did-resolution/ED-did-resolution-20250109.html at main · w3c/did-resolution · GitHub

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      "title": "Architectural Styles and the Design of Network-based Software Architectures",
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      "href": "http://www.ics.uci.edu/~fielding/pubs/dissertation/",
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      "url": "https://www.linkedin.com/in/dzagidulin",
      "company": "MIT CSAIL",
      "companyURL": "http://computingjoy.com/",
      "w3cid": 86708
    }
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      "company": "MIT CSAIL",
      "companyURL": "http://computingjoy.com/",
      "w3cid": 86708
    }
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<link rel="stylesheet" href="https://www.w3.org/StyleSheets/TR/2021/W3C-ED"></head>
  <body data-cite="infra rfc3986" class="h-entry"><div class="head">
    <p class="logos"><a class="logo" href="https://www.w3.org/"><img crossorigin="" alt="W3C" height="48" src="https://www.w3.org/StyleSheets/TR/2021/logos/W3C" width="72">
  </a></p>
    <h1 id="title" class="title">Decentralized Identifier Resolution (DID Resolution) v0.3</h1> <h2 id="subtitle" class="subtitle">Algorithms and guidelines for resolving DIDs and dereferencing DID URLs</h2>
    <p id="w3c-state"><a href="https://www.w3.org/standards/types#ED">W3C Editor's Draft</a> <time class="dt-published" datetime="2025-01-09">09 January 2025</time></p>
    <details open="">
      <summary>More details about this document</summary>
      <dl>
        <dt>This version:</dt><dd>
                <a class="u-url" href="https://w3c.github.io/did-resolution/">https://w3c.github.io/did-resolution/</a>
              </dd>
        <dt>Latest published version:</dt><dd>
                <a href="https://www.w3.org/TR/did-resolution/">https://www.w3.org/TR/did-resolution/</a>
              </dd>
        <dt>Latest editor's draft:</dt><dd><a href="https://w3c.github.io/did-resolution/">https://w3c.github.io/did-resolution/</a></dd>
        <dt>History:</dt><dd>
                    <a href="https://www.w3.org/standards/history/did-resolution/">https://www.w3.org/standards/history/did-resolution/</a>
                  </dd><dd>
                    <a href="https://github.com/w3c/did-resolution/commits/">Commit history</a>
                  </dd>


        <dt>Editors:</dt><dd class="editor p-author h-card vcard" data-editor-id="46729">
    <a class="u-url url p-name fn" href="https://www.linkedin.com/in/markus-sabadello-353a0821">Markus Sabadello</a> (<a class="p-org org h-org" href="https://danubetech.com/">Danube Tech</a>)
  </dd><dd class="editor p-author h-card vcard" data-editor-id="86708">
    <a class="u-url url p-name fn" href="https://www.linkedin.com/in/dzagidulin">Dmitri Zagidulin</a> (<a class="p-org org h-org" href="http://computingjoy.com/">MIT CSAIL</a>)
  </dd>

        <dt>Authors:</dt><dd class="editor p-author h-card vcard" data-editor-id="46729">
    <a class="u-url url p-name fn" href="https://www.linkedin.com/in/markus-sabadello-353a0821">Markus Sabadello</a> (<a class="p-org org h-org" href="https://danubetech.com/">Danube Tech</a>)
  </dd><dd class="editor p-author h-card vcard" data-editor-id="86708">
    <a class="u-url url p-name fn" href="https://www.linkedin.com/in/dzagidulin">Dmitri Zagidulin</a> (<a class="p-org org h-org" href="http://computingjoy.com/">MIT CSAIL</a>)
  </dd>
        <dt>Feedback:</dt><dd>
        <a href="https://github.com/w3c/did-resolution/">GitHub w3c/did-resolution</a>
        (<a href="https://github.com/w3c/did-resolution/pulls/">pull requests</a>,
        <a href="https://github.com/w3c/did-resolution/issues/new/choose">new issue</a>,
        <a href="https://github.com/w3c/did-resolution/issues/">open issues</a>)
      </dd><dd><a href="mailto:public-did-wg@w3.org?subject=%5Bdid-resolution%5D%20YOUR%20TOPIC%20HERE">public-did-wg@w3.org</a> with subject line <kbd>[did-resolution] <em>… message topic …</em></kbd> (<a rel="discussion" href="https://lists.w3.org/Archives/Public/public-did-wg">archives</a>)</dd>


