specification/protocol.html at d1b2cb2b294e8a6596fb6f1383df4b193696eedb · solid/specification · GitHub

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<!DOCTYPE html>
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    <meta charset="utf-8" />
    <title>Solid Protocol</title>
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    <header>
      <address>
        <a class="logo" href="https://solidproject.org/"><img alt="Solid Project" height="66" src="https://solidproject.org/TR/solid.svg" width="72" /></a>
      </address>
    </header>

    <main>
      <article about="" typeof="schema:Article doap:Specification">
        <h1 property="schema:name">Solid Protocol</h1>

        <p id="w3c-state">Version <span property="doap:revision">0.10.0</span>, <time>2022-12-31</time></p>

        <details open="">
          <summary>More details about this document</summary>

          <dl id="document-identifier">
            <dt>This version</dt>
            <dd><a href="https://solidproject.org/TR/2022/protocol-20221231" rel="owl:sameAs mem:memento">https://solidproject.org/TR/2022/protocol-20221231</a></dd>
          </dl>

          <dl id="document-latest-published-version">
            <dt>Latest published version</dt>
            <dd><a href="https://solidproject.org/TR/protocol" rel="rel:latest-version">https://solidproject.org/TR/protocol</a></dd>
          </dl>

          <dl id="document-previous-version">
            <dt>Previous version</dt>
            <dd><a href="https://solidproject.org/TR/2021/protocol-20211217" rel="rel:predecessor-version">https://solidproject.org/TR/2021/protocol-20211217</a></dd>
          </dl>

          <dl id="document-editors-draft">
            <dt>Editor’s draft</dt>
            <dd><a href="https://solidproject.org/ED/protocol" rel="rdfs:seeAlso">https://solidproject.org/ED/protocol</a></dd>
          </dl>

          <dl id="document-timemap">
            <dt>TimeMap</dt>
            <dd><a href="https://solidproject.org/TR/protocol.timemap" rel="mem:timemap">https://solidproject.org/TR/protocol.timemap</a></dd>
          </dl>

          <dl id="document-editors">
            <dt>Editors</dt>
            <dd id="Sarven-Capadisli"><span about="" rel="schema:creator schema:editor schema:author"><span about="https://csarven.ca/#i" typeof="schema:Person"><a href="https://csarven.ca/" rel="schema:url"><span about="https://csarven.ca/#i" property="schema:name"><span property="schema:givenName">Sarven</span> <span property="schema:familyName">Capadisli</span></span></a></span></span></dd>

            <dd id="Tim-Berners-Lee"><span about="" rel="schema:editor schema:author"><span about="https://www.w3.org/People/Berners-Lee/card#i" typeof="schema:Person"><a href="https://www.w3.org/People/Berners-Lee/" rel="schema:url"><span about="https://www.w3.org/People/Berners-Lee/card#i" property="schema:name"><span property="schema:givenName">Tim</span> <span property="schema:familyName">Berners-Lee</span></span></a></span></span></dd>

            <dd id="Ruben-Verborgh"><span about="" rel="schema:editor schema:author"><span about="https://ruben.verborgh.org/profile/#me" typeof="schema:Person"><a href="https://ruben.verborgh.org/" rel="schema:url"><span about="https://ruben.verborgh.org/profile/#me" property="schema:name"><span property="schema:givenName">Ruben</span> <span property="schema:familyName">Verborgh</span></span></a></span></span></dd>

            <dd id="Kjetil-Kjernsmo"><span about="" rel="schema:editor schema:author"><span about="http://www.kjetil.kjernsmo.net/foaf#me" typeof="schema:Person"><a href="http://kjetil.kjernsmo.net/" rel="schema:url"><span about="http://www.kjetil.kjernsmo.net/foaf#me" property="schema:name"><span property="schema:givenName">Kjetil</span> <span property="schema:familyName">Kjernsmo</span></span></a></span></span></dd>
          </dl>

          <dl id="document-published">
            <dt>Published</dt>
            <dd><time content="2020-12-16T00:00:00Z" datatype="xsd:dateTime" datetime="2020-12-16T00:00:00Z" property="schema:datePublished">2020-12-16</time></dd>
          </dl>

          <dl id="document-modified">
            <dt>Modified</dt>
            <dd><time content="2022-12-31T00:00:00Z" datatype="xsd:dateTime" datetime="2022-12-31T00:00:00Z" property="schema:dateModified">2022-12-31</time></dd>
          </dl>

          <dl id="document-repository">
            <dt>Repository</dt>
            <dd><a href="https://github.com/solid/specification" rel="doap:repository">GitHub</a></dd>
            <dd><a href="https://github.com/solid/specification/issues" rel="doap:bug-database">Issues</a></dd>
          </dl>

         <dl id="document-language">
            <dt>Language</dt>
            <dd><span content="en" lang="" property="dcterms:language" xml:lang="">English</span></dd>
          </dl>

          <dl id="document-license">
            <dt>License</dt>
            <dd><a href="http://purl.org/NET/rdflicense/MIT1.0" rel="schema:license">MIT License</a></dd>
          </dl>

          <dl id="document-status">
            <dt>Document Status</dt>
            <dd prefix="pso: http://purl.org/spar/pso/" rel="pso:holdsStatusInTime" resource="#b8028e44-185c-4b71-9c9f-d6e6b7c751d8"><span rel="pso:withStatus" resource="http://purl.org/spar/pso/published" typeof="pso:PublicationStatus">Published</span></dd>
          </dl>

          <dl id="document-in-reply-to">
            <dt>In Reply To</dt>
            <dd><a href="https://solidproject.org/origin" rel="as:inReplyTo">Solid Origin</a></dd>
          </dl>

          <dl id="document-policy">
            <dt>Policy</dt>
            <dd>
              <dl id="document-policy-offer" rel="odrl:hasPolicy" resource="#document-policy-offer" typeof="odrl:Policy">
                <dt>Rule</dt>
                <dd><a about="#document-policy-offer" href="https://www.w3.org/TR/odrl-vocab/#term-Offer" typeof="odrl:Offer">Offer</a></dd>
                <dt>Unique Identifier</dt>
                <dd><a href="https://solidproject.org/TR/protocol#document-policy-offer" rel="odrl:uid">https://solidproject.org/TR/protocol#document-policy-offer</a></dd>
                <dt>Target</dt>
                <dd><a href="https://solidproject.org/TR/protocol" rel="odrl:target">https://solidproject.org/TR/protocol</a></dd>
                <dt>Permission</dt>
                <dd>
                  <dl id="document-permission" rel="odrl:permission" resource="#document-permission" typeof="odrl:Permission">
                    <dt>Assigner</dt>
                    <dd><a href="https://www.w3.org/groups/cg/solid" rel="odrl:assigner">W3C Solid Community Group</a></dd>
                    <dt>Action</dt>
                    <dd>
                      <ul rel="odrl:action">
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-aggregate" resource="odrl:aggregate">Aggregate</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-archive" resource="odrl:archive">Archive</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-concurrentUse" resource="odrl:concurrentUse">Concurrent Use</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-DerivativeWorks" resource="http://creativecommons.org/ns#DerivativeWorks">Derivative Works</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-derive" resource="odrl:derive">Derive</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-digitize" resource="odrl:digitize">Digitize</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-display" resource="odrl:display">Display</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-Distribution" resource="http://creativecommons.org/ns#Distribution">Distribution</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-index" resource="odrl:index">Index</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-inform" resource="odrl:inform">Inform</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-install" resource="odrl:install">Install</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-Notice" resource="http://creativecommons.org/ns#Notice">Notice</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-present" resource="odrl:present">Present</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-print" resource="odrl:print">Print</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-read" resource="odrl:read">Read</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-reproduce" resource="odrl:reproduce">Reproduce</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-Reproduction" resource="http://creativecommons.org/ns#Reproduction">Reproduction</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-stream" resource="odrl:stream">Stream</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-synchronize" resource="odrl:synchronize">Synchronize</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-textToSpeech" resource="odrl:textToSpeech">Text-to-speech</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-transform" resource="odrl:transform">Transform</a></li>
                        <li><a href="https://www.w3.org/TR/odrl-vocab/#term-translate" resource="odrl:translate">Translate</a></li>
                      </ul>
                    </dd>
                  </dl>
                </dd>
              </dl>
            </dd>
          </dl>
        </details>

        <p class="copyright">MIT License. Copyright © 2019–2022 <a href="https://www.w3.org/groups/cg/solid">W3C Solid Community Group</a>.</p>

        <div datatype="rdf:HTML" id="content" property="schema:description">
          <section id="abstract">
            <h2>Abstract</h2>
            <div datatype="rdf:HTML" property="schema:abstract">
              <p>This document connects a set of specifications that, together, provide applications with secure and permissioned access to externally stored data in an interoperable way.</p>
            </div>
          </section>

          <section id="sotd" inlist="" rel="schema:hasPart" resource="#sotd">
            <h2 property="schema:name">Status of This Document</h2>
            <div datatype="rdf:HTML" property="schema:description">
              <p>This section describes the status of this document at the time of its publication.</p>

              <p>This document was published by the <a href="https://www.w3.org/groups/cg/solid">Solid Community Group</a> as <em>Version 0.10.0</em>. The sections that have been incorporated have been reviewed following the <a href="https://github.com/solid/process">Solid process</a>. However, the information in this document is still subject to change. You are invited to <a href="https://github.com/solid/specification/issues">contribute</a> any feedback, comments, or questions you might have.</p>

