section>
<h1 id="intro">Introduction</h1>
	<p>This document describes the use
	of HTTP for accessing, updating, creating and deleting resources from
	servers that expose their resources as Linked Data.  It provides some
	new rules as well as clarifications and extensions of the four rules
	of Linked Data [[LINKED-DATA]]:</p>
	<p>1. Use URIs as names for things</p>
	<p>2. Use HTTP URIs so that people can look up those
		names</p>
	<p>3. When someone looks up a URI, provide useful
		information, using the standards (RDF*, <abbr title="SPARQL Protocol and RDF Query Language">SPARQL</abbr>)</p>
	<p>4. Include links to other URIs. so that they can
		discover more things</p>
	<p>The best practices and
		anti-patterns covered in this document are:</p>
	<ul>
		<li><p>
			<em>Resources</em> - a summary of the
				HTTP and RDF standard techniques and best practices that you should
				use, and anti-patterns you should avoid, when constructing clients
				and servers that read and write linked data.
			</p>
		</li>
		<li><p>
			<em>Containers</em> - defines resources
				that allow new resources to be created using HTTP POST and existing
				resources to be found using HTTP GET. 
			</p>
		</li>
	</ul>
	<p>Additionally, it is the intention
	of this document to enable additional rules and layered groupings of
	rules, such as additional specifications.  The scope is intentionally
	narrow to provide a set of key rules for reading and writing Linked
	Data that most, if not all, other specifications will depend on and
	implementations will support.</p>   
	
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/37">ISSUE-37</a></div>
	What is the LDP data model and the LDP interaction model?
	</div>
</section>
	
<section>
<h1 id="terms">Terminology</h1>

<p>Terminology is based on W3C's Architecture of the World Wide Web [[WEBARCH]] and Hyper-text Transfer Protocol [[HTTP11]].
</p>
  <dl class="glossary">
	<dt>Link</dt>
	<dd>A relationship between two resources when one resource (representation) refers to the other resource by means
		of a URI [[WEBARCH]].
		<p></p></dd>
							
	<dt>Linked Data</dt>
	<dd>As defined by Tim Berners-Lee [[LINKED-DATA]].<p></p></dd>
	
	<dt><dfn>Linked Data Platform Resource</dfn> (<dfn><abbr title="Linked Data Platform Resource">LDPR</abbr></dfn>)</dt>
	<dd>HTTP resource that conforms to the simple lifecycle
		patterns and conventions in the <a href="#ldpr">LDPRs</a> section.<p></p></dd>
		
	<dt><dfn>Linked Data Platform Container</dfn> (<dfn><abbr title="Linked Data Platform Container">LDPC</abbr></dfn>)</dt>
	<dd>LDPR that also conforms to <a href="#ldpc">additional patterns and conventions</a> for managing membership.
	<p></p></dd>
		
	<dt>Client</dt>
	<dd>A program that establishes connections for the purpose of sending requests [[HTTP11]].<p></p></dd>
	
	<dt>Server</dt>
	<dd>An application
		program that accepts connections in order to service requests by
		sending back responses. 
		<p>Any given program may be capable of being
		both a client and a server; our use of these terms refers only to
		the role being performed by the program for a particular
		connection, rather than to the program's capabilities in general.
		Likewise, any server may act as an origin server, proxy, gateway,
		or tunnel, switching behavior based on the nature of each request
		[[HTTP11]]. </p></dd>

	<dt><dfn>Membership triples</dfn></dt>
	<dd>A set of triples in an LDPC's state that lists its members.
		The membership triples of a container all have the same
		subject and predicate, and the objects of the membership triples define
		the container's members. 
	<p></p></dd>
	
	<dt><dfn>Membership subject</dfn></dt>
	<dd>The subject of all an LDPC's <a title="Membership triples">membership triples</a>.
	<p></p></dd>
	
	<dt><dfn>Membership predicate</dfn></dt>
	<dd>The predicate of all an LDPC's <a title="Membership triples">membership triples</a>.
	<p></p></dd>
  </dl>

<section>
<h2 id="conventions">Conventions Used in This Document</h2>

	<p>Sample resource representations are provided in <code>text/turtle</code>
		format [[TURTLE]].</p>
	<p>Commonly used namespace prefixes:</p>
	<pre style="word-wrap: break-word; white-space: pre-wrap;">
	@prefix dcterms: &lt;http://purl.org/dc/terms/&gt;.
	@prefix rdf:     &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt;.
	@prefix rdfs:    &lt;http://www.w3.org/2000/01/rdf-schema#&gt;.
	@prefix ldp:     &lt;http://www.w3.org/ns/ldp#&gt;.
	@prefix xsd:     &lt;http://www.w3.org/2001/XMLSchema#&gt;.</pre>
</section>
</section>
    
<section id='conformance'></section>

<section>
<h1 id="ldpr">Linked Data Platform Resources</h1>
	<p>Linked Data Platform Resources (<dfn><abbr title="Linked Data Platform Resources">LDPRs</abbr></dfn>) are HTTP resources
		that conform to the simple patterns and conventions in this section.
		HTTP requests to access, modify, create or delete LDPRs are accepted
		and processed by LDPR servers. Most LDPRs are domain-specific resources
		that contain data for an entity in some domain, which could be
		commercial, governmental, scientific, religious, or other.</p>
	<p>Some of the rules defined in this document provide
		clarification and refinement of the base Linked Data rules [[LINKED-DATA]];
		others address additional needs.</p>
	<p>The rules for Linked Data Platform Resources address basic
		questions such as:</p>
	<ul>
		<li>What resource formats should be used?</li>
		<li>How is optimistic collision detection handled for updates?</li>
		<li>What should client expectations be for changes to linked-to resources,
				such as type changes?</li>
		<li>What can servers do to ease the burden of constraints for resource
				creation?</li>
	</ul>
	<p>Additional informative guidance is available on the <a
			href="http://www.w3.org/2012/ldp/wiki/Deployment_Guide"
			class="external "
			title="Deployment Guide"
			rel="nofollow">working group's wiki</a> that addresses deployment
		questions such as:</p>
	<ul>
		<li>What literal value types should be used?</li>
		<li>Are there some typical vocabularies that should be reused?</li>
	</ul>
	<p>The following sections define the rules and
		guidelines for use of LDPRs.</p>
		
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/31">ISSUE-31</a></div>
	Proper Conformance section for LDP
	</div>
	