      </dl>
    </details>


    <p class="copyright">
    <a href="https://www.w3.org/policies/#copyright">Copyright</a>
    ©
    2025

    <a href="https://www.w3.org/">World Wide Web Consortium</a>.
    <abbr title="World Wide Web Consortium">W3C</abbr><sup>®</sup>
    <a href="https://www.w3.org/policies/#Legal_Disclaimer">liability</a>,
    <a href="https://www.w3.org/policies/#W3C_Trademarks">trademark</a> and
    <a rel="license" href="https://www.w3.org/copyright/software-license-2023/" title="W3C Software and Document Notice and License">permissive document license</a> rules apply.
  </p>
    <hr title="Separator for header">
  </div>
    <section id="abstract" class="introductory"><h2>Abstract</h2>
      <p>
Decentralized identifiers (DIDs) are a new type of identifier for
verifiable, "self-sovereign" digital identity. DIDs are fully under the
control of the DID controller, independent from any centralized registry,
identity provider, or certificate authority. DIDs resolve to DID
Documents — simple documents that describe how to use that specific DID.
      </p>

      <p>
This document specifies the algorithms and guidelines for resolving DIDs
and dereferencing DID URLs.
      </p>
    </section>

    <section id="sotd" class="introductory"><h2>Status of This Document</h2><p><em>This section describes the status of this
      document at the time of its publication. A list of current <abbr title="World Wide Web Consortium">W3C</abbr>
      publications and the latest revision of this technical report can be found
      in the <a href="https://www.w3.org/TR/"><abbr title="World Wide Web Consortium">W3C</abbr> technical reports index</a> at
      https://www.w3.org/TR/.</em></p>
    <p>
      Comments regarding this document are welcome. Please file issues
      directly on <a href="https://github.com/w3c/did-resolution/issues/">GitHub</a>,
      or send them to
      <a href="mailto:public-did-wg@w3.org">public-did-wg@w3.org</a>
      (<a href="mailto:public-did-wg-request@w3.org?subject=subscribe">subscribe</a>,
      <a href="https://lists.w3.org/Archives/Public/public-did-wg/">archives</a>).
      </p>

      <p>
      Portions of the work on this specification have been funded by the
      United States Department of Homeland Security's Science and Technology
      Directorate under contracts HSHQDC-17-C-00019. The content of this
      specification does not necessarily reflect the position or the policy of
      the U.S. Government and no official endorsement should be inferred.
      </p>

      <p>
      Work on this specification has also been supported by the Rebooting the
      Web of Trust community facilitated by Christopher Allen, Shannon
      Appelcline, Kiara Robles, Brian Weller, Betty Dhamers, Kaliya Young, Kim
      Hamilton Duffy, Manu Sporny, Drummond Reed, Joe Andrieu, and Heather
      Vescent.
      </p>
    <p>
    This document was published by the <a href="https://www.w3.org/groups/wg/did">Decentralized Identifier Working Group</a> as
    an Editor's Draft.
  </p><p>Publication as an Editor's Draft does not
  imply endorsement by <abbr title="World Wide Web Consortium">W3C</abbr> and its Members. </p><p>
    This is a draft document and 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/policies/patent-policy/"><abbr title="World Wide Web Consortium">W3C</abbr> Patent
          Policy</a>.


                <abbr title="World Wide Web Consortium">W3C</abbr> maintains a
                <a rel="disclosure" href="https://www.w3.org/groups/wg/did/ipr">public list of any patent disclosures</a>
          made in connection with the deliverables of
          the group; that page also includes
          instructions for disclosing a patent. An individual who has actual
          knowledge of a patent which the individual believes contains
          <a href="https://www.w3.org/policies/patent-policy/#def-essential">Essential Claim(s)</a>
          must disclose the information in accordance with
          <a href="https://www.w3.org/policies/patent-policy/#sec-Disclosure">section 6 of the <abbr title="World Wide Web Consortium">W3C</abbr> Patent Policy</a>.