              <p>Publication as <em>Version 0.10.0</em> does not imply endorsement by the <abbr title="World Wide Web Consortium">W3C</abbr> Membership. This document may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.</p>

              <p>This document was produced by a group operating under the <a href="https://www.w3.org/community/about/process/cla/">W3C Community Contributor License Agreement (CLA)</a>. A human-readable <a href="https://www.w3.org/community/about/process/cla-deed/">summary</a> is available.</p>
            </div>
          </section>

          <nav id="toc">
            <h2 id="table-of-contents">Table of Contents</h2>
            <div>
              <ol class="toc">
                <li class="tocline">
                  <a class="tocxref" href="#abstract">Abstract</a>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#sotd">Status of This Document</a>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#introduction"><span class="secno">1</span> <span class="content">Introduction</span></a>
                  <ol>
                    <li><a href="#terminology"><span class="secno">1.1</span> <span class="content">Terminology</span></a></li>
                    <li><a href="#namespaces"><span class="secno">1.2</span> <span class="content">Namespaces</span></a></li>
                    <li><a href="#conformance"><span class="secno">1.3</span> <span class="content">Conformance</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#http"><span class="secno">2</span> <span class="content">Hypertext Transfer Protocol</span></a>
                  <ol>
                    <li><a href="#http-server"><span class="secno">2.1</span> <span class="content">HTTP Server</span></a></li>
                    <li><a href="#http-client"><span class="secno">2.2</span> <span class="content">HTTP Client</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#identifiers"><span class="secno">3</span> <span class="content">Resource Identifiers</span></a>
                  <ol>
                    <li><a href="#iris"><span class="secno">3.1</span> <span class="content">Internationalized Resource Identifiers</span></a></li>
                    <li><a href="#uri-slash-semantics"><span class="secno">3.2</span> <span class="content">URI Slash Semantics</span></a></li>
                    <li><a href="#uri-persistence"><span class="secno">3.3</span> <span class="content">URI Persistence</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#resources"><span class="secno">4</span> <span class="content">Resources</span></a>
                  <ol>
                    <li><a href="#storage-resource"><span class="secno">4.1</span> <span class="content">Storage Resource</span></a></li>
                    <li><a href="#resource-containment"><span class="secno">4.2</span> <span class="content">Resource Containment</span></a></li>
                    <li><a href="#auxiliary-resources"><span class="secno">4.3</span> <span class="content">Auxiliary Resources</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#reading-writing-resources"><span class="secno">5</span> <span class="content">Reading and Writing Resources</span></a>
                  <ol>
                    <li><a href="#resource-type-heuristics"><span class="secno">5.1</span> <span class="content">Resource Type Heuristics</span></a></li>
                    <li><a href="#reading-resources"><span class="secno">5.2</span> <span class="content">Reading Resources</span></a></li>
                    <li><a href="#writing-resources"><span class="secno">5.3</span> <span class="content">Writing Resources</span></a></li>
                    <li><a href="#deleting-resources"><span class="secno">5.4</span> <span class="content">Deleting Resources</span></a></li>
                    <li><a href="#resource-representations"><span class="secno">5.5</span> <span class="content">Resource Representations</span></a></li>
                    <li><a href="#constraints-problem-details"><span class="secno">5.6</span> <span class="content">Constraints and Problem Details</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#linked-data-notifications"><span class="secno">6</span> <span class="content">Linked Data Notifications</span></a>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#live-update"><span class="secno">7</span> <span class="content">Live Update</span></a>
                  <ol>
                    <li><a href="#notifications-protocol"><span class="secno">7.1</span> <span class="content">Solid Notifications Protocol</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#cors"><span class="secno">8</span> <span class="content">Cross-Origin Resource Sharing</span></a>
                  <ol>
                    <li><a href="#cors-server"><span class="secno">8.1</span> <span class="content">CORS Server</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#identity"><span class="secno">9</span> <span class="content">Identity</span></a>
                  <ol>
                    <li><a href="#webid"><span class="secno">9.1</span> <span class="content">WebID</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#authentication"><span class="secno">10</span> <span class="content">Authentication</span></a>
                  <ol>
                    <li><a href="#solid-oidc"><span class="secno">10.1</span> <span class="content">Solid-OIDC</span></a></li>
                    <li><a href="#webid-tls"><span class="secno">10.2</span> <span class="content">WebID-TLS</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#authorization"><span class="secno">11</span> <span class="content">Authorization</span></a>
                  <ol>
                    <li><a href="#web-access-control"><span class="secno">11.1</span> <span class="content">Web Access Control</span></a></li>
                    <li><a href="#access-control-policy"><span class="secno">11.2</span> <span class="content">Access Control Policy</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#http-definitions"><span class="secno">12</span> <span class="content">HTTP Definitions</span></a>
                  <ol>
                    <li><a href="#http-headers"><span class="secno">12.1</span> <span class="content">HTTP Headers</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#considerations"><span class="secno">13</span> <span class="content">Considerations</span></a>
                  <ol>
                    <li><a href="#security-considerations"><span class="secno">13.1</span> <span class="content">Security Considerations</span></a></li>
                    <li><a href="#privacy-considerations"><span class="secno">13.2</span> <span class="content">Privacy Considerations</span></a></li>
                    <li><a href="#accessibility-considerations"><span class="secno">13.3</span> <span class="content">Accessibility Considerations</span></a></li>
                    <li><a href="#internationalization-considerations"><span class="secno">13.4</span> <span class="content">Internationalization Considerations</span></a></li>
                    <li><a href="#security-privacy-review"><span class="secno">13.5</span> <span class="content">Security and Privacy Review</span></a></li>
                    <li><a href="#societal-impact-review"><span class="secno">13.6</span> <span class="content">Societal Impact Review</span></a></li>
                  </ol>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#change-log"><span class="secno"></span> <span class="content">Change Log</span></a>
                </li>
                <li class="tocline">
                  <a class="tocxref" href="#references"><span class="secno"></span> <span class="content">References</span></a>
                  <ol>
                    <li><a href="#normative-references"><span class="secno"></span> <span class="content">Normative References</span></a></li>
                    <li><a href="#informative-references"><span class="secno"></span> <span class="content">Informative References</span></a></li>
                  </ol>
                </li>
              </ol>
            </div>
          </nav>

          <section id="introduction" inlist="" rel="schema:hasPart" resource="#introduction">
            <h2 about="#introduction" property="schema:name" typeof="deo:Introduction">Introduction</h2>
            <div datatype="rdf:HTML" property="schema:description">
              <p><em>This section is non-normative.</em></p>

              <p>The aims of the Solid project are in line with those of the Web itself: empowerment towards <q cite="https://www.w3.org/TR/ethical-web-principles/">an equitable, informed and interconnected society</q>. Solid adds to existing Web standards to realise a space where individuals can maintain their autonomy, control their data and privacy, and choose applications and services to fulfil their needs.</p>

              <p>The Solid ecosystem encapsulates a set of specifications that are guided by the principles we have adopted and also the priority of our values. We acknowledge that every technical decision has ethical implications both for the end user (short-term) as well as society (long-term). To contribute towards a net positive social benefit, we use the <cite><a href="https://www.w3.org/TR/ethical-web-principles/" rel="cito:citesForInformation">Ethical Web Principles</a></cite> [<cite><a class="bibref" href="#bib-ethical-web-principles">ETHICAL-WEB-PRINCIPLES</a></cite>] to orient ourselves. The consensus on the technical designs are informed by common use cases, implementation experience, and use.</p>

              <p>An overarching design goal of the Solid ecosystem is to be evolvable and to provide fundamental affordances for decentralised Web applications for information exchange in a way that is secure and privacy respecting. In this environment, actors allocate identifiers for their content, shape and store data where they have access to, set access controls, and use preferred applications and services to achieve them.</p>

              <p>The general architectural principles of Solid specifications are borrowed from the <cite><a href="https://www.w3.org/TR/webarch/" rel="cito:citesForInformation">Architecture of the World Wide Web</a></cite> [<cite><a class="bibref" href="#bib-webarch">WEBARCH</a></cite>]. The components as described in each specification may evolve independently – according to the principle of orthogonality in order to increase the flexibility and robustness of the Solid ecosystem. With that, the specifications are loosely coupled and indicate which features overlap with those governed by another specification. Extensibility as well as variability also are taken into account in each specification.</p>

              <p>The specifications in the ecosystem describe how Solid servers and clients can be interoperable by using Web communication protocols, global identifiers, authentication and authorization mechanisms, data formats and shapes, and query interfaces.</p>

              <p>The specifications are accompanied with supplemental documents, such as <em>Primers</em> and <em>Best Practices and Guidelines</em> to help implementers to form a well-rounded understanding of the Solid ecosystem as well as ways to improve their implementations.</p>

              <p>This specification is for:</p>

              <ul>
                <li>Resource server developers that want to enable clients to send and retrieve information;</li>
                <li>Application developers that want to implement a client to perform operations on resources.</li>
              </ul>

              <section id="terminology" inlist="" rel="schema:hasPart" resource="#terminology" typeof="skos:ConceptScheme">
                <h3 property="schema:name skos:prefLabel">Terminology</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p><em>This section is non-normative.</em></p>

                  <p property="skos:definition">The Solid Protocol specification defines the following terms. These terms are referenced throughout this specification.</p>