<section>
<h2 id="ldpr-general">General</h2>
		
	<div id="ldpr-4_1_1" class="rule">4.1.1 LDPR servers MUST at least be HTTP/1.1 conformant servers [[!HTTP11]].</div>
	<div id="ldpr-4_1_2" class="rule">4.1.2 LDPR servers MUST provide an RDF representation for LDPRs. 
	The HTTP Request-URI of the LDPR is typically the subject of most triples in the response.
	</div>
	<div id="ldpr-4_1_3" class="rule">4.1.3 LDPR servers MAY host a mixture of LDPRs and non-LDPRs. For example, it
		is common for LDPR servers to need to host binary or text resources
		that do not have useful RDF representations.
	</div>
	<div id="ldpr-4_1_4" class="rule">4.1.4 Clients can access a LDPR using multiple
			URLs, for example when DNS aliasing is used. A LDPR server MUST
			respond to each of those requests using a single consistent URL, a
			canonical URL, for the LDPR which may be found in the response's
			Location header and potentially also in the representation of the
			LDPR. Clients SHOULD use the canonical URL as an LDPR's identity;
			for example, when determining if two URLs refer to the same resource clients
			need to compare the canonical URLs not the URLs used to access the resources.
	</div>
	<div id="ldpr-4_1_5" class="rule">4.1.5 LDPRs SHOULD reuse existing vocabularies instead of creating
		their own duplicate vocabulary terms.  In addition to this general rule, some specific cases are
		covered by other conformance rules.
	</div>
	<div id="ldpr-4_1_5_1" class="rule">4.1.5.1 LDPR predicates SHOULD use standard vocabularies such as Dublin Core
		[[!DC-TERMS]], RDF [[!RDF-PRIMER]] and RDF Schema [[!RDF-SCHEMA]], whenever
		possible.
	</div>
	<div id="ldpr-4_1_6" class="rule">4.1.6 LDPRs MUST use the predicate <code>rdf:type</code> to
		represent the concept of type. The use of non-standard type
		predicates, as well as <code>dcterms:type</code>, is
		discouraged (see <a href="#ldpr-prop">4.8 Common Properties</a>), as it is not recommended
		by the Dublin Core Metadata Initiative for use with RDF resources [[!DC-RDF]]. 
	</div>
	<div id="ldpr-4_1_7" class="rule">4.1.7 LDPR representations SHOULD have at least one <code>rdf:type</code>
		set explicitly.  This makes the representations much more useful to
		client applications that don’t support inferencing.
	</div>
	<div id="ldpr-4_1_8" class="rule">4.1.8 Predicate URIs used in LDPR representations SHOULD be HTTP URLs.
		 These predicate URIs MUST identify LDPRs whose representations are
		retrievable. LDPR servers SHOULD provide an RDF Schema [[!RDF-SCHEMA]]
		representation of these predicates.
		
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/9">ISSUE-9</a></div>
	Should properties used in LDPR representations be LDPRs?
	</div>
	</div>

	<div id="ldpr-4_1_9" class="rule">4.1.9 LDPRs MUST use at least one RDF triple to represent a link
		(relationship) to another resource. In other words, having the source
		resource’s URI as the subject and the target resource’s URI as the
		object of the triple representing the link (relationship) is enough and
		does not require the creation of an intermediate link resource to
		describe the relationship.
	</div>
	<div id="ldpr-4_1_10" class="rule">4.1.10 LDPR servers MAY support standard representations beyond those
		necessary to conform to this specification. These
		could be other RDF formats, like N3 or NTriples, but non-RDF formats
		like HTML [[!HTML401]] and JSON [[!RFC4627]] would be likely be common.
		
	<div id="ldpr-4_1_11" class="rule">4.1.11 LDPRs MAY be created, updated and deleted using methods not defined in
		this document, for example through application-specific means, SPARQL
		UPDATE, etc. [[!SPARQL-UPDATE]], as long as those methods do not conflict with this specification's 
		normative requirements.
	</div>
	<div id="ldpr-4_1_12" class="rule">4.1.12 LDPR server responses MUST contain accurate response <code>ETag</code>
		header values.
	</div>
		
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/10">ISSUE-10</a></div>
	Include clarifications and guidance around ETags
	</div>
	</div>
	
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/15">ISSUE-15</a></div>
	sharing binary resources and metadata
	</div>
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/16">ISSUE-16</a></div>
	Redirection of non-information resources to LDPRs
	</div>
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/19">ISSUE-19</a></div>
	Adressing more error cases
	</div>	
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/32">ISSUE-32</a></div>
	How can clients discover that a resource is an LDPR or LDPC, and what features are supported?
	</div>
		<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/33">ISSUE-33</a></div>
	Pagination for non-container resources
	</div>

	<div id="ldpr-4_1_13" class="rule">4.1.13 LDPR
		servers SHOULD enable simple creation and modification of LDPRs.
		It is
		common for LDPR servers to put restrictions on representations – for
		example, the range of <code>rdf:type</code> predicates, datatypes of
		the objects of predicates, and the number of occurrences of predicates in an LDPR, but
		servers SHOULD minimize those restrictions.  Enforcement of
		more complex constraints will greatly restrict the set of clients
		that can modify resources. For some server applications, excessive
		constraints on modification of resources may be required.
	</div>
</section>

<section>
<h2 id="ldpr-HTTP_GET">HTTP GET</h2>
	<div id="ldpr-4_2_1" class="rule">4.2.1 LDPR servers MUST support the HTTP GET Method for LDPRs.
	</div>
	<div id="ldpr-4_2_2" class="rule">4.2.2 LDPR servers MUST provide a <code>text/turtle</code>
		representation of the requested LDPR [[!TURTLE]].
	</div>
	<div id="ldpr-4_2_3" class="rule">4.2.3 LDPR servers MAY provide 
		representations of the requested LDPR beyond those
		necessary to conform to this specification, using standard HTTP content negotiation. 
		If the client does not indicate a preference, <code>text/turtle</code> MUST be returned.
		
	<div id="ldpr-4_2_4" class="rule">4.2.4 In the absence of special knowledge of the application or domain, LDPR
		clients MUST assume that any LDPR can have multiple values for <code>rdf:type</code>.
	</div>
	<div id="ldpr-4_2_5" class="rule">4.2.5 In the absence of special knowledge of the application or domain, LDPR
		clients MUST assume that the <code>rdf:type</code> values
		of a given LDPR can change over time.
	</div>
</section>

<section>
<h2 id="ldpr-HTTP_POST">HTTP POST</h2>
	<p>This specification adds no new requirements on HTTP POST for LDPRs.</p>
</section>

<section>
<h2 id="ldpr-HTTP_PUT">HTTP PUT</h2>
	<p>This specification imposes the following new requirements on HTTP PUT for LDPRs 
		only when the LDPR supports that method.  This specification does not impose any
		new requirement to support that method, and [[!HTTP11]] makes it optional.</p>
		
	<div id="ldpr-4_4_1" class="rule">4.4.1 If HTTP PUT is performed on an existing resource, LDPR servers MUST
		replace the entire persistent state of the identified resource with
		the entity representation in the body of the request. The only
		recognized exception are the properties <code>dcterms:modified</code>
		and <code>dcterms:creator</code> that are never under
		client control - LDPR servers MUST ignore any values of these
		properties that are provided by the client. Any LDPR servers that wish
		to support a more sophisticated merge of data provided by the client
		with existing state stored on the server for a resource MUST use HTTP
		PATCH, not HTTP PUT.
		
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/11">ISSUE-11</a></div>
	Do we need to define server-managed properties or do we leave them to applications?
	</div>
	</div>
	<div id="ldpr-4_4_2" class="rule">4.4.2 LDPR clients SHOULD use the HTTP <code>If-Match</code>
		header and HTTP <code>ETags</code> to ensure it isn’t
		modifying a resource that has changed since the client last retrieved
		its representation. LDPR servers SHOULD require the HTTP <code>If-Match</code> header and HTTP <code>ETags</code>
		to detect collisions. LDPR servers MUST respond with status code 412
		(Condition Failed) if <code>ETag</code>s fail to match if there are no other
		errors with the request [[!HTTP11]].
	</div>
	<div id="ldpr-4_4_3" class="rule">4.4.3 LDPR clients SHOULD always assume that the set of predicates for a
		resource of a particular type at an arbitrary server is open, in the
		sense that different resources of the same type may not all have the
		same set of predicates in their triples, and the set of predicates that
		are used in the state of any one resource is not limited to any pre-defined
		set.
	</div>
	<div id="ldpr-4_4_4" class="rule">4.4.4 LDPR clients SHOULD assume that a LDPR server could discard triples
		whose predicates the server does not recognize or otherwise chooses
		not to persist. In other words, LDPR servers MAY restrict themselves
		to a known set of predicates, but LDPR clients MUST NOT restrict themselves to a known set of predicates 
		when their intent is to perform a later HTTP PUT to update the resource.
	</div>
	<div id="ldpr-4_4_5" class="rule">4.4.5 A LDPR client MUST preserve all triples retrieved using HTTP GET that
		it doesn’t change whether it understands the predicates or not, when
		its intent is to perform an update using HTTP PUT.  The use of HTTP
		PATCH instead of HTTP PUT for update avoids this burden for clients
		[[RFC5789]].
	</div>
	<div id="ldpr-4_4_6" class="rule">4.4.6 LDPR servers MAY choose to allow the creation of new resources using HTTP PUT.
	</div>
	<div id="ldpr-4_4_7" class="rule">4.4.7 LDPR servers SHOULD allow clients to update resources without
		requiring detailed knowledge of server-specific constraints.  
		This is a consequence of the requirement to <a href="#ldpr-4_1_13">enable simple creation and modification</a> of LPDRs.
	</div>		
</section>
		