  </p><p>
                      This document is governed by the
                      <a id="w3c_process_revision" href="https://www.w3.org/policies/process/20231103/">03 November 2023 <abbr title="World Wide Web Consortium">W3C</abbr> Process Document</a>.
                    </p></section><nav id="toc"><h2 class="introductory" id="table-of-contents">Table of Contents</h2><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"><bdi class="secno">1. </bdi>Introduction</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#conformance"><bdi class="secno">1.1 </bdi>Conformance</a></li></ol></li><li class="tocline"><a class="tocxref" href="#terminology"><bdi class="secno">2. </bdi>Terminology</a></li><li class="tocline"><a class="tocxref" href="#resolving"><bdi class="secno">3. </bdi>DID Resolution</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#did-resolution-options"><bdi class="secno">3.1 </bdi>DID Resolution Options</a></li><li class="tocline"><a class="tocxref" href="#did-resolution-metadata"><bdi class="secno">3.2 </bdi>DID Resolution Metadata</a></li><li class="tocline"><a class="tocxref" href="#did-document-metadata"><bdi class="secno">3.3 </bdi>DID Document Metadata</a></li><li class="tocline"><a class="tocxref" href="#resolving-algorithm"><bdi class="secno">3.4 </bdi>Algorithm</a></li></ol></li><li class="tocline"><a class="tocxref" href="#dereferencing"><bdi class="secno">4. </bdi>DID URL Dereferencing</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#did-url-dereferencing-options"><bdi class="secno">4.1 </bdi>DID URL Dereferencing Options</a></li><li class="tocline"><a class="tocxref" href="#did-url-dereferencing-metadata"><bdi class="secno">4.2 </bdi>DID URL Dereferencing Metadata</a></li><li class="tocline"><a class="tocxref" href="#dereferencing-algorithm"><bdi class="secno">4.3 </bdi>Algorithm</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#dereferencing-algorithm-resource"><bdi class="secno">4.3.1 </bdi>Dereferencing the Resource</a></li><li class="tocline"><a class="tocxref" href="#dereferencing-algorithm-fragment"><bdi class="secno">4.3.2 </bdi>Dereferencing the Fragment</a></li></ol></li><li class="tocline"><a class="tocxref" href="#examples"><bdi class="secno">4.4 </bdi>Examples</a></li></ol></li><li class="tocline"><a class="tocxref" href="#metadata-structure"><bdi class="secno">5. </bdi>Metadata Structure</a></li><li class="tocline"><a class="tocxref" href="#architectures"><bdi class="secno">6. </bdi>DID Resolution Architectures</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#method-architectures"><bdi class="secno">6.1 </bdi>Method Architectures</a></li><li class="tocline"><a class="tocxref" href="#resolver-architectures"><bdi class="secno">6.2 </bdi>Resolver Architectures</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#resolver-architectures-proxied"><bdi class="secno">6.2.1 </bdi>Proxied Resolution</a></li><li class="tocline"><a class="tocxref" href="#resolver-architectures-client-side"><bdi class="secno">6.2.2 </bdi>Client-Side Dereferencing</a></li></ol></li></ol></li><li class="tocline"><a class="tocxref" href="#did-resolution-result"><bdi class="secno">7. </bdi>DID Resolution Result</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#example"><bdi class="secno">7.1 </bdi>Example</a></li><li class="tocline"><a class="tocxref" href="#output-diddocument"><bdi class="secno">7.2 </bdi>DID Document</a></li><li class="tocline"><a class="tocxref" href="#output-resolutionmetadata"><bdi class="secno">7.3 </bdi>DID Resolution Metadata</a></li><li class="tocline"><a class="tocxref" href="#output-documentmetadata"><bdi class="secno">7.4 </bdi>DID Document Metadata</a></li></ol></li><li class="tocline"><a class="tocxref" href="#did-url-dereferencing-result"><bdi class="secno">8. </bdi>DID URL Dereferencing Result</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#example-0"><bdi class="secno">8.1 </bdi>Example</a></li><li class="tocline"><a class="tocxref" href="#output-content"><bdi class="secno">8.2 </bdi>Content</a></li><li class="tocline"><a class="tocxref" href="#output-dereferencingmetadata"><bdi class="secno">8.3 </bdi>DID