                  <span rel="skos:hasTopConcept"><span resource="#storage"></span><span resource="#solid-app"></span><span resource="#uniform-resource-identifier"></span><span resource="#resource"></span><span resource="#container-resource"></span><span resource="#root-container"></span><span resource="#resource-metadata"></span><span resource="#agent"></span><span resource="#owner"></span><span resource="#origin"></span><span resource="#read-operation"></span><span resource="#write-operation"></span><span resource="#append-operation"></span></span>

                  <dl>
                    <dt about="#storage" property="skos:prefLabel" typeof="skos:Concept"><dfn id="storage">storage</dfn></dt>
                    <dd about="#storage" property="skos:definition">A storage is a space of URIs that affords agents controlled access to resources.</dd>

                    <dt about="#solid-app" property="skos:prefLabel" typeof="skos:Concept"><dfn id="solid-app">Solid app</dfn></dt>
                    <dd about="#solid-app" property="skos:definition">A Solid app is an application that reads or writes data from one or more <a href="#storage">storages</a>.</dd>

                    <dt about="#iri" property="skos:prefLabel" typeof="skos:Concept"><dfn id="iri">IRI</dfn></dt>
                    <dd about="#iri" property="skos:definition">An <dfn>Internationalized Resource Identifier</dfn> (<abbr title="Internationalized Resource Identifier">IRI</abbr>) is an identifier as defined in [<cite><a class="bibref" href="#bib-rfc3987">RFC3987</a></cite>], which identifies an entity in a global context, using a Unicode character sequence [<cite><a class="bibref" href="#bib-unicode">UNICODE</a></cite>].</dd>

                    <dt about="#uniform-resource-identifier" property="skos:prefLabel" typeof="skos:Concept"><dfn id="uniform-resource-identifier">URI</dfn></dt>
                    <dd about="#uniform-resource-identifier" property="skos:definition">A <dfn>Uniform Resource Identifier</dfn> (<abbr title="Uniform Resource Identifier">URI</abbr>) is an identifier as defined in [<cite><a class="bibref" href="#bib-rfc3987">RFC3986</a></cite>], which identifies an entity in a global context, using an ASCII character sequence [<cite><a class="bibref" href="#bib-ascii">ASCII</a></cite>]. Every URI is also an IRI.</dd>

                    <dt about="#resource" property="skos:prefLabel" typeof="skos:Concept"><dfn id="resource">resource</dfn></dt>
                    <dd about="#resource" property="skos:definition">A resource is the target of an HTTP request identified by a URI [<cite><a class="bibref" href="#bib-rfc7231">RFC7231</a></cite>].</dd>

                    <dt about="#container-resource" property="skos:prefLabel" typeof="skos:Concept"><dfn id="container-resource">container resource</dfn></dt>
                    <dd about="#container-resource" property="skos:definition">A container resource is a hierarchical collection of resources that contains other resources, including containers.</dd>

                    <dt about="#root-container" property="skos:prefLabel" typeof="skos:Concept"><dfn id="root-container">root container</dfn></dt>
                    <dd about="#root-container" property="skos:definition">A root container is a container resource that is at the highest level of the collection hierarchy.</dd>

                    <dt about="#resource-metadata" property="skos:prefLabel" typeof="skos:Concept"><dfn id="resource-metadata">resource metadata</dfn></dt>
                    <dd about="#resource-metadata" property="skos:definition">Resource metadata encompasses data about resources described by means of RDF statements [<cite><a class="bibref" href="#bib-rdf11-concepts">RDF11-CONCEPTS</a></cite>].</dd>

                    <dt about="#agent" property="skos:prefLabel" typeof="skos:Concept"><dfn id="agent">agent</dfn></dt>
                    <dd about="#agent" property="skos:definition">An agent is a person, social entity, or software identified by a URI; e.g., a WebID denotes an agent [<cite><a class="bibref" href="#bib-webid">WEBID</a></cite>].</dd>

                    <dt about="#owner" property="skos:prefLabel" typeof="skos:Concept"><dfn id="owner">owner</dfn></dt>
                    <dd about="#owner" property="skos:definition">An owner is a person or a social entity that is considered to have the rights and responsibilities of a storage. An owner is identified by a URI, and implicitly has control over all resources in a storage. An owner is first set at storage provisioning time and can be changed.</dd>

                    <dt about="#origin" property="skos:prefLabel" typeof="skos:Concept"><dfn id="origin">origin</dfn></dt>
                    <dd about="#origin" property="skos:definition">An origin indicates where an HTTP request originates from [<cite><a class="bibref" href="#bib-rfc6454">RFC6454</a></cite>].</dd>

                    <dt about="#read-operation" property="skos:prefLabel" typeof="skos:Concept"><dfn id="read-operation">read operation</dfn></dt>
                    <dd about="#read-operation" property="skos:definition">A read operation entails that information about a resource’s existence or its description can be known. [<a href="https://github.com/solid/specification/issues/149#issue-568433265" rel="cito:citesAsSourceDocument">Source</a>]</dd>

                    <dt about="#write-operation" property="skos:prefLabel" typeof="skos:Concept"><dfn id="write-operation">write operation</dfn></dt>
                    <dd about="#write-operation" property="skos:definition">A write operation entails that information about resources can be created or removed. [<a href="https://github.com/solid/specification/issues/126#issuecomment-569920473" rel="cito:citesAsSourceDocument">Source</a>]</dd>

                    <dt about="#append-operation" property="skos:prefLabel" typeof="skos:Concept"><dfn id="append-operation">append operation</dfn></dt>
                    <dd about="#append-operation" property="skos:definition">An append operation entails that information can be added but not removed. [<a href="https://github.com/solid/specification/issues/118#issuecomment-569648485" rel="cito:citesAsSourceDocument">Source</a>]</dd>
                  </dl>
                </div>
              </section>

              <section id="namespaces" inlist="" rel="schema:hasPart" resource="#namespaces">
                <h3 property="schema:name">Namespaces</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <table>
                    <caption>Prefixes and Namespaces</caption>
                    <thead>
                      <tr>
                        <th>Prefix</th>
                        <th>Namespace</th>
                        <th>Description</th>
                      </tr>
                    </thead>
                    <tbody>
                      <tr>
                        <td><code>rdf</code></td>
                        <td>http://www.w3.org/1999/02/22-rdf-syntax-ns#</td>
                        <td>[<cite><a class="bibref" href="#bib-rdf-schema">rdf-schema</a></cite>]</td>
                      </tr>
                      <tr>
                        <td><code>ldp</code></td>
                        <td>http://www.w3.org/ns/ldp#</td>
                        <td>[<cite><a class="bibref" href="#bib-ldp">LDP</a></cite>]</td>
                      </tr>
                      <tr>
                        <td><code>solid</code></td>
                        <td>http://www.w3.org/ns/solid/terms#</td>
                        <td>Solid Terms</td>
                      </tr>
                      <tr>
                        <td><code>pim</code></td>
                        <td>http://www.w3.org/ns/pim/space#</td>
                        <td>Workspace Ontology</td>
                      </tr>
                      <tr>
                        <td><code>acl</code></td>
                        <td>http://www.w3.org/ns/auth/acl#</td>
                        <td>ACL Ontology</td>
                      </tr>
                      <tr>
                        <td><code>dcterms</code></td>
                        <td>http://purl.org/dc/terms/</td>
                        <td>[<cite><a class="bibref" href="#bib-dc-terms">DC-TERMS</a></cite>]</td>
                      </tr>
                      <tr>
                        <td><code>stat</code></td>
                        <td>http://www.w3.org/ns/posix/stat</td>
                        <td>POSIX File Status</td>
                      </tr>
                    </tbody>
                  </table>
                </div>
              </section>

              <section id="conformance" inlist="" rel="schema:hasPart" resource="#conformance">
                <h3 property="schema:name">Conformance</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p>This section describes the <span about="" rel="spec:conformance" resource="#conformance">conformance model of the Solid Protocol</span>.</p>

                  <section id="normative-informative-content" inlist="" rel="schema:hasPart" resource="#normative-informative-content">
                    <h4 property="schema:name">Normative and Informative Content</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p id="normative-informative-sections">All assertions, diagrams, examples, and notes are non-normative, as are all sections explicitly marked non-normative. Everything else is normative.</p>

                      <p id="requirement-levels">The key words “<span rel="dcterms:subject" resource="spec:MUST">MUST</span>”, “<span rel="dcterms:subject" resource="spec:MUSTNOT">MUST NOT</span>”, “<span rel="dcterms:subject" resource="spec:SHOULD">SHOULD</span>”, and “<span rel="dcterms:subject" resource="spec:MAY">MAY</span>” are to be interpreted as described in <a href="https://www.rfc-editor.org/info/bcp14">BCP 14</a> [<cite><a class="bibref" href="#bib-rfc2119">RFC2119</a></cite>] [<cite><a class="bibref" href="#bib-rfc8174">RFC8174</a></cite>] when, and only when, they appear in all capitals, as shown here.</p>

                      <p id="advisement-levels">The key words “<span rel="dcterms:subject" resource="spec:StronglyEncouraged">strongly encouraged</span>”, “<span rel="dcterms:subject" resource="spec:StronglyDiscouraged">strongly discouraged</span>”, “<span rel="dcterms:subject" resource="spec:Encouraged">encouraged</span>", “<span rel="dcterms:subject" resource="spec:Discouraged">discouraged</span>", “<span rel="dcterms:subject" resource="spec:Can">can</span>", “<span rel="dcterms:subject" resource="spec:Cannot">cannot</span>”, “<span rel="dcterms:subject" resource="spec:Could">could</span>”, “<span rel="dcterms:subject" resource="spec:CouldNot">could not</span>”, “<span rel="dcterms:subject" resource="spec:Might">might</span>”, and “<span rel="dcterms:subject" resource="spec:MightNot">might not</span>” are used for non-normative content.</p>
                    </div>
                  </section>