<section>
<h2 id="ldpr-HTTP_DELETE">HTTP DELETE</h2>
	<p>This specification imposes the following new requirements on HTTP DELETE for LDPRs 
		only when the LDPR supports that method.  This specification does not impose any
		new requirement to support that method, and [[!HTTP11]] makes it optional.</p>
		
	<div id="ldpr-4_5_1" class="rule">4.5.1 LDPR servers MUST remove the resource identified by the Request-URI.
		After a successful HTTP DELETE, a subsequent HTTP GET on the same
		Request-URI MUST result in a 404 (Not found) or 410 (Gone) status
		code. Clients SHOULD note that servers MAY reuse a URI under some circumstances.
	</div>
	
	<div id="ldpr-4_5_2" class="rule">4.5.2 LDPR servers MAY alter the state of other resources as a result of an
		HTTP DELETE request. For example, it is acceptable for the server to
		remove triples from other resources whose subject or object is the
		deleted resource. It is also acceptable and common for LDPR servers to
		not do this – behavior is server application specific.
	</div>
</section>

<section>
<h2 id="ldpr-HTTP_HEAD">HTTP HEAD</h2>
	<div id="ldpr-4_6_1" class="rule">4.6.1 LDPR servers MUST support the HTTP HEAD method.</div>
	<div id="ldpr-4_6_2" class="rule">4.6.2 LDPR servers MUST indicate their support for HTTP Methods by
		responding to a HTTP HEAD request on the LDPR’s URL with the HTTP
		Method tokens in the HTTP response header “<code>Allow</code>”.
	</div>
</section>

<section>
<h2 id="ldpr-HTTP_PATCH">HTTP PATCH</h2>
	<p>This specification imposes the following new requirements on HTTP PATCH for LDPRs 
		only when the LDPR supports that method.  This specification does not impose any
		new requirement to support that method, and [[!HTTP11]] makes it optional.</p>
		
	<div id="ldpr-4_7_1" class="rule">4.7.1 LDPR servers MAY implement HTTP PATCH to allow modifications,
		especially partial replacement, of their resources [[!RFC5789]]. No
		minimal set of patch document formats is mandated by this document.
	</div>
	<div id="ldpr-4_7_2" class="rule">4.7.2 LDPR servers SHOULD allow clients to update resources without
		requiring detailed knowledge of server-specific constraints.  
		This is a consequence of the requirement to <a href="#ldpr-4_1_13">enable simple creation and modification</a> of LPDRs.
	</div>
	<div id="ldpr-4_7_3" class="rule">4.7.3 LDPR servers SHOULD NOT allow clients to create new resources using PATCH.
		<a href="#ldpr-5_4">POST (to a LDPC)</a> and/or <a href="#ldpr-4_4">PUT</a> should be used as the standard way to create new LDPRs.
	</div>
	
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/12">ISSUE-12</a></div>
	Can HTTP PATCH be used for resource creation?
	2012-12-17 WG mtg: resolved as Discouraged - 4.7.3 added for review.
	</div>
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/17">ISSUE-17</a></div>
	changesets as a recommended PATCH format
	</div>		
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/27">ISSUE-27</a></div>
	Should the PATCH method be used, as opposed to POST with a given mime type?
	</div>
</section>

<section>
<h2 id="ldpr-prop">Common Properties</h2>
	<p>
		This section summarizes some well-known RDF vocabularies that MUST be
		used in Linked Data Platform Resources wherever a resource needs to use a
		predicate whose meaning matches one of these. For example, if an LDPR
		 has a <em>description</em>, and the application semantic of that
		<em>description</em> is compatible with <code>dcterms:description</code>,
		then <code>dcterms:description</code> MUST be used. If
		needed, additional application-specific predicates MAY be used. A
		specification based on <abbr title="Linked Data Platform">LDP</abbr> may require one or
		more of these properties for a particular resource type. The Range
		column in the tables below identifies the RECOMMENDED <code>rdfs:range</code>
		for the properties.
	</p>
	<div id="ldpr-4_8_1" class="rule">4.8.1 From Dublin Core</div>
	<p>
		URI: <code>http://purl.org/dc/terms/</code>
	</p>
	<table border="1" cellspacing="5" summary="Dublin Core properties recommended">
		<tr>
			<td>Property</td>
			<td>Range/DataType</td>
			<td>Comment</td>
		</tr>
		<tr>
			<td><code>dcterms:contributor</code></td>
			<td><code>dcterms:Agent</code></td>
			<td></td>
		</tr>
		<tr>
			<td><code>dcterms:creator</code></td>
			<td><code>dcterms:Agent</code></td>
			<td></td>
		</tr>
		<tr>
			<td><code>dcterms:created</code></td>
			<td><code>xsd:dateTime</code></td>
			<td></td>
		</tr>
		<tr>
			<td><code>dcterms:description</code></td>
			<td><code>rdf:XMLLiteral</code></td>
			<td>
					Descriptive text about the resource represented as rich text in
					XHTML format. SHOULD include only content that is valid and suitable inside an XHTML
					<code>&lt;div&gt;</code> element.
			</td>
		</tr>
		<tr>
			<td><code>dcterms:identifier</code></td>
			<td><code>rdfs:Literal</code></td>
			<td></td>
		</tr>
		<tr>
			<td><code>dcterms:modified</code></td>
			<td><code>xsd:dateTime</code></td>
			<td></td>
		</tr>
		<tr>
			<td><code>dcterms:relation</code></td>
			<td><code>rdfs:Resource</code></td>
			<td>The HTTP URI of a related resource. This is the
					predicate to use when you don't know what else to use. If you know
					more specifically what sort of relationship it is, use a more
					specific predicate.</td>
		</tr>
		<tr>
			<td><code>dcterms:subject</code></td>
			<td><code>rdfs:Resource</code></td>
			<td></td>
		</tr>
		<tr>
			<td><code>dcterms:title</code></td>
			<td><code>rdf:XMLLiteral</code></td>
			<td>A name given to the resource. Represented as rich text in XHTML
					format. SHOULD include only content that is valid inside an XHTML <code>&lt;span&gt;</code>
					element.</td>
		</tr>
	</table>

	<div id="ldpr-4_8_1_1" class="rule">4.8.1.1 From Dublin Core
	<p>
		The predicate <code>dcterms:type</code> SHOULD NOT be
		used in LDPRs, instead use <code>rdf:type</code> [[!DC-RDF]].
		See also <a href="#ldpr-4_1_6">4.1.6 LDPRs MUST use <code>rdf:type</code></a>.
	</p>
	</div>
	
	<div id="ldpr-4_8_2" class="rule">4.8.2 From RDF</div>
	<p>
		URI: <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#</code>
	</p>
	<table border="1" cellspacing="5" summary="RDF properties recommended">
		<tr>
			<td>Property</td>
			<td>Range</td>
			<td>Comment</td>
		</tr>
		<tr>
			<td><code>rdf:type</code></td>
			<td><code>rdfs:Class</code></td>
			<td>The type or types of the resource</td>
		</tr>
	</table>
	