URL Dereferencing Metadata</a></li><li class="tocline"><a class="tocxref" href="#output-contentmetadata"><bdi class="secno">8.4 </bdi>Content Metadata</a></li></ol></li><li class="tocline"><a class="tocxref" href="#errors"><bdi class="secno">9. </bdi>Errors</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#invaliddid"><bdi class="secno">9.1 </bdi>invalidDid</a></li><li class="tocline"><a class="tocxref" href="#invaliddidurl"><bdi class="secno">9.2 </bdi>invalidDidUrl</a></li><li class="tocline"><a class="tocxref" href="#notfound"><bdi class="secno">9.3 </bdi>notFound</a></li><li class="tocline"><a class="tocxref" href="#representationnotsupported"><bdi class="secno">9.4 </bdi>representationNotSupported</a></li><li class="tocline"><a class="tocxref" href="#methodnotsupported"><bdi class="secno">9.5 </bdi>methodNotSupported</a></li><li class="tocline"><a class="tocxref" href="#internalerror"><bdi class="secno">9.6 </bdi>internalError</a></li><li class="tocline"><a class="tocxref" href="#invalidpublickey"><bdi class="secno">9.7 </bdi>invalidPublicKey</a></li><li class="tocline"><a class="tocxref" href="#invalidpublickeylength"><bdi class="secno">9.8 </bdi>invalidPublicKeyLength</a></li><li class="tocline"><a class="tocxref" href="#invalidpublickeytype"><bdi class="secno">9.9 </bdi>invalidPublicKeyType</a></li><li class="tocline"><a class="tocxref" href="#unsupportedpublickeytype"><bdi class="secno">9.10 </bdi>unsupportedPublicKeyType</a></li></ol></li><li class="tocline"><a class="tocxref" href="#bindings"><bdi class="secno">10. </bdi>Bindings</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#bindings-https"><bdi class="secno">10.1 </bdi>HTTP(S) Binding</a></li><li class="tocline"><a class="tocxref" href="#did-resolution-examples"><bdi class="secno">10.2 </bdi>DID Resolution Examples</a></li><li class="tocline"><a class="tocxref" href="#did-url-dereferencing-examples"><bdi class="secno">10.3 </bdi>DID URL Dereferencing Examples</a></li></ol></li><li class="tocline"><a class="tocxref" href="#service-endpoint-construction"><bdi class="secno">11. </bdi>Service Endpoint Construction</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#input"><bdi class="secno">11.1 </bdi>Input</a></li><li class="tocline"><a class="tocxref" href="#algorithm"><bdi class="secno">11.2 </bdi>Algorithm</a></li><li class="tocline"><a class="tocxref" href="#example-10"><bdi class="secno">11.3 </bdi>Example</a></li></ol></li><li class="tocline"><a class="tocxref" href="#security-privacy-considerations"><bdi class="secno">12. </bdi>Security and Privacy Considerations</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#authentication"><bdi class="secno">12.1 </bdi>Authentication/Authorization</a></li><li class="tocline"><a class="tocxref" href="#caching"><bdi class="secno">12.2 </bdi>Caching</a></li><li class="tocline"><a class="tocxref" href="#versioning"><bdi class="secno">12.3 </bdi>Versioning</a></li><li class="tocline"><a class="tocxref" href="#non-did-identifiers"><bdi class="secno">12.4 </bdi>Non-DID Identifiers</a></li><li class="tocline"><a class="tocxref" href="#did-method-governance"><bdi class="secno">12.5 </bdi>DID Method Governance</a></li></ol></li><li class="tocline"><a class="tocxref" href="#future-work"><bdi class="secno">13. </bdi>Future Work</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#redirect"><bdi class="secno">13.1 </bdi>Redirect</a></li><li class="tocline"><a class="tocxref" href="#proxy"><bdi class="secno">13.2 </bdi>Proxy</a></li><li class="tocline"><a class="tocxref" href="#json-pointer"><bdi class="secno">13.3 </bdi>JSON Pointer</a></li></ol></li><li class="tocline"><a class="tocxref" href="#did-resolution-resources"><bdi class="secno">A. </bdi>DID Resolution Resources</a></li><li class="tocline"><a class="tocxref" href="#references"><bdi class="secno">B. </bdi>References</a><ol class="toc"><li class="tocline"><a class="tocxref" href="#normative-references"><bdi class="secno">B.1 </bdi>Normative references</a></li><li class="tocline"><a class="tocxref" href="#informative-references"><bdi class="secno">B.2 </bdi>Informative references</a></li></ol></li></ol></nav>