                  <section id="specification-category" inlist="" rel="schema:hasPart spec:specificationCategory" resource="#specification-category" typeof="skos:ConceptScheme">
                    <h4 property="schema:name skos:prefLabel">Specification Category</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p property="skos:definition">The <span about="" rel="spec:specificationCategory" resource="#specification-category">Solid Protocol</span> identifies the following <cite><a href="https://www.w3.org/TR/spec-variability/#spec-cat" rel="dcterms:subject" resource="spec:SpecificationCategory">Specification Category</a></cite> to distinguish the types of conformance: <span rel="skos:hasTopConcept" resource="spec:API">API</span>, <span rel="skos:hasTopConcept" resource="spec:NotationSyntax">notation/syntax</span>, <span rel="skos:hasTopConcept" resource="spec:SetOfEvents">set of events</span>, <span rel="skos:hasTopConcept" resource="spec:ProcessorBehaviour">processor behaviour</span>, <span rel="skos:hasTopConcept" resource="spec:Protocol">protocol</span>.</p>
                    </div>
                  </section>

                  <section id="classes-of-products" inlist="" rel="schema:hasPart" resource="#classes-of-products" typeof="skos:ConceptScheme">
                    <h4 property="schema:name skos:prefLabel">Classes of Products</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p property="skos:definition">The <span about="" rel="spec:classesOfProducts" resource="#classes-of-products">Solid Protocol</span> identifies the following <cite><a href="https://www.w3.org/TR/qaframe-spec/#cop-def" rel="dcterms:subject" resource="spec:ClassesOfProducts">Classes of Products</a></cite> for conforming implementations. These products are referenced throughout this specification.</p>

                      <span rel="skos:hasTopConcept"><span resource="#Server"></span><span resource="#Client"></span></span>

                      <dl>
                        <dt about="#Server" property="skos:prefLabel" rel="skos:relatedMatch" resource="spec:RespondingAgent" typeof="skos:Concept"><dfn id="Server">Server</dfn></dt>
                        <dd about="#Server" property="skos:definition">A <a href="#http-server" rel="rdfs:seeAlso">server</a> that builds on HTTP <cite>server</cite> [<cite><a class="bibref" href="#bib-rfc7230">RFC7230</a></cite>] and [<cite><a class="bibref" href="#bib-rfc7231">RFC7231</a></cite>] by defining media types, HTTP header fields, and the behaviour of resources, as identified by link relations.</dd>
                        <dt about="#Client" property="skos:prefLabel" rel="skos:relatedMatch" resource="spec:Consumer" typeof="skos:Concept"><dfn id="Client">Client</dfn></dt>
                        <dd about="#Client" property="skos:definition">A <a href="#http-client" rel="rdfs:seeAlso">client</a> that builds on HTTP <cite>client</cite> [<cite><a class="bibref" href="#bib-rfc7230">RFC7230</a></cite>], [<cite><a class="bibref" href="#bib-rfc7231">RFC7231</a></cite>], and [<cite><a class="bibref" href="#bib-fetch">FETCH</a></cite>] by defining behaviour in terms of fetching across the platform.</dd>
                      </dl>
                    </div>
                  </section>

                  <section id="interoperability" inlist="" rel="schema:hasPart" resource="#interoperability">
                    <h4 property="schema:name skos:prefLabel">Interoperability</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p id="interoperability-server-client">Interoperability of implementations for <a href="#Server" rel="rdfs:seeAlso">servers</a> and <a href="#Client" rel="rdfs:seeAlso">clients</a> is tested by evaluating an implementation’s ability to request and respond to HTTP messages that conform to this specification.</p>
                    </div>
                  </section>
                </div>
              </section>
            </div>
          </section>

          <section id="http" inlist="" rel="schema:hasPart" resource="#http">
            <h2 property="schema:name">Hypertext Transfer Protocol</h2>
            <div datatype="rdf:HTML" property="schema:description">
              <p>Solid <a href="#Server" rel="dcterms:subject">servers</a> and <a href="#Client" rel="dcterms:subject">clients</a> need to exchange data securely over the Internet, and they do so using the HTTP Web standard. This section describes in detail which parts of HTTP must be implemented by clients and servers.</p>

              <section id="http-server" inlist="" rel="schema:hasPart" resource="#http-server">
                <h3 property="schema:name">HTTP Server</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p><span about="" id="server-http-11" rel="spec:requirement" resource="#server-http-11"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> conform to <cite>HTTP/1.1 Message Syntax and Routing</cite> [<cite><a class="bibref" href="#bib-rfc7230">RFC7230</a></cite>] and <cite>HTTP/1.1 Semantics and Content</cite> [<cite><a class="bibref" href="#bib-rfc7231">RFC7231</a></cite>].</span></span> <span about="" id="server-http-2" rel="spec:requirement" resource="#server-http-2"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:SHOULD">SHOULD</span> conform to <cite>HTTP/2</cite> [<cite><a class="bibref" href="#bib-rfc7540">RFC7540</a></cite>].</span></span></p>

                  <p><span about="" id="server-tls-https" rel="spec:requirement" resource="#server-tls-https"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:SHOULD">SHOULD</span> use TLS connections through the <code>https</code> URI scheme in order to secure the communication with clients.</span></span> <span about="" id="server-tls-https-redirect" rel="spec:requirement" resource="#server-tls-https-redirect"><span property="spec:statement">When both <code>http</code> and <code>https</code> URI schemes are supported, the <span rel="spec:requirementSubject" resource="#Server">server</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> redirect all <code>http</code> URIs to their <code>https</code> counterparts using a response with a <code>301</code> status code and a <code>Location</code> header.</span></span></p>

                  <p><span about="" id="server-conditional-requests" rel="spec:requirement" resource="#server-conditional-requests"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> conform to <cite>HTTP/1.1 Conditional Requests</cite> [<cite><a class="bibref" href="#bib-rfc7232">RFC7232</a></cite>].</span></span> <span about="" id="server-caching" rel="spec:requirement" resource="#server-caching"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:SHOULD">SHOULD</span> conform to <cite>HTTP/1.1 Caching</cite> [<cite><a class="bibref" href="#bib-rfc7234">RFC7234</a></cite>].</span></span> <span about="" id="server-range-requests" rel="spec:requirement" resource="#server-range-requests"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MAY">MAY</span> conform to <cite>HTTP/1.1 Range Requests</cite> [<cite><a class="bibref" href="#bib-rfc7233">RFC7233</a></cite>].</span></span></p>

                  <p><span about="" id="server-authentication" rel="spec:requirement" resource="#server-authentication"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> conform to <cite>HTTP/1.1 Authentication</cite> [<cite><a class="bibref" href="#bib-rfc7235">RFC7235</a></cite>].</span></span> <span about="" id="server-unauthenticated" rel="spec:requirement" resource="#server-unauthenticated"><span property="spec:statement">When a client does not provide valid credentials when requesting a resource that requires it (see <a href="#webid">WebID</a>), <span rel="spec:requirementSubject" resource="#Server">servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> send a response with a <code>401</code> status code (unless <code>404</code> is preferred for security reasons).</span></span></p>

                  <p><span about="" id="server-content-type" rel="spec:requirement" resource="#server-content-type"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Server</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> reject <code>PUT</code>, <code>POST</code> and <code>PATCH</code> requests without the <code>Content-Type</code> header with a status code of <code>400</code>.</span></span> [<a href="https://github.com/solid/specification/issues/70#issuecomment-547924171" rel="cito:citesAsSourceDocument">Source</a>]</p>
                </div>
              </section>

              <section id="http-client" inlist="" rel="schema:hasPart" resource="#http-client">
                <h3 property="schema:name">HTTP Client</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p><span about="" id="client-http-11" rel="spec:requirement" resource="#client-http-11"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Client">Clients</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> conform to <cite>HTTP/1.1 Message Syntax and Routing</cite> [<cite><a class="bibref" href="#bib-rfc7230">RFC7230</a></cite>] and <cite>HTTP/1.1 Semantics and Content</cite> [<cite><a class="bibref" href="#bib-rfc7231">RFC7231</a></cite>].</span></span> <span about="" id="client-http-2" rel="spec:requirement" resource="#client-http-2"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Client">Clients</span> <span rel="spec:requirementLevel" resource="spec:MAY">MAY</span> conform to <cite>HTTP/2</cite> [<cite><a class="bibref" href="#bib-rfc7540">RFC7540</a></cite>].</span></span></p>

                  <p><span about="" id="client-conditional-requests" rel="spec:requirement" resource="#client-conditional-requests"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Client">Clients</span> <span rel="spec:requirementLevel" resource="spec:MAY">MAY</span> conform to <cite>HTTP/1.1 Conditional Requests</cite> [<cite><a class="bibref" href="#bib-rfc7232">RFC7232</a></cite>].</span></span> <span about="" id="client-caching" rel="spec:requirement" resource="#client-caching"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Client">Clients</span> <span rel="spec:requirementLevel" resource="spec:MAY">MAY</span> conform to <cite>HTTP/1.1 Caching</cite> [<cite><a class="bibref" href="#bib-rfc7234">RFC7234</a></cite>].</span></span> <span about="" id="client-range-requests" rel="spec:requirement" resource="#client-range-requests"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Client">Clients</span> <span rel="spec:requirementLevel" resource="spec:MAY">MAY</span> conform to <cite>HTTP/1.1 Range Requests</cite> [<cite><a class="bibref" href="#bib-rfc7233">RFC7233</a></cite>].</span></span></p>