	<div id="ldpr-4_8_3" class="rule">4.8.3 From RDF Schema</div>
	<p>
		URI: <code>http://www.w3.org/2000/01/rdf-schema#</code>
	</p>
	
	
	<table border="1" cellspacing="5" summary="RDF Schema properties recommended">
		<tr>
			<td>Property</td>
			<td>Range</td>
			<td>Comment</td>
		</tr>
		<tr>
			<td><code>rdfs:member</code></td>
			<td><code>rdfs:Resource</code></td>
			<td></td>
		</tr>
		<tr>
			<td><code>rdfs:label</code></td>
			<td><code>rdfs:Literal</code></td>
			<td>Only use this in vocabulary documents, to define
					the name of the vocabulary term.</td>
		</tr>
	</table>		
</section>
</section>

<section>
<h1 id="ldpc">Linked Data Platform Containers</h1>

<section class="informative">		
<h2 id="ldpc-informative">Informative</h2>
	<p>Many HTTP applications and sites have organizing
		concepts that partition the overall space of resources into smaller
		containers. Blog posts are grouped into blogs, wiki pages are grouped
		into wikis, and products are grouped into catalogs. Each resource
		created in the application or site is created within an instance of
		one of these container-like entities, and users can list the existing
		artifacts within one. Containers answer some basic questions, which
		are:</p>
	<ol>
		<li>To which URLs can I POST to create new resources?</li>
		<li>Where can I GET a list of existing resources?</li>
		<li>How	is the order of the container entries expressed?</li>
		<li>How do I get information about the members along with the container?</li>
		<li>How	do I GET the entries of a large container broken up into pages?</li>
		<li>How	can I ensure the resource data is easy to query?</li>
	</ol>
	<p>
		This document defines the representation and behavior of containers
		that address these issues. The set of members of a container is
		defined by a set of triples in its representation (and state) called
		the membership triples. The membership triples of a container all
		have the same subject and predicate – the objects of the membership
		triples define the members of the container. The subject of the
		membership triples is called the membership subject and the predicate
		is called the membership predicate. In the simplest cases, the
		membership subject will be the LDPC resource itself, but it does not
		have to be. The membership predicate is also variable and will often
		be a predicate from the server application vocabulary or the <code>rdfs:member</code> predicate.
	</p>
	<p>This document includes a set of guidelines for
		using POST to create new resources and add them to the list of
		members of a container. This document also explains how to include
		information about each member in the container’s own representation
		and how to paginate the container representation if it gets too big.</p>
	<p>The model for containers follow that of strong composition.  Due to composition
	   constraints, the lifespan of the member resource must match that of its container and it a member resource 
	   can not be a member of more than one container. Members are 
	   only added by using POST, which both creates the resource and inserts a membership triple.
	   A request to delete a container that has members, will result in all 
	   the members and the container itself will be deleted. A member resource is removed
	   from a container by deleting the resource directly, which removes the
	   membership triple from the container.</p>
	<p>The following illustrates a very simple
		container with only three members and some information about the
		container (the fact that it is a container and a brief title):</p>

<pre class="example"># The following is the representation of
#    http://example.org/container1
@prefix dcterms: &lt;http://purl.org/dc/terms/&gt;.
@prefix rdfs: &lt;http://www.w3.org/2000/01/rdf-schema#&gt;.
@prefix ldp: &lt;http://www.w3.org/ns/ldp#&gt;.

&lt;http://example.org/container1&gt;
   a ldp:Container;
   dcterms:title "A very simple container";
   rdfs:member
      &lt;http://example.org/container1/member1&gt;,
      &lt;http://example.org/container1/member2&gt;,
      &lt;http://example.org/container1/member3&gt;.</pre>

	<p>This example is very straightforward - the
			membership predicate is <code>rdfs:member</code> and the membership subject is the container
			itself. A POST to this container will create a new resource
			and add it to the list of members by adding a new membership triple
			to the container.</p>

	<p>Sometimes it is useful to use a subject
			other than the container itself as the membership subject and to use
			a predicate other than <code>rdfs:member</code> as the membership predicate, as illustrated
			below.</p>

<pre class="example" id="ldpc-ex-membership-subj">
# The following is the representation of
#   http://example.org/netWorth/nw1/assetContainer
@prefix rdfs: &lt;http://www.w3.org/2000/01/rdf-schema#&gt;.
@prefix ldp: &lt;http://www.w3.org/ns/ldp#&gt;.
@prefix o: &lt;http://example.org/ontology/&gt;.

&lt;http://example.org/netWorth/nw1/assetContainer&gt;
   a ldp:Container;
   ldp:membershipSubject &lt;http://example.org/netWorth/nw1&gt;;
   ldp:membershipPredicate o:asset.

&lt;http://example.org/netWorth/nw1&gt;
   a o:NetWorth;
   o:asset
      &lt;http://example.org/netWorth/nw1/assetContainer/a1&gt;,
      &lt;http://example.org/netWorth/nw1/assetContainer/a2&gt;.</pre>

	<p>
		The essential structure of the container is
		the same, but in this example, the membership subject is not the
		container itself – it is a separate net worth resource. The
		membership predicate is <code>o:asset</code> – a predicate from the domain model. A POST to
		this container will create a new asset and add it to the list of
		members by adding a new membership triple to the container. You
		might wonder why we didn’t just make <code>http://example.org/netWorth/nw1</code> a container and POST
		the new asset directly there. That would be a fine design if <code>http://example.org/netWorth/nw1</code> had only assets, but if it has separate
		predicates for assets and liabilities, that design will not work
		because it is unspecified to which predicate the POST should add a
		membership triple. Having separate <code>http://example.org/netWorth/nw1/assetContainer</code> and <code>http://example.org/netWorth/nw1/liabilityContainer</code> container resources allows both assets and
		liabilities to be created.
	</p>
	<p>In this example, clients cannot simply guess
			which resource is the membership subject and which predicate is the
			membership predicate, so the example includes this information in
			triples whose subject is the LDPC resource itself.
	</p>
	
	<div id="ldpc-member_data" class="rule">5.1.1 Container Member Information</div>
	<em>This section is non-normative</em>
	<p>In many – perhaps most – applications
		involving containers, it is desirable for the client to be able to
		get information about each container member without having to do a
		GET on each one. LDPC allows servers to include this information
		directly in the representation of the container. The server decides
		the amount of data about each member that is provided. Some common
		strategies include providing a fixed number of standard properties,
		or providing the entire RDF representation of each member resource,
		or providing nothing. The server application domain and its use-cases
		will determine how much information is required.</p>

	<p>Continuing on from the net worth
		example, there will be additional triples for the member resources
		(assets) in the representation:</p>

<pre class="example"># The following is the representation of
#	 http://example.org/netWorth/nw1/assetContainer
@prefix dcterms: &lt;http://purl.org/dc/terms/&gt;.
@prefix rdfs:    &lt;http://www.w3.org/2000/01/rdf-schema#&gt;.
@prefix ldp:      &lt;http://www.w3.org/ns/ldp#&gt;.
@prefix o:       &lt;http://example.org/ontology/&gt;.

&lt;http://example.org/netWorth/nw1/assetContainer&gt;
   a ldp:Container;
   dcterms:title "The assets of JohnZSmith";
   ldp:membershipSubject &lt;http://example.org/netWorth/nw1&gt;;
   ldp:membershipPredicate o:asset.

&lt;http://example.org/netWorth/nw1&gt;
   a o:NetWorth;
   o:asset
      &lt;http://example.org/netWorth/nw1/assetContainer/a1&gt;,
      &lt;http://example.org/netWorth/nw1/assetContainer/a3&gt;,
      &lt;http://example.org/netWorth/nw1/assetContainer/a2&gt;.