<section id="introduction"><div class="header-wrapper"><h2 id="x1-introduction"><bdi class="secno">1. </bdi>Introduction</h2><a class="self-link" href="#introduction" aria-label="Permalink for Section 1."></a></div>


	<p><a href="#dfn-did-resolution" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolution-1">DID resolution</a> is the process of obtaining a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-1">DID document</a> for a given <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-1">DID</a>. This is one
	of four required operations that can be performed on any DID ("Read"; the other ones being "Create", "Update",
	and "Deactivate"). The details of these operations differ depending on the <a href="#dfn-did-method-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-method-s-1">DID method</a>.
	Building on top of <a href="#dfn-did-resolution" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolution-2">DID resolution</a>, <a href="#dfn-did-url-dereferencing" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-url-dereferencing-1">DID URL dereferencing</a> is the process of retrieving a representation
	of a resource for a given <a href="#dfn-did-urls" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-urls-1">DID URL</a>. Software and/or hardware that is able to execute these processes is called
	a <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-1">DID resolver</a>.

	</p><p>This
	specification defines common
	requirements, algorithms including their inputs and results, architectural options, and various considerations for the
	<a href="#dfn-did-resolution" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolution-3">DID resolution</a> and <a href="#dfn-did-url-dereferencing" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-url-dereferencing-2">DID URL dereferencing</a> processes.</p>

	<p>Note that while this specification defines some base-level functionality for DID resolution, the actual steps
	required to communicate with a DID's <a href="#dfn-verifiable-data-registry" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-verifiable-data-registry-1">verifiable data registry</a> are defined by the applicable
	<a href="#dfn-did-method-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-method-s-2">DID method</a> specification.</p>

	<div class="note" role="note" id="issue-container-generatedID"><div role="heading" class="note-title marker" id="h-note" aria-level="3"><span>Note</span></div><p class="">The difference between "resolving" a <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-2">DID</a> and "dereferencing" a <a href="#dfn-did-urls" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-urls-2">DID URL</a>
	is being thoroughly discussed by the community. For example, see
	<a href="https://github.com/w3c/did-spec/issues/166#issuecomment-464502719">this comment</a>.</p></div>

	<section id="conformance"><div class="header-wrapper"><h3 id="x1-1-conformance"><bdi class="secno">1.1 </bdi>Conformance</h3><a class="self-link" href="#conformance" aria-label="Permalink for Section 1.1"></a></div><p>As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.</p><p>
        The key words <em class="rfc2119">MAY</em>, <em class="rfc2119">MUST</em>, <em class="rfc2119">MUST NOT</em>, <em class="rfc2119">OPTIONAL</em>, <em class="rfc2119">RECOMMENDED</em>, <em class="rfc2119">REQUIRED</em>, and <em class="rfc2119">SHOULD</em> in this document
        are to be interpreted as described in
        <a href="https://datatracker.ietf.org/doc/html/bcp14">BCP 14</a>
        [<cite><a class="bibref" data-link-type="biblio" href="#bib-rfc2119" title="Key words for use in RFCs to Indicate Requirement Levels">RFC2119</a></cite>] [<cite><a class="bibref" data-link-type="biblio" href="#bib-rfc8174" title="Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words">RFC8174</a></cite>]
        when, and only when, they appear in all capitals, as shown here.
      </p>

		<p>
			A <dfn class="lint-ignore" id="dfn-conforming-did-resolver" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">conforming DID resolver</dfn> is any algorithm
			realized as software and/or hardware that complies with the relevant normative
			statements in <a href="#resolving" class="sec-ref"><bdi class="secno">3. </bdi>DID Resolution</a>.
		</p>

		<p>
			A <dfn class="lint-ignore" id="dfn-conforming-did-url-dereferencer" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">conforming DID URL dereferencer</dfn> is any
			algorithm realized as software and/or hardware that complies with the relevant
			normative statements in <a href="#dereferencing" class="sec-ref"><bdi class="secno">4. </bdi>DID URL Dereferencing</a>.
		</p>