                  <p><span about="" id="client-authentication" rel="spec:requirement" resource="#client-authentication"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Client">Clients</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> conform to <cite>HTTP/1.1 Authentication</cite> [<cite><a class="bibref" href="#bib-rfc7235">RFC7235</a></cite>] if it needs to access resources requiring authentication (see <a href="#webid">WebID</a>).</span></span> <span about="" id="client-authentication-different-credentials" rel="spec:requirement" resource="#client-authentication-different-credentials"><span property="spec:statement">When a <span rel="spec:requirementSubject" resource="#Client">client</span> receives a response with a <code>403</code> or <code>404</code> status code, the client <span rel="spec:requirementLevel" resource="spec:MAY">MAY</span> repeat the request with different credentials.</span></span></p>

                  <p><span about="" id="client-content-type" rel="spec:requirement" resource="#client-content-type"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Client">Clients</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> use the <code>Content-Type</code> HTTP header in <code>PUT</code>, <code>POST</code> and <code>PATCH</code> requests [<cite><a class="bibref" href="#bib-rfc7231">RFC7231</a></cite>].</span></span> [<a href="https://github.com/solid/specification/issues/70#issuecomment-547924171" rel="cito:citesAsSourceDocument">Source</a>]</p>
                </div>
              </section>
            </div>
          </section>

          <section id="identifiers" inlist="" rel="schema:hasPart" resource="#identifiers">
            <h2 property="schema:name">Resource Identifiers</h2>
            <div datatype="rdf:HTML" property="schema:description">
              <div class="note" id="storage-owner-uri-ownership" inlist="" rel="schema:hasPart" resource="#storage-owner-uri-ownership">
                <h3 property="schema:name"><span>Note</span>: Storage Owner and URI Ownership</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p>This specification does not describe the relationship between a storage <q>owner</q> and Web architecture’s <cite><a href="https://www.w3.org/TR/webarch/#uri-ownership">URI ownership</a></cite> [<cite><a class="bibref" href="#bib-webarch">WEBARCH</a></cite>].</p>
                </div>
              </div>

              <section id="iris" inlist="" rel="schema:hasPart" resource="#iris">
                <h3 property="schema:name">Internationalized Resource Identifiers</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p id="iris-resources">All <a href="#resources">resources</a> provided by a Solid <a href="#Server">server</a> are identified by an <a href="#iri">IRI</a> with the <code>http</code> or <code>https</code> scheme, in the following normal form:</p>

                  <ul id="iris-norm">
                    <li id="iris-nfc">The IRI is a Unicode string in Normalization Form C (NFC) [<cite><a class="bibref" href="#bib-uax15">UAX15</a></cite>].</li>

                    <li id="#iris-unreserved">The IRI does not contain percent-encoding triplets corresponding to <em>unreserved</em> characters.</li>

                    <li id="iris-hex">Hexadecimal digits within percent-encoding triplets corresponding to <em>reserved</em> characters are represented using <em>uppercase</em> letters.</li>

                    <li id="iris-scheme">The <code>http</code> or <code>https</code> scheme of the IRI is represented using <em>lowercase</em> characters.</li>

                    <li id="#iris-host">The host of the IRI is represented using <em>lowercase</em> characters.</li>

                    <li id="iris-port">If the port of the IRI is the default port for its scheme, the port subcomponent is left out.</li>

                    <li id="iris-path">The path of the IRI does not contain dot-segments.</li>
                  </ul>

                  <p><span about="" id="server-iris-norm" rel="spec:requirement" resource="#server-iris-norm"><span property="spec:statement">A Solid <span rel="spec:requirementSubject" resource="#Server">server</span> <span rel="spec:requirementLevel" resource="spec:MUSTNOT">MUST NOT</span> create IRIs that do not conform to this normal form.</span></span></p>

                  <p><span about="" id="server-iris-to-http" rel="spec:requirement" resource="#server-iris-to-http"><span property="spec:statement">When using an IRI in an <a href=#http>HTTP</a> message, except in the content, a Solid <span rel="spec:requirementSubject" resource="#Server">server</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> map the IRI to a URI according to the algorithm provided by [<cite><a class="bibref" href="#bib-rfc3987">RFC3987</a></cite>] (<a href="https://datatracker.ietf.org/doc/html/rfc3987#section-3.1">section 3.1</a>).</span></span></p>

                  <p><span about="" id="server-iris-from-http" rel="spec:requirement" resource="#server-iris-from-http"><span property="spec:statement">When interpreting a URI in an <a href=#http>HTTP</a> message, except in the content, as a resource identifier, a Solid <span rel="spec:requirementSubject" resource="#Server">server</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> map the URI to an IRI according to the algorithm provided by [<cite><a class="bibref" href="#bib-rfc3987">RFC3987</a></cite>] (<a href="https://datatracker.ietf.org/doc/html/rfc3987#section-3.2">section 3.2</a>), and normalize the resulting IRI to the <a href="#iris-norm">normal form</a> provided in this section.</span></span></p>
                </div>
              </section>

              <section id="uri-slash-semantics" inlist="" rel="schema:hasPart" resource="#uri-slash-semantics">
                <h3 property="schema:name">URI Slash Semantics</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p id="uri-slashes-hierarchical-identifier">The slash (<code>/</code>) character in the URI path indicates hierarchical relationship segments, and enables relative referencing [<cite><a class="bibref" href="#bib-rfc3986">RFC3986</a></cite>]. The semantics of the slash character is shared by servers and clients. Paths ending with a slash denote a container resource. [<a href="https://github.com/solid/specification/issues/35#issuecomment-547949014" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <p><span about="" id="server-uri-trailing-slash-distinct" rel="spec:requirement" resource="#server-uri-trailing-slash-distinct"><span property="spec:statement">If two URIs differ only in the trailing slash, and the <span rel="spec:requirementSubject" resource="#Server">server</span> has associated a resource with one of them, then the other URI <span rel="spec:requirementLevel" resource="spec:MUSTNOT">MUST NOT</span> correspond to another resource.</span></span> <span about="" id="server-uri-redirect-differing" rel="spec:requirement" resource="#server-uri-redirect-differing"><span property="spec:statement">Instead, the <span rel="spec:requirementSubject" resource="#Server">server</span> <span rel="spec:requirementLevel" resource="spec:MAY">MAY</span> respond to requests for the latter URI with a 301 redirect to the former.</span></span> [<a href="https://github.com/solid/specification/issues/107#issuecomment-567482817" rel="cito:citesAsSourceDocument">Source</a>]. <span about="" id="server-authorization-redirect" rel="spec:requirement" resource="#server-authorization-redirect"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> authorize prior to this optional redirect.</span></span> [<a href="https://github.com/solid/specification/issues/107#issuecomment-567454889" rel="cito:citesAsSourceDocument">Source</a>].</p>
                </div>
              </section>

              <section id="uri-persistence" inlist="" rel="schema:hasPart" resource="#uri-persistence">
                <h3 property="schema:name">URI Persistence</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p><em>This section is non-normative.</em></p>

                  <p>Servers should not re-use URIs, regardless of the mechanism by which resources are created. Certain specific cases exist where URIs may be reinstated when it identifies the same resource, but only when consistent with Web architecture’s <cite><a href="https://www.w3.org/TR/webarch/#URI-persistence">URI persistence</a></cite> [<cite><a class="bibref" href="#bib-webarch">WEBARCH</a></cite>]. [<a href="https://github.com/solid/specification/issues/46#issuecomment-589619372" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <div class="note" id="uri-reuse" inlist="" rel="schema:hasPart" resource="#uri-reuse">
                    <h4 property="schema:name"><span>Note</span>: URI Reuse</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p>Servers that wish to disable URI re-use may want to use the <code>410</code> status code.</p>
                    </div>
                  </div>
                </div>
              </section>
            </div>
          </section>

          <section id="resources" inlist="" rel="schema:hasPart" resource="#resources">
            <h2 property="schema:name">Resources</h2>
            <div datatype="rdf:HTML" property="schema:description">
              <section id="storage-resource" inlist="" rel="schema:hasPart" resource="#storage-resource">
                <h3 property="schema:name">Storage Resource</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p><span about="" id="server-storage" rel="spec:requirement" resource="#server-storage"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> provide one or more <a href="#storage">storages</a>. The storage resource (<code>pim:Storage</code>) is the root container for all of its contained resources (see <a href="#resource-containment">Resource Containment</a>).</span></span></p>

                  <p><span about="" id="server-storage-nonoverlapping" rel="spec:requirement" resource="#server-storage-nonoverlapping"><span property="spec:statement">When a <span rel="spec:requirementSubject" resource="#Server">server</span> supports multiple storages, the URIs <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> be allocated to non-overlapping space.</span></span></p>

                  <p><span about="" id="server-link-storage" rel="spec:requirement" resource="#server-link-storage"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> advertise the storage resource by including the HTTP <code>Link</code> header with <code>rel="type"</code> targeting <code>http://www.w3.org/ns/pim/space#Storage</code> when responding to storage’s request URI.</span></span></p>