&lt;http://example.org/netWorth/nw1/assetContainer/a1&gt;
   a o:Stock;
   o:value 10000.
&lt;http://example.org/netWorth/nw1/assetContainer/a2&gt;
   a o:Bond;
   o:value 20000.
&lt;http://example.org/netWorth/nw1/assetContainer/a3&gt;
   a o:RealEstateHolding;
   o:value 300000.</pre>

	<div id="ldpc-get_non-member_props" class="rule">5.1.2 Retrieving Only Non-member Properties
	</div>
	<em>This section is non-normative</em>
	<p>The representation of a container
		that has many members will be large. There are several important
		cases where clients need to access only the non-member properties of
		the container. Since retrieving the whole container representation to
		get this information may be onerous for clients and cause unnecessary
		overhead on servers, it is desired to define a way to retrieve only
		the non-member property values. Defining for each LDPC a corresponding
		resource, called the “non-member resource”, whose state is a subset
		of the state of the container, does this.</p>
	<p>The example listed here only show
		a simple case where only a few simple non-member properties are
		retrieved. In real world situations more complex cases are likely, such as those that add other predicates to
		containers, for example providing validation information and
		associating SPARQL endpoints. [[SPARQL-QUERY]]</p>
	<p>
		Here is an example requesting the non-member properties of a
		container identified by the URL <code>http://example.org/container1</code>
		and adding the query string <code>?non-member-properties</code> :
	</p>
<p>Request:</p>
<pre class="example">GET /container1?non-member-properties HTTP/1.1
Host: example.org
Accept: text/turtle; charset=UTF-8
</pre>
<p>Response:</p>
<pre class="example">HTTP/1.1 200 OK
Content-Type: text/turtle; charset=UTF-8
ETag: "_87e52ce291112"
Content-Length: 325

@prefix rdfs: &lt;http://www.w3.org/2000/01/rdf-schema#&gt;.
@prefix dcterms: &lt;http://purl.org/dc/terms/&gt;.
@prefix ldp: &lt;http://www.w3.org/ns/ldp#&gt;.

&lt;http://example.org/container1&gt;
   a ldp:Container;
   dcterms:title "A Linked Data Platform Container of Acme Resources";
   ldp:membershipPredicate rdfs:member;
   dcterms:publisher &lt;http://acme.com/&gt;.</pre>

	<div id="ldpc-paging" class="rule">5.1.3 Paging</div>
	<em>This section is non-normative</em>
	<p>It sometimes happens that a
		container is too large to reasonably transmit its representation in a
		single HTTP response. This will be especially true if the container
		representation includes many triples from the representations of its
		members. A client may anticipate that a container will be too large -
		for example, a client tool that accesses defects may assume that an
		individual defect will usually be of sufficiently constrained size
		that it makes sense to request all of it at once, but that the
		container of all the defects ever created will typically be too big.
		Alternatively, a server may recognize that a container that has been
		requested is too big to return in a single message.</p>
	<p>
		To address this problem, LDPCs may support a technique called Paging.  Paging can be achieved with a
		simple RDF pattern. For each container resource, <code>&lt;containerURL&gt;</code>, we define a new
		resource <code>&lt;containerURL&gt;?firstPage</code>.
		The triples in the representation of <code>&lt;containerURL&gt;?firstPage</code>
		are a subset of the triples in <code>&lt;containerURL&gt;</code>
		- same subject, predicate and object.
	</p>
	<p>LDPC servers may respond to requests for a
		container by redirecting the client to the first page resource –
		using a 303 “See Other” redirect to the actual URL for the page
		resource.</p>
	<p>
		Continuing on from the member information from the JohnZSmith net
		worth example, we’ll split the response across two pages.  The client
		requests the first page as <code>http://example.org/netWorth/nw1/assetContainer?firstPage</code>:
	</p>
<pre class="example"># The following is the representation of
#    http://example.org/netWorth/nw1/assetContainer?firstPage
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt;.
@prefix dcterms: &lt;http://purl.org/dc/terms/&gt;.
@prefix ldp: &lt;http://www.w3.org/ns/ldp#&gt;.
@prefix o: &lt;http://example.org/ontology/&gt;.

&lt;http://example.org/netWorth/nw1/assetContainer&gt;
   a ldp:Container;
   dcterms:title "The assets of JohnZSmith";
   ldp:membershipSubject &lt;http://example.org/netWorth/nw1&gt;;
   ldp:membershipPredicate o:asset.

&lt;http://example.org/netWorth/nw1/assetContainer?firstPage&gt;
   a ldp:Page;
   ldp:pageOf &lt;http://example.org/netWorth/nw1/assetContainer&gt;;
   ldp:nextPage &lt;http://example.org/netWorth/nw1/assetContainer?p=2&gt;.
 
&lt;http://example.org/netWorth/nw1&gt;
    a o:NetWorth;
	o:asset
	&lt;http://example.org/netWorth/nw1/assetContainer/a1&gt;,
	&lt;http://example.org/netWorth/nw1/assetContainer/a4&gt;,
	&lt;http://example.org/netWorth/nw1/assetContainer/a3&gt;,
	&lt;http://example.org/netWorth/nw1/assetContainer/a2&gt;.

&lt;http://example.org/netWorth/nw1/assetContainer/a1&gt;
   a o:Stock;
   o:value 100.00.
&lt;http://example.org/netWorth/nw1/assetContainer/a2&gt;
   a o:Cash;
   o:value 50.00.
# server initially supplied no data for a3 and a4 in this response</pre>

	<p>
		The following example is the result of retrieving the representation
		for the next page:
	</p>

<pre class="example"># The following is the representation of
#  http://example.org/netWorth/nw1/assetContainer?p=2
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt;.
@prefix dcterms: &lt;http://purl.org/dc/terms/&gt;.
@prefix ldp: &lt;http://www.w3.org/ns/ldp#&gt;.
@prefix o: &lt;http://example.org/ontology/&gt;.

&lt;http://example.org/netWorth/nw1/assetContainer&gt;
   a ldp:Container;
   dcterms:title "The assets of JohnZSmith";
   ldp:membershipSubject &lt;http://example.org/netWorth/nw1&gt;;
   ldp:membershipPredicate o:asset.

&lt;http://example.org/netWorth/nw1/assetContainer?p=2&gt;
   a ldp:Page;
   ldp:pageOf &lt;http://example.org/netWorth/nw1/assetContainer&gt;;
   ldp:nextPage rdf:nil.

&lt;http://example.org/netWorth/nw1&gt;
   a o:NetWorth;
   o:asset 
      &lt;http://example.org/netWorth/nw1/assetContainer/a5&gt;.

&lt;http://example.org/netWorth/nw1/assetContainer/a5&gt;
   a o:Stock;
   dcterms:title "Big Co.";
   o:value 200.02.</pre>

	<p>
		In this example, there is only one member in the container in the
		final page.  To indicate this is the last page, a value of <code>rdf:nil</code> is used for the <code>ldp:nextPage</code>
		predicate of the page resource.
	</p>
	<p>LDPC guarantees that any and all the triples
		about the members will be on the same page as the membership triple
		for the member.</p>
		
	<div id="ldpc-ordering" class="rule">5.1.4 Ordering</div>
	<em>This section is non-normative</em>
	<p>
		There are many cases where an ordering of the members of the
		container is important. LDPC does not provide any particular support
		for server ordering of members in containers, because any client can
		order the members in any way it chooses based on the value of any
		available property of the members. In the example below, the value of
		the <code>o:value</code> predicate is present for each
		member, so the client can easily order the members according to the
		value of that property. In this way, LDPC avoids the use of RDF
		constructs like Seq and List for expressing order.
	</p>
	<p>
		Order only becomes important for LDPC servers when containers are
		paginated. If the server does not respect ordering when constructing
		pages, the client is forced to retrieve all pages before
		sorting the members, which would defeat the purpose of pagination. In
		cases where ordering is important, a LDPC server exposes all the
		members on a page with a higher sort order than all members on the
		previous page and lower sort order than all the members on the next
		page. The LDPC specification provides a predicate - <code>ldp:containerSortPredicates</code>
		- that the server may use to communicate to the client which
		predicates were used for page ordering. Multiple predicate values may
		have been used for sorting, so the value of this predicate is an
		ordered list.
	</p>
	<p>Here is an example container described
		previously, with representation for ordering of the assets:</p>
<pre class="example"># The following is the ordered representation of
#   http://example.org/netWorth/nw1/assetContainer
@prefix rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt;.
@prefix dcterms: &lt;http://purl.org/dc/terms/&gt;.
@prefix ldp: &lt;http://www.w3.org/ns/ldp#&gt;.
@prefix o: &lt;http://example.org/ontology/&gt;.

&lt;http://example.org/netWorth/nw1/assetContainer&gt;
   a ldp:Container;
   dcterms:title "The assets of JohnZSmith";
   ldp:membershipSubject &lt;http://example.org/netWorth/nw1&gt;;
   ldp:membershipPredicate o:asset.

&lt;http://example.org/netWorth/nw1/assetContainer?firstPage&gt;
   a ldp:Page;
   ldp:pageOf &lt;http://example.org/netWorth/nw1/assetContainer&gt;;
   ldp:containerSortPredicates (o:value).

&lt;http://example.org/netWorth/nw1&gt;
   a o:NetWorth;
   o:asset
      &lt;http://example.org/netWorth/nw1/assetContainer/a1&gt;,
      &lt;http://example.org/netWorth/nw1/assetContainer/a3&gt;,
      &lt;http://example.org/netWorth/nw1/assetContainer/a2&gt;.

&lt;http://example.org/netWorth/nw1/assetContainer/a1&gt;
   a o:Stock;
   o:value 100.00.
&lt;http://example.org/netWorth/nw1/assetContainer/a2&gt;
   a o:Cash;
   o:value 50.00.
&lt;http://example.org/netWorth/nw1/assetContainer/a3&gt;
   a o:RealEstateHolding;
   o:value 300000.</pre>
		<p>
			As you can see by the addition of the <code>ldp:containerSortPredicates</code> 
			predicate, the <code>o:value</code> predicate is used
			to define the ordering of the results.  It is up to the domain model
			and server to determine the appropriate predicate to indicate the
			resource’s order within a page, and up to the client receiving this 
			representation to use that order in whatever way is appropriate, for 
			example to sort the data prior to presentation on a user interface.
		</p>
</section>

<section>
<h2 id="ldpc-general">General</h2>
	<p>The Linked Data Platform does not define how clients
		discover <dfn><abbr title="Linked Data Platform Containers">LDPCs</abbr></dfn>.</p>

	<div id="ldpc-5_2_1" class="rule">5.2.1 LDPC servers MUST also be conformant LDPR servers. A Linked Data Platform
		Container MUST also be a conformant Linked Data Platform Resource.
	</div>
	<div id="ldpc-5_2_2" class="rule">5.2.2 The same resource, identified by its canonical URI, MUST be a member of 
	only a single LDPC. The same resource can not be a member of mutliple LDPCs.</div>
	<div id="ldpc-5_2_3" class="rule">5.2.3 The state of a LDPC includes information about which
		resources are its members. In the simplest cases, the membership subject
		will be the LDPC resource itself, but it does not have to be. The
		membership predicate is also variable and will often be a predicate
		from the server application vocabulary. If there is no obvious
		predicate from the server application vocabulary to use, LDPC servers
		SHOULD use the <code>rdfs:member</code> predicate.
		
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/21">ISSUE-21</a></div>
	container affordances
	</div>	
	</div>
	<div id="ldpc-5_2_4" class="rule">5.2.4 A LDPC MUST contain one triple containing the <code>ldp:membershipSubject</code>
		predicate when the membership subject is not the LDPC itself.  
		This triple's object provides clients with the LDPC's membership subject URI.
	</div>
	<div id="ldpc-5_2_5" class="rule">5.2.5 A LDPC MUST contain one triple containing the <code>ldp:membershipPredicate</code>
		predicate when
		the container predicate is not <code>rdfs:member</code>.
		This triple's object provides clients with the LDPC's membership predicate URI.
	</div>
	<div id="ldpc-5_2_6" class="rule">5.2.6 The representation of a LDPC MAY include an arbitrary number of
		additional triples whose subjects are the members of the container,
		or that are from the representations of the members (if they have RDF
		representations). This allows a LDPC server to provide clients with
		information about the members without the client having to do a GET
		on each member individually.  See section <a href="#ldpc-member_data">5.1.1 Container
		Member Information</a> for additional details.
		
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/13">ISSUE-13</a></div>
	Include clarifications about LDPC representations that include member triples
	</div>
	</div>
	<div id="ldpc-5_2_7" class="rule">5.2.7 The representation of a LDPC MUST have <code>rdf:type</code>
		of <code>ldp:Container</code>, but it MAY have additional
		<code>rdf:type</code>s.
	</div>
	<div id="ldpc-5_2_8" class="rule">5.2.8 LDPCs SHOULD NOT use RDF container types <code>rdf:Bag</code>,
		<code>rdf:Seq</code> or <code>rdf:List</code>.
	</div>
	
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/34">ISSUE-34</a></div>
	Adding and removing arcs in weak aggregation
	</div>
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/36">ISSUE-36</a></div>
	Can applications create new containers?
	</div>
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/38">ISSUE-38</a></div>
	filtered representations and inlining
	</div>	
</section>