                  <p><span about="" id="client-link-storage" rel="spec:requirement" resource="#client-link-storage">Clients can determine a resource is of type storage by making an HTTP <code>HEAD</code> or <code>GET</code> request on the target URL, and checking for the <code>Link</code> header with <code>rel="type"</code> targeting <code>http://www.w3.org/ns/pim/space#Storage</code>.</span></p>

                  <p><span about="" id="client-storage-disovery" rel="spec:requirement" resource="#client-storage-discovery">Clients can determine the storage of a resource by moving up the URI path hierarchy until the response includes a <code>Link</code> header with <code>rel="type"</code> targeting <code>http://www.w3.org/ns/pim/space#Storage</code>.</span></p>

                  <p><span about="" id="client-rdf-storage" rel="spec:requirement" resource="#client-rdf-storage">Clients can discover a storage by making an HTTP <code>GET</code> request on the target URL to retrieve an RDF representation [<cite><a class="bibref" href="#bib-rdf11-concepts">RDF11-CONCEPTS</a></cite>], whose encoded RDF graph contains a relation of type <code>http://www.w3.org/ns/pim/space#storage</code>. The object of the relation is the storage (<code>pim:Storage</code>).</span></p>

                  <p>[<a href="https://github.com/solid/data-interoperability-panel/issues/10#issuecomment-598694029" rel="cito:citesAsSourceDocument">Source</a>] [<a href="https://github.com/solid/specification/issues/153#issuecomment-624630022" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <p><span about="" id="server-storage-description" rel="spec:requirement" resource="#server-storage-description"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> include the <code>Link</code> header with <code>rel="http://www.w3.org/ns/solid/terms#storageDescription"</code> targeting the URI of the storage description resource in the response of HTTP <code>GET</code>, <code>HEAD</code> and <code>OPTIONS</code> requests targeting a resource in a storage.</span></span></p>

                  <p><span about="" id="server-storage-description-resource" rel="spec:requirement" resource="#server-storage-description-resource"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> include <a href="#storage-description-statements" rel="rdfs:seeAlso">statements about the storage</a> as part of the storage description resource.</span></span></p>

                  <p about="#storage-description-statements" id="storage-description-statements" typeof="skos:Collection"><span property="skos:prefLabel">Storage description statements</span> include the properties:</p>

                  <dl about="#storage-description-statements" rel="skos:member">
                    <dt about="#storage-description-rdf-type" id="storage-description-rdf-type" property="skos:prefLabel" typeof="skos:Concept"><code>rdf:type</code></dt>
                    <dd about="#storage-description-rdf-type" property="skos:definition">A class whose URI is <code>http://www.w3.org/ns/pim/space#Storage</code>.</dd>
                  </dl>

                  <p>[<a href="https://github.com/solid/specification/issues/355" rel="cito:citesAsSourceDocument">Source</a>].</p>

                  <p><span about="" id="server-storage-track-owner" rel="spec:requirement" resource="#server-storage-track-owner"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> keep track of at least one <a href="#owner">owner</a> of a storage in an implementation defined way.</span></span></p>

                  <p><span about="" id="server-storage-link-owner" rel="spec:requirement" resource="#server-storage-link-owner"><span property="spec:statement">When a <span rel="spec:requirementSubject" resource="#Server">server</span> wants to advertise the owner of a storage, the server <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> include the <code>Link</code> header with <code>rel="http://www.w3.org/ns/solid/terms#owner"</code> targeting the URI of the owner in the response of HTTP <code>HEAD</code> or <code>GET</code> requests targeting the root container.</span></span></p>

                  <p>[<a href="https://github.com/solid/specification/issues/67" rel="cito:citesAsSourceDocument">Source</a>][<a href=" https://github.com/solid/specification/issues/132" rel="cito:citesAsSourceDocument">Source</a>][<a href="https://github.com/solid/specification/issues/153" rel="cito:citesAsSourceDocument">Source</a>][<a href="https://github.com/solid/specification/issues/197" rel="cito:citesAsSourceDocument">Source</a>]</p>
                </div>
              </section>

              <section id="resource-containment" inlist="" rel="schema:hasPart" resource="#resource-containment">
                <h3 property="schema:name">Resource Containment</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p>Solid has the notion of containers to represent a collection of linked resources to help with resource discovery and lifecycle management.</p>

                  <p id="server-hierarchical-containment">There is a 1-1 correspondence between containment triples and relative reference within the path name hierarchy. [<a href="https://github.com/solid/specification/issues/98#issuecomment-547506617" rel="cito:citesAsSourceDocument">Source</a>]. It follows that all resources are discoverable from a container and that it is not possible to create orphan resources. [<a href="https://github.com/solid/specification/issues/97#issuecomment-547459396" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <p><span about="" id="server-basic-container" rel="spec:requirement" resource="#server-basic-container"><span property="spec:statement">The representation and behaviour of containers in Solid corresponds to LDP Basic Container and <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> be supported by <span rel="spec:requirementSubject" resource="#Server">server</span>.</span></span> [<a href="https://github.com/solid/specification/issues/47#issuecomment-561675764" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <p id="server-container-last-modified">Servers can determine the value of the HTTP <code>Last-Modified</code> header field in response to <code>HEAD</code> and <code>GET</code> requests targeting a container based on changes to containment triples.</p>

                  <div class="note" id="container-last-modified-comparison" inlist="container-last-modified-comparison" rel="schema:hasPart" resource="#container-last-modified-comparison">
                    <h4 property="schema:name"><span>Note</span>: Container Last-Modified Comparison</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p>The <code>Last-Modified</code> of a container will not change when other parts of the container changes. This is to avoid instant propagation of changes all the way to the root container. As <code>Last-Modified</code> cannot be reliably used to check whether the container representation has changed in any way. In future versions of this specification, this design may be revisited.</p>
                    </div>
                  </div>

                  <section id="contained-resource-metadata" inlist="" rel="schema:hasPart" resource="#contained-resource-metadata">
                    <h4 property="schema:name">Contained Resource Metadata</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p>Container descriptions are not limited to containment triples. To further support client navigation and application interaction, servers can include <a href="#resource-metadata">resource metadata</a> about contained resources as part of the container description, as described below.</p>

                      <p><span about="" id="server-contained-resource-metadata" rel="spec:requirement" resource="#server-contained-resource-metadata"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:SHOULD">SHOULD</span> include <a href="#contained-resource-metadata-statements" rel="rdfs:seeAlso">resource metadata about contained resources</a> as part of the container description, unless that information is inapplicable to the server.</span></span></p>

                      <p about="#contained-resource-metadata-statements" id="contained-resource-metadata-statements" typeof="skos:Collection"><span property="skos:prefLabel">Contained resource metadata statements</span> include the properties:</p>

                      <dl about="#contained-resource-metadata-statements" rel="skos:member">
                        <dt about="#contained-resource-metadata-rdf-type" id="contained-resource-metadata-rdf-type" property="skos:prefLabel" typeof="skos:Concept"><code>rdf:type</code></dt>
                        <dd about="#contained-resource-metadata-rdf-type" property="skos:definition">A class whose URI is the expansion of the <em>URI Template</em> [<cite><a class="bibref" href="#bib-rfc6570">RFC6570</a></cite>] <code>http://www.w3.org/ns/iana/media-types/{+iana-media-type}#Resource</code>, where <code>iana-media-type</code> corresponds to a value from the IANA Media Types [<cite><a class="bibref" href="#bib-iana-media-types">IANA-MEDIA-TYPES</a></cite>].</dd>
                        <dt about="#contained-resource-metadata-stat-size" id="contained-resource-metadata-stat-size" property="skos:prefLabel" typeof="skos:Concept"><code>stat:size</code></dt>
                        <dd about="#contained-resource-metadata-stat-size" property="skos:definition">A non-negative integer giving the size of the resource in bytes.</dd>
                        <dt about="#contained-resource-metadata-dcterms-modified" id="contained-resource-metadata-dcterms-modified" property="skos:prefLabel" typeof="skos:Concept"><code>dcterms:modified</code></dt>
                        <dd about="#contained-resource-metadata-dcterms-modified" property="skos:definition">The date and time when the resource was last modified.</dd>
                        <dt about="#contained-resource-metadata-stat-mtime" id="contained-resource-metadata-stat-mtime" property="skos:prefLabel" typeof="skos:Concept"><code>stat:mtime</code></dt>
                        <dd about="#contained-resource-metadata-stat-mtime" property="skos:definition">The Unix time when the resource was last modified.</dd>
                      </dl>

                      <p id="dcterms-modified-corresponds-last-modified">The <code>dcterms:modified</code> value of a contained resource corresponds with the <code>Last-Modified</code> header value of the contained resource. If one were to perform <code>HEAD</code> or <code>GET</code> requests on the URI of the contained resource at the time of the HTTP message’s generation, then a response with the <code>200</code> status code including the <code>Last-Modified</code> header would indicate the same date and time.</p>

                      <div class="note" id="contained-resource-metadata-considerations" inlist="" rel="schema:hasPart" resource="#contained-resource-metadata-considerations">
                        <h5 property="schema:name"><span>Note</span>: Contained Resource Metadata Considerations</h5>
                        <div datatype="rdf:HTML" property="schema:description">
                          <p>The generation of contained resource metadata may be inapplicable to some servers, for example, when that information does not exist or is expensive to determine.</p>
                        </div>
                      </div>

                      <p>Contained resource metadata is <a href="#server-protect-contained-resource-metadata" rel="cito:discusses">protected by the server</a>.</p>