<section>	
<h2 id="ldpc-HTTP_GET">HTTP GET</h2>
	<div id="ldpc-5_3_1" class="rule">5.3.1 The representation of a LDPC MUST contain a set of triples with a
		consistent subject and predicate whose objects indicate members of
		the container. The subject of the triples MAY be the container itself
		or MAY be another resource (as in the <a href="#ldpc-ex-membership-subj">example</a>).  See also
		<a href="#ldpc-5_2_3">5.2.3</a>.
	</div>
	<div id="ldpc-5_3_2" class="rule">5.3.2 LDPC servers SHOULD support requests for information about a known LDPC
		without retrieving a full representation including all of its
		members, by the existence of the token "<code>non-member-properties</code>" on the query
		component of the LDPC URL.  For example, if there is a LDPC URL <code>&lt;containerURL&gt;,</code> the URL to request the
		non-membership properties would be <code>&lt;containerURL&gt;?non-member-properties</code>.
		 See section <a href="#ldpc-get_non_member_props">5.1.2 Retrieving Non-member Properties</a> for
		additional details. A LDPC server that does not support a request to
		retrieve non-member resource properties via a Request-URI of “<code>&lt;containerURL&gt;?non-member-properties</code>”,
		MUST return a HTTP status code 404 (Not Found).  A LDPC server that supports a request to
		retrieve non-member resource properties via a different Request-URI than “<code>&lt;containerURL&gt;?non-member-properties</code>”,
		MUST return a HTTP Redirection 3xx status code such as 301 (Moved Permanently) or 302 (Found).
	</div>
	<div id="ldpc-5_3_3" class="rule">5.3.3 A LDPC server that does not support a request to retrieve the first
		page resource representation from a known LDPC whose URL is “<code>&lt;containerURL&gt;</code>” by using
		the Request-URI “<code>&lt;containerURL&gt;?firstPage</code>”, MUST return a HTTP status code 404 (Not
		Found).
		A LDPC server that supports that request using a different Request-URI than “<code>&lt;containerURL&gt;?firstPage</code>”,
		MUST return a HTTP Redirection 3xx status code such as 301 (Moved Permanently) or 302 (Found).
	</div>
	<div id="ldpc-5_3_4" class="rule">5.3.4 LDPC servers SHOULD support requests for splitting large LDPCs into
		pages indicated by a client supplying the token “<code>firstPage</code>”
		on the query component of the LDPC URL. For example, if there is a LDPC
		URL <code>&lt;containerURL&gt;</code>, the URL to request
		the first page would be <code>&lt;containerURL&gt;?firstPage</code>.
		The representation for any page, including the first, will include
		the URL for the next page. See section <a href="#ldpc-paging">5.1.3 titled “Paging”</a> for additional details.
	</div>
	<div id="ldpc-5_3_5" class="rule">5.3.5 LDPC servers MAY split the response representation of a LDPC regardless
		of what the client requested (such as when a client omits a “<code>firstPage</code>”
		query component of a request URL). This is also known as
		server-initiated paging. See section  <a href="#ldpc-paging">5.1.3 Paging</a> for
		additional details.
	</div>
	<div id="ldpc-5_3_5_1" class="rule">5.3.5.1 LDPC servers that initiate paging SHOULD respond to requests for a LDPC
		by redirecting the client to the page resource – using a 303 “See
		Other” redirect to the actual URL for the page resource.
	</div>
	<div id="ldpc-5_3_6" class="rule">5.3.6 LDPC servers that support paging MUST include in the page
		representation a representation for the LDPC, such that:
	</div>
	<div id="ldpc-5_3_6_1" class="rule">5.3.6.1 The page resource representation SHOULD have one triple to indicate its
		type, whose subject is the URL of the page, whose predicate is <code>rdf:type</code> and object is <code>ldp:Page;</code>
		it also SHOULD have 1 triple to indicate the container it is paging,
		whose  subject is the URL of the page, predicate is <code>ldp:pageOf,</code>
		and object is the URL of the LDPC.
	</div>
	<div id="ldpc-5_3_6_2" class="rule">5.3.6.2 The page resource representation MUST have one triple with the subject
		of the page, predicate of <code>ldp:nextPage</code> and
		object being the URL for the subsequent page.
	</div>
	<div id="ldpc-5_3_6_3" class="rule">5.3.6.3 The last page resource representation MUST have one triple with the subject of the 
	    last page, predicate of <code>ldp:nextPage</code> and object being <code>rdf:nil</code>.
	</div>
	
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/18">ISSUE-18</a></div>
	container membership and robust pagination
	</div>	
	
	<div id="ldpc-5_3_7" class="rule">5.3.7 LDPC servers MAY represent the members of a paged LDPC in a sequential
		order.  The order MUST be specified using the <code>ldp:containerSortPredicates</code>
		predicate whose subject is that of the page and object is a list of
		LDPC ordinal predicates.  The default ordering is ascending. The only
		ordinal predicate literal data types supported are those as defined
		by SPARQL SELECT’s ORDER BY clause [[!SPARQL-QUERY]].
		
			<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/14">ISSUE-14</a></div>
	Include clarifications about ordering in LDPC representations
	</div>
	</div>
	<div id="ldpc-5_3_7_1" class="rule">5.3.7.1 The object of <code>ldp:containerSortPredicates</code>,
		the predicate used to indicate ordering, MUST NOT change between
		subsequent pages. If it does, ordering among members of a container
		across pages is undefined. See section <a href="#ldpc-ordering">5.1.4 Ordering</a> for
		additional details.
	</div>
</section>

<section>
<h2 id="ldpc-HTTP_POST">HTTP POST</h2>
	<p>This specification imposes the following new requirements on HTTP POST for LDPCs 
		only when an LDPC supports that method.  This specification does not impose any
		new requirement to support that method, and [[!HTTP11]] makes it optional.</p>
		
	<div id="ldpc-5_4_1" class="rule">5.4.1 LDPC clients SHOULD create member resources by submitting a representation as
		the entity body of the HTTP POST to a known LDPC. LDPC servers MUST
		respond with status code 201 (Created) and the <code>Location</code>
		header set to the new resource’s URL.
	</div>
	<div id="ldpc-5_4_2" class="rule">5.4.2 After a successful HTTP POST request to a LDPC, the new resource MUST
		appear as a member of the LDPC until the new resource is deleted or
		removed by other methods. A LDPC MAY also contain resources that were
		added through other means - for example through the user interface of
		the site that implements the LDPC.
	</div>
	
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/35">ISSUE-35</a></div>
	POSTing to a container MUST yield a fresh URI
	</div>
	
	<div id="ldpc-5_4_3" class="rule">5.4.3 LDPC servers MAY accept an HTTP POST of non-RDF representations for
		creation of any kind of resource, for example binary resources.
	</div>
	<div id="ldpc-5_4_4" class="rule">5.4.4 For servers that support create, LDPC servers MUST create a LDPR from a
		RDF representation in the request entity body.
	</div>
	<div id="ldpc-5_4_5" class="rule">5.4.5 LDPC servers SHOULD NOT include the representation of the created
		resource in the entity body of a 201 (Created) response. In other
		words, clients should not expect any representation in the response
		entity body on a 201 (Created) response.
	</div>
	
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/39">ISSUE-39</a></div>
	HTTP status codes used for creation
	</div>
	
	<div id="ldpc-5_4_6" class="rule">5.4.6 LDPC servers MUST accept a request entity body with a request header
	    of <code>Content-Type</code> with value of <code>text/turtle</code> [[!TURTLE]].
	</div>
	<div id="ldpc-5_4_7" class="rule">5.4.7 LDPC servers SHOULD use the <code>Content-Type</code> request header 
		to determine the representation format when the request has an entity body.  When the header is absent, 
		LDPC servers MAY infer the content type by inspecting the entity body contents [[!HTTP11]].
	</div>
	<div id="ldpc-5_4_8" class="rule">5.4.8 In RDF representations, LDPC servers MUST interpret the null relative
		URI for the subject of triples in the LDPR representation in the
		request entity body as referring to the entity in the request body.
		Commonly, that entity is the model for the “to be created” LDPR, so
		triples whose subject is the null relative URI will usually result in
		triples in the created resource whose subject is the created
		resource.  
		
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/20">ISSUE-20</a></div>
	Identifying and naming POSTed resources
	</div>	
	</div>
	
	<div id="ldpc-5_4_9" class="rule">5.4.9 LDPC servers SHOULD assign the subject URI for the resource to be
		created using server application specific rules.
	</div>
	
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/43">ISSUE-43</a></div>
	hint at naming a resource on creation
	</div>
	
	
	<div id="ldpc-5_4_10" class="rule">5.4.10 LDPC servers SHOULD allow clients to create new resources without
		requiring detailed knowledge of application-specific constraints.
		This is a consequence of the requirement to 
		<a href="#ldpr-4_1_13">enable simple creation and modification</a> of LPDRs.
	</div>
</section>

<section>
<h2 id="ldpc-HTTP_PUT">HTTP PUT</h2>
	<p>This specification imposes the following new requirements on HTTP PUT for LDPCs 
		only when an LDPC supports that method.  This specification does not impose any
		new requirement to support that method, and [[!HTTP11]] makes it optional.</p>
		
	<div id="ldpc-5_5_1" class="rule">5.5.1 LDPC servers SHOULD NOT allow HTTP PUT to update a LDPC’s members and
		if the server receives such a request, it SHOULD respond with a 409
		(Conflict) status code.
	</div>
	<div id="ldpc-5_5_2" class="rule">5.5.2 LDPC servers MAY allow updating LDPC non-membership properties using
		HTTP PUT on <code>&lt;containerURL&gt;?non-member-properties</code>, which
		MAY exclude server-managed properties such as <code>ldp:membershipSubject</code> and <code>ldp:membershipPredicate</code>.
	</div>
</section>