                      <p>[<a href="https://github.com/solid/specification/issues/227" rel="cito:citesAsSourceDocument">Source</a>]
                      [<a href="https://github.com/solid/specification/issues/343" rel="cito:citesAsSourceDocument">Source</a>] [<a href="https://github.com/solid/specification/pull/352" rel="cito:citesAsSourceDocument">Source</a>]</p>
                    </div>
                  </section>
                </div>
              </section>

              <section id="auxiliary-resources" inlist="" rel="schema:hasPart" resource="#auxiliary-resources">
                <h3 property="schema:name">Auxiliary Resources</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p>Solid has the notion of <em>auxiliary resources</em> to provide supplementary information such as descriptive metadata, authorization conditions, data shape constraints, digital rights or provenance record about a given resource (hereafter referred as the <em>subject resource</em>), and affects how resources and others associated with it are processed, served or interpreted.</p>

                  <p><span about="" id="server-auxiliary-resources-management" rel="spec:requirement" resource="#server-auxiliary-resources-management"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> support auxiliary resources defined by this specification and manage the association between a subject resource and auxiliary resources.</span></span> When a subject resource is deleted its auxiliary resources are also deleted by the server (<a href="#server-delete-remove-auxiliary-resource">Server Deleting Auxiliary Resources</a>).</p>

                  <p id="auxiliary-resources-rdf-document">Auxiliary resources are represented as <em>RDF document</em>s [<cite><a class="bibref" href="#bib-rdf11-concepts">RDF11-CONCEPTS</a></cite>]. HTTP interactions on auxiliary resources are subject to the requirements as per <cite><a href="#reading-writing-resources">Reading and Writing Resources</a></cite>.</p>

                  <div class="note" id="self-describing-resources" inlist="" rel="schema:hasPart" resource="#self-describing-resources">
                    <h4 property="schema:name"><span>Note</span>: Self-describing Resources</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p>Where applicable, to promote <a href="https://www.w3.org/2001/tag/doc/selfDescribingDocuments">self-describing resources</a>, implementations and authors are encouraged to use the subject resource instead of the associated auxiliary resource.</p>
                    </div>
                  </div>

                  <div class="note" id="uri-origin" inlist="" rel="schema:hasPart" resource="#uri-origin">
                    <h4 property="schema:name"><span>Note</span>: URI Origin</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p>The resource and the associated auxiliary resource can be on different origins [<cite><a class="bibref" href="#bib-rfc6454">RFC6454</a></cite>].</p>
                    </div>
                  </div>

                  <p>This specification defines the following types of auxiliary resources:</p>

                  <ul>
                    <li><a href="#auxiliary-resources-web-access-control">Web Access Control</a></li>
                    <li><a href="#auxiliary-resources-description-resource">Description Resource</a></li>
                  </ul>

                  <p><span about="" id="server-link-auxiliary-type" rel="spec:requirement" resource="#server-link-auxiliary-type"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> advertise auxiliary resources associated with a subject resource by responding to <code>HEAD</code> and <code>GET</code> requests by including the HTTP <code>Link</code> header with the <code>rel</code> parameter [<cite><a class="bibref" href="#bib-rfc8288">RFC8288</a></cite>].</span></span></p>

                  <p><span about="" id="client-link-auxiliary-type" rel="spec:requirement" resource="#client-link-auxiliary-type">Clients can discover auxiliary resources associated with a subject resource by making an HTTP <code>HEAD</code> or <code>GET</code> request on the target URL, and checking the HTTP <code>Link</code> header with the <code>rel</code> parameter [<cite><a class="bibref" href="#bib-rfc8288">RFC8288</a></cite>].</span></p>

                  <table>
                    <thead>
                      <tr>
                        <th>Auxiliary Type</th>
                        <th>Link Relation</th>
                        <th>Definitions</th>
                      </tr>
                    </thead>
                    <tbody>
                      <tr>
                        <td><a href="#auxiliary-resources-web-access-control">Web Access Control</a></td>
                        <td><code>acl</code></td>
                        <td>[<cite><a class="bibref" href="#bib-wac">WAC</a></cite>]</td>
                      </tr>
                      <tr>
                        <td><a href="#auxiliary-resources-description-resource">Description Resource</a></td>
                        <td><code>describedby</code></td>
                        <td>[<cite><a class="bibref" href="#bib-powder-dr">POWDER-DR</a></cite>]</td>
                      </tr>
                    </tbody>
                  </table>

                  <section id="auxiliary-resources-web-access-control" inlist="" rel="schema:hasPart" resource="#auxiliary-resources-web-access-control">
                    <h4 property="schema:name">Web Access Control</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p>An auxiliary resource of type <em>Web Access Control</em> provides access control description of a subject resource (<a href="#web-access-control">Web Access Control</a>).</p>
                    </div>
                  </section>

                  <section id="auxiliary-resources-description-resource" inlist="" rel="schema:hasPart" resource="#auxiliary-resources-description-resource">
                    <h4 property="schema:name">Description Resource</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p>An auxiliary resource of type <em>Description Resource</em> provides a description of a subject resource.</p>

                      <p><span about="" id="server-description-resource-max" rel="spec:requirement" resource="#server-description-resource-max"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUSTNOT">MUST NOT</span> directly associate more than one description resource to a subject resource.</span></span></p>

                      <p><span about="" id="server-description-resource-authorization" rel="spec:requirement" resource="#server-description-resource-authorization"><span property="spec:statement">When an HTTP request targets a description resource, the <span rel="spec:requirementSubject" resource="#Server">server</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> apply the authorization rule that is used for the subject resource with which the description resource is associated.</span></span></p>

                      <p><span about="" id="client-link-describes" rel="spec:requirement" resource="#client-link-describes">Clients can discover resources that are described by description resources by making an HTTP <code>HEAD</code> or <code>GET</code> request on the target URL, and checking the HTTP <code>Link</code> header with a <code>rel</code> value of <code>describes</code> (inverse of the <code>describedby</code> relation) [<cite><a class="bibref" href="#bib-rfc6892">RFC6892</a></cite>].</span></p>
                    </div>
                  </section>
                </div>
              </section>
            </div>
          </section>

          <section id="reading-writing-resources" inlist="" rel="schema:hasPart" resource="#reading-writing-resources">
            <h2 property="schema:name">Reading and Writing Resources</h2>
            <div datatype="rdf:HTML" property="schema:description">
              <p><span about="" id="server-method-not-allowed" rel="spec:requirement" resource="#server-method-not-allowed"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> respond with the <code>405</code> status code to requests using HTTP methods that are not supported by the target resource.</span></span> [<a href="https://github.com/solid/specification/issues/117" rel="cito:citesAsSourceDocument">Source</a>]</p>

              <section id="resource-type-heuristics" inlist="" rel="schema:hasPart" resource="#resource-type-heuristics">
                <h3 property="schema:name">Resource Type Heuristics</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p>When creating new resources, servers can determine an effective request URI’s type by examining the URI path ending (<a href="#uri-slash-semantics">URI Slash Semantics</a>).</p>

                  <p><span about="" id="server-put-patch-uri-assignment" rel="spec:requirement" resource="#server-put-patch-uri-assignment"><span property="spec:statement">When a successful <code>PUT</code> or <code>PATCH</code> request creates a resource, the <span rel="spec:requirementSubject" resource="#Server">server</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> use the effective request URI to assign the URI to that resource.</span></span></p>

                  <p><span about="" id="server-post-uri-assignment" rel="spec:requirement" resource="#server-post-uri-assignment"><span property="spec:statement">When a successful <code>POST</code> request creates a resource, the <span rel="spec:requirementSubject" resource="#Server">server</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> assign a URI to that resource.</span></span> <span about="" id="server-slug-uri-assignment" rel="spec:requirement" resource="#server-slug-uri-assignment"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MAY">MAY</span> allow clients to suggest the URI of a resource created through <code>POST</code>, using the HTTP <code>Slug</code> header as defined in [<cite><a class="bibref" href="#bib-rfc5023">RFC5023</a></cite>].</span></span></p>

                  <div class="note" id="uri-allocation" inlist="" rel="schema:hasPart" resource="#uri-allocation">
                    <h4 property="schema:name"><span>Note</span>: URI Allocation</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p>Clients can use <code>PUT</code> and <code>PATCH</code> requests to assign a URI to a resource. Clients can use <code>POST</code> requests to have the server assign a URI to a resource.</p>
                    </div>
                  </div>

                  <p>[<a href="https://github.com/solid/specification/pull/160#issuecomment-636822687" rel="cito:citesAsSourceDocument">Source</a>][<a href="https://github.com/solid/specification/pull/263" rel="cito:citesAsSourceDocument">Source</a>].</p>
                </div>
              </section>

              <section id="reading-resources" inlist="" rel="schema:hasPart" resource="#reading-resources">
                <h3 property="schema:name">Reading Resources</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p><span about="" id="server-safe-methods" rel="spec:requirement" resource="#server-safe-methods"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> support the HTTP <code>GET</code>, <code>HEAD</code> and <code>OPTIONS</code> methods [<cite><a class="bibref" href="#bib-rfc7231">RFC7231</a></cite>] for clients to read resources or to determine communication options.</span></span> [<a href="https://github.com/solid/specification/issues/39#issuecomment-538017667" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <p><span about="" id="server-allow-methods" rel="spec:requirement" resource="#server-allow-methods"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> indicate the HTTP methods supported by the target resource by generating an <code>Allow</code> header field in successful responses.</span></span></p>

                  <p><span about="" id="server-accept-headers" rel="spec:requirement" resource="#server-accept-headers"><span property="spec:statement">When responding to authorized requests, <span rel="spec:requirementSubject" resource="#Server">servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> indicate supported media types in the HTTP <code>Accept-Patch</code> [<cite><a class="bibref" href="#bib-rfc5789">RFC5789</a></cite>], <code>Accept-Post</code> [<cite><a class="bibref" href="#bib-ldp">LDP</a></cite>] and <code>Accept-Put</code> [<cite><a href="#accept-put">The Accept-Put Response Header</a></cite>] response headers that correspond to acceptable HTTP methods listed in <code>Allow</code> header value in response to HTTP <code>GET</code>, <code>HEAD</code> and <code>OPTIONS</code> requests.</span></span></p>

                  <p>[<a href="https://github.com/solid/specification/issues/85#issuecomment-575386251" rel="cito:citesAsSourceDocument">Source</a>] [<a href="https://github.com/solid/specification/issues/43" rel="cito:citesAsSourceDocument">Source</a>] [<a href="https://github.com/solid/specification/pull/378" rel="cito:citesAsSourceDocument">Source</a>]</p>
                </div>
              </section>

              <section id="writing-resources" inlist="" rel="schema:hasPart" resource="#writing-resources">
                <h3 property="schema:name">Writing Resources</h3>
                <div datatype="rdf:HTML" property="schema:description">
                  <p>Servers MUST support the HTTP <code>PUT</code>, <code>POST</code> and <code>PATCH</code> methods [<cite><a class="bibref" href="#bib-rfc7231">RFC7231</a></cite>]. [<a href="https://github.com/solid/specification/issues/39#issuecomment-538017667" rel="cito:citesAsSourceDocument">Source</a>] [<a href="https://github.com/solid/specification/pull/304" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <p><span about="" id="server-put-patch-intermediate-containers" rel="spec:requirement" resource="#server-put-patch-intermediate-containers"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> create intermediate containers and include corresponding containment triples in container representations derived from the URI path component of <code>PUT</code> and <code>PATCH</code> requests.</span></span> [<a href="https://github.com/solid/specification/issues/68#issuecomment-561690124" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <p><span about="" id="server-post-container" rel="spec:requirement" resource="#server-post-container"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> allow creating new resources with a <code>POST</code> request to URI path ending <code>/</code>.</span></span> <span about="" id="server-post-container-create-resource" rel="spec:requirement" resource="#server-post-container-create-resource"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> create a resource with URI path ending <code>/{id}</code> in container <code>/</code>.</span></span> <span about="" id="server-post-container-create-container" rel="spec:requirement" resource="#server-post-container-create-container"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> create a container with URI path ending <code>/{id}/</code> in container <code>/</code> for requests including the HTTP <code>Link</code> header with <code>rel="type"</code> targeting a valid LDP container type.</span></span> [<a href="https://github.com/solid/specification/pull/160#issuecomment-636822687" rel="cito:citesAsSourceDocument">Source</a>] [<a href="https://github.com/solid/specification/pull/190" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <p><span about="" id="server-post-target-not-found" rel="spec:requirement" resource="#server-post-target-not-found"><span property="spec:statement">When a <code>POST</code> method request targets a resource without an existing representation, the <span rel="spec:requirementSubject" resource="#Server">server</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> respond with the <code>404</code> status code.</span></span> [<a href="https://github.com/solid/specification/issues/108#issuecomment-549448159" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <p><span about="" id="server-put-patch-auxiliary-resource" rel="spec:requirement" resource="#server-put-patch-auxiliary-resource"><span property="spec:statement">When a <code>PUT</code> or <code>PATCH</code> method request targets an auxiliary resource, the <span rel="spec:requirementSubject" resource="#Server">server</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> create or update it.</span></span> <span about="" id="server-post-slug-auxiliary-resource" rel="spec:requirement" resource="#server-post-slug-auxiliary-resource"><span property="spec:statement">When a <code>POST</code> method request with the <code>Slug</code> header targets an auxiliary resource, the <span rel="spec:requirementSubject" resource="#Server">server</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> respond with the <code>403</code> status code and response body describing the error.</span></span> [<a href="https://github.com/solid/specification/issues/42#issuecomment-616688848" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <p><span about="" id="server-protect-containment" rel="spec:requirement" resource="#server-protect-containment"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUSTNOT">MUST NOT</span> allow HTTP <code>PUT</code> or <code>PATCH</code> on a container to update its containment triples; if the server receives such a request, it <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> respond with a <code>409</code> status code.</span></span> [<a href="https://github.com/solid/specification/issues/40#issuecomment-573358652" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <p><span about="" id="server-protect-contained-resource-metadata" rel="spec:requirement" resource="#server-protect-contained-resource-metadata"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUSTNOT">MUST NOT</span> allow HTTP <code>POST</code>, <code>PUT</code> and <code>PATCH</code> to update a container’s <a href="#contained-resource-metadata-statements">resource metadata statements</a>; if the server receives such a request, it MUST respond with a <code>409</code> status code.</span></span> [<a href="https://github.com/solid/specification/issues/227#issuecomment-919312592" rel="cito:citesAsSourceDocument">Source</a>]</p>

                  <div class="note" id="conditional-update" inlist="" rel="schema:hasPart" resource="#conditional-update">
                    <h4 property="schema:name"><span>Note</span>: Conditional Update</h4>
                    <div datatype="rdf:HTML" property="schema:description">
                      <p>Clients are encouraged to use the HTTP <code>If-None-Match</code> header with a value of <code>"*"</code> to prevent an unsafe request method, e.g., <code>PUT</code>, <code>PATCH</code>, from inadvertently modifying an existing representation of the target resource when the client believes that the resource does not have a current representation. [<a href="https://github.com/solid/specification/issues/108#issuecomment-567272797" rel="cito:citesAsSourceDocument">Source</a>] [<a href="https://github.com/solid/specification/issues/40#issuecomment-566995240" rel="cito:citesAsSourceDocument">Source</a>] [<a href="https://github.com/solid/specification/pull/292" rel="cito:citesAsSourceDocument">Source</a>]</p>
                    </div>
                  </div>

                  <p><span about="" id="server-etag" rel="spec:requirement" resource="#server-etag"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MAY">MAY</span> use the HTTP <code>ETag</code> header with a strong validator for RDF bearing representations in order to encourage clients to opt-in to using the <code>If-Match</code> header in their requests.</span></span></p>
                </div>

                <section id="n3-patch" inlist="" rel="schema:hasPart" resource="#n3-patch">
                  <h4 property="schema:name">Modifying Resources Using N3 Patches</h4>
                  <div datatype="rdf:HTML" property="schema:description">
                    <p><span about="" id="server-patch-n3-accept" rel="spec:requirement" resource="#server-patch-n3-accept"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> accept a <code>PATCH</code> request with an <em>N3 Patch</em> body when the target of the request is an <em>RDF document</em> [<cite><a class="bibref" href="#bib-rdf11-concepts">RDF11-CONCEPTS</a></cite>].</span></span> <span about="" id="server-patch-n3-advertise" rel="spec:requirement" resource="#server-patch-n3-advertise"><span property="spec:statement"><span rel="spec:requirementSubject" resource="#Server">Servers</span> <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> indicate support of N3 Patch by listing <code>text/n3</code> as a value of the <code>Accept-Patch</code> header [<cite><a class="bibref" href="#bib-rfc5789">RFC5789</a></cite>] of relevant responses.</span></span> [<a href="https://github.com/solid/specification/issues/125#issuecomment-959518598" rel="cito:citesAsSourceDocument">Source</a>]</p>

                    <p>An <em>N3 Patch</em> is a document in the <em>Notation3 (N3)</em> format [<cite><a class="bibref" href="#bib-notation3">N3</a></cite>], identified by the media type <code>text/n3</code>, conforming to the following constraints:</p>

                    <ul>
                      <li id="server-patch-n3-patches" rel="spec:requirement" resource="#server-patch-n3-patches"><span property="spec:statement">A patch document <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> contain one or more patch resources.</span></li>
                      <li id="server-patch-n3-patch-identifier" rel="spec:requirement" resource="#server-patch-n3-patch-identifier"><span property="spec:statement">A patch resource <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> be identified by a URI or blank node, which we refer to as <code>?patch</code> in the remainder of this section.</span></li>
                      <li id="server-patch-n3-type" rel="spec:requirement" resource="#server-patch-n3-type">A patch resource <span rel="spec:requirementLevel" resource="spec:MAY">MAY</span> contain a triple [<cite><a class="bibref" href="#bib-rdf11-concepts">RDF11-CONCEPTS</a></cite>] <code><span property="spec:statement">?patch rdf:type solid:Patch</span></code>.</li>
                      <li id="server-patch-n3-deletes" rel="spec:requirement" resource="#server-patch-n3-deletes"><span property="spec:statement">A patch resource <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> contain at most one triple of the form <code>?patch solid:deletes ?deletions</code>.</span></li>
                      <li id="server-patch-n3-inserts" rel="spec:requirement" resource="#server-patch-n3-inserts">A patch resource <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> contain at most one triple of the form <code>?patch solid:inserts ?insertions</code>.</li>
                      <li id="server-patch-n3-where" rel="spec:requirement" resource="#server-patch-n3-where"><span property="spec:statement">A patch resource <span rel="spec:requirementLevel" resource="spec:MUST">MUST</span> contain at most one triple of the form <code>?patch solid:where ?conditions</code>.</span></li>