<section>
<h2 id="ldpc-HTTP_DELETE">HTTP DELETE</h2>
	<p>This specification imposes the following new requirements on HTTP DELETE for LDPRs 
		only when a LDPC supports that method.  This specification does not impose any
		new requirement to support that method, and [[!HTTP11]] makes it optional.</p>
		
	<div id="ldpc-5_6_1" class="rule">5.6.1 When a resource that is contained in a LDPC (for example referenced by
		a membership triple) is deleted, the server MUST also remove it from
		the LDPC by removing the membership triple.
	</div>	<div id="ldpc-5_6_2" class="rule">5.6.2 If a LDPC server supports deletion of the LDPC, the server MUST also
		delete the resources that are referenced as its contents.  The LDPC memebership triple MUST also be updated as defined
		by <a href="#ldpc-5_6_1">5.6.1</a> above.
	</div>
	
	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/28">ISSUE-28</a></div>
	transaction/rollback when deleting resources from a LDPC
	</div>

</section>

<section>
<h2 id="ldpc-HTTP_HEAD">HTTP HEAD</h2>
	<p>There are no additional requirements on HTTP
		HEAD.</p>
</section>

<section>
<h2 id="ldpc-HTTP_PATCH">HTTP PATCH</h2>
	<p>This specification imposes the following new requirements on HTTP PATCH for LDPCs 
		only when a LDPC supports that method.  This specification does not impose any
		new requirement to support that method, and [[!HTTP11]] makes it optional.</p>
		
	<div id="ldpc-5_8_1" class="rule">5.8.1 LDPC servers are RECOMMENDED to support HTTP PATCH as the preferred
		method for updating LDPC non-membership properties.
	</div>
</section>

	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/7">ISSUE-7</a></div>
	What operations are permitted on containers and how do they get invoked?
	</div>
</section>

<section class='appendix informative'>
<h2>Acknowledgements</h2>
     
  <p>The following people have been instrumental in providing thoughts, feedback,
reviews, criticism and input in the creation of this specification:</p>

  <ul>
	<li>Martin P. Nally</li>
	<li>John Arwe</li>
	<li>Arnaud le Hors</li>
   </ul>
</section>
    
<section class='appendix informative' id="history">
<h1>Change History</h1>
<ul>
	<li>2012-09-18 - Initial ReSpec'ing of <a href="http://www.w3.org/Submission/ldbp/">Member Submission - Linked Data Basic Profile 1.0</a> (SS)</li>
	<li>2012-09-18 - Fixed up some links and worked on references, work left to do. (SS)</li>
	<li>2012-09-19 - Repairing references and forward reference to biblio.js updates (SS)</li>
	<li>2012-09-19 - Fixed rdfs:label range to be rdfs:Literal (SS)</li>
	<li>2012-09-19 - ISSUE-1 Define Turtle as the required serialization format for LDP (SS)</li>
	<li>2012-09-20 - Sent pull request re LINKED-DATA and added suggestion for <code>ldp</code> namespace (SS)</li>
	<li>2012-10-14 - Added open ISSUES and formating to prep for public working draft (SS)</li>
	<li>2012-10-15 - ISSUE-8 Changed references from LDBP to LDP, removed definition for "profile" and new namespace (SS)</li>	
	<li>2012-10-15 - Included additional open ISSUES from Oct 15 WG meeting: 22, 23, 24 (SS)</li>
	<em>First Public Working Draft</em>
	<li>2012-11-01 - Fixed minor typo and added some notes (SS)</li>
	<li>2012-11-03 - ISSUE-22, ISSUE-23: changed sections 4.2.3 and 5.4.7. Removed closed issues. (SS)</li>
	<li>2012-11-03 - ISSUE-24 Delete the phrase in 4.5.1 that nays "until ...Request URI" 
	and adding a sentence, "Clients should note that servers may reuse a Request-URI under some circumstances."</li>
	<li>2012-11-03 - ISSUE-6 Removed section 4.1.9.  Shifted up sections .10 through .13.</li>
	<li>2012-11-05 - minor rewording from ISSUE-24</li>
	<li>2012-12-28 - Fixed Typos.  Separated some compound rules like 4.1.5.  Rewording for clarity: 4.1.10, 
	Text being repeated in several places centralized and cross-linked.  Made printed code output easier to read
	on black & white printers.  Exposed terms defined in-line under LDPC as Terminology (tentatively).  Removed non-normative
	qualifer from section 5.2.  Added "several" editors' to-dos.(JA)</li>
	<li>2013-01-16 - ISSUE-25 Updated introduction. 5.2.2 changed to MUST NOT be in multiple containers. Flipped 5.6.1/2 as 
	first rule leads to 2nd. 5.6.2(was .1) Delete LDPC MUST also delete members. (SS)</li>
	<li>2013-01-16 - Added new issues ranging from 26-43. Removed closed/deferred issues: 2 & 3 (SS)</li>
</ul></section>

<section class='appendix informative' id="todos">
<h1>Editor Todos and Notes</h1>
<p>Other than LDP <a href="http://www.w3.org/2012/ldp/track/actions">open actions</a> and <a href="http://www.w3.org/2012/ldp/track/issues">issues</a>, included here are transient tasks and notes
editors use.  They have not meaning in final product of a published working draft and will be removed prior to publishing.</p>
<ul>
	<li>Insert some additional examples</li>
	<li>Expand on status code usages</li>
	<li>Editor(Steve) to consider structure based on feedback from tbl and others</li>
	<li>4.1.2: "the" subject ?= Request-URI  ... not always (hash URIs)
	</li>
	<li>4.1.4: Location or Content-Location?
	</li>
	<li>4.1.5: refers to RDF *Primer* - is that intentful?
	</li>
	<li>4.1.6.1: why does it have the extra .1, to avoid renumbering?  should we divide General into subsections
	for vocab/client/server constraints?  Do we need to define "LDPR server"? ...think about role vs artifact.  If
	"an LDPR server" hosts both LDPRs and non-LDPR HTTP resources, 4.1.2 (if "the code" == LDPR server) could be
	read to say that in order to conform to spec it must serve up RDF for non-LDPRs.  Hits 5.2.1 too.
	</li>
	<li>4.1.7: define "explicitly"?
	</li>
	<li>4.4.1: specifically calls out 2 props; issue-11 note talks about "server-managed props" which is not defined.
	</li>
	<li>4.4.4/4.4.5 could be read to overlap/dup one another
	</li>
	<li>4.8 talks about rdfs:Range which implies inferencing.  4.1.7 spec says want to avoid putting that reqt on clients.
	</li>
	<li>5.2.1: 4.1.6.1 issue linked to this text
	</li>
	<li>5.2.2: I think we mean "resource" == any HTTP resource, not just LDPR.  If so, perhaps we should be more explicit.
	5.2.1 might be the place.
	</li>
	<li>5.2.3-5.2.5: don't we need to tell clients to fetch LDPC's non-member properties, introspect for these predicates,
	and (if either not found) supply the defaults?  that is the net effect of what's here.
	</li>
	<li>5.4.5: in light of the existence of server-managed properties, why not allow response body from create?
	</li>
	<li>
	</li>
</ul>

	<div class="ldp-issue">
	<div class="ldp-issue-title"><a href="http://www.w3.org/2012/ldp/track/issues/5">ISSUE-5</a></div>
	Add a section explaining how LDP is related to Graph Store Protocol
	</div>
</section>
    
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