	</section>

</section>

<section id="terminology"><div class="header-wrapper"><h2 id="x2-terminology"><bdi class="secno">2. </bdi>Terminology</h2><a class="self-link" href="#terminology" aria-label="Permalink for Section 2."></a></div>


	<div><p>
This section defines the terms used in this specification and throughout
<a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-3">decentralized identifier</a> infrastructure. A link to these terms is
included whenever they appear in this specification.
</p>

<dl class="termlist">

  <dt><dfn data-lt="authenticated|authenticate" id="dfn-authenticated" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">authenticate</dfn></dt>
  <dd>
    Authentication is a process by which an entity can prove it has a specific
    attribute or controls a specific secret using one or more <a href="#dfn-verification-method" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-verification-method-1">verification
    methods</a>. With <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-4">DIDs</a>, a common example would be proving control of the
    cryptographic private key associated with a public key published in a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-2">DID
    document</a>.
  </dd>

  <dt><dfn data-plurals="bindings" id="dfn-binding" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">binding</dfn></dt>
  <dd>A concrete mechanism through which a <a href="#dfn-client" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-client-1">client</a> invokes a <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-2">DID resolver</a>. This could be a <a href="#dfn-local-binding" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-local-binding-1">local binding</a> such as a local command line tool or library API, or a <a href="#dfn-remote-binding" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-remote-binding-1">remote binding</a> such as the <a href="#bindings-https">HTTP(S) binding</a>. See Section <a href="#resolver-architectures" class="sec-ref"><bdi class="secno">6.2 </bdi>Resolver Architectures</a>.</dd>

  <dt><dfn id="dfn-client" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">client</dfn></dt>
  <dd>Software and/or hardware that invokes a <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-3">DID resolver</a> in order to execute the <a href="#dfn-did-resolution" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolution-4">DID resolution</a> and/or <a href="#dfn-did-url-dereferencing" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-url-dereferencing-3">DID URL dereferencing</a> algorithms. This invocation is done via a <a href="#dfn-binding" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-binding-1">binding</a>. The term <a href="#dfn-client" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-client-2">client</a> does not imply any specific network topology.</dd>

  <dt><dfn data-lt="decentralized identifiers|DID|DIDs|decentralized identifier" data-plurals="dids|did" id="dfn-decentralized-identifiers" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">decentralized identifier</dfn> (DID)</dt>
  <dd>
    A globally unique persistent identifier that does not require a centralized
    registration authority and is often generated and/or registered
    cryptographically. The generic format of a DID is defined in <a href="https://w3c.github.io/did-core/#did-syntax"></a>. A specific <a href="#dfn-did-schemes" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-schemes-1">DID scheme</a> is defined in a <a href="#dfn-did-method-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-method-s-3">DID
    method</a> specification. Many—but not all—DID methods make use of
    <a href="#dfn-distributed-ledger-technology" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-distributed-ledger-technology-1">distributed ledger technology</a> (DLT) or some other form of decentralized
    network.
  </dd>

  <dt><dfn data-lt="did controllers|did controller(s)|DID controller" id="dfn-did-controllers" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID controller</dfn></dt>
  <dd>
    An entity that has the capability to make changes to a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-3">DID document</a>. A
    <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-5">DID</a> might have more than one DID controller. The DID controller(s)
    can be denoted by the optional <code>controller</code> property at the top level of the
    <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-4">DID document</a>. Note that a DID controller might be the <a href="#dfn-did-subjects" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-subjects-1">DID
    subject</a>.
  </dd>

  <dt><dfn id="dfn-did-delegate" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID delegate</dfn></dt>
  <dd>
    An entity to whom a <a href="#dfn-did-controllers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-controllers-1">DID controller</a> has granted permission to use a
    <a href="#dfn-verification-method" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-verification-method-2">verification method</a> associated with a <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-6">DID</a> via a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-5">DID
    document</a>. For example, a parent who controls a child's <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-6">DID document</a>
    might permit the child to use their personal device in order to
    <a href="#dfn-authenticated" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-authenticated-1">authenticate</a>. In this case, the child is the <a href="#dfn-did-delegate" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-delegate-1">DID delegate</a>. The
    child's personal device would contain the private cryptographic material
    enabling the child to <a href="#dfn-authenticated" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-authenticated-2">authenticate</a> using the <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-7">DID</a>. However, the child
    might not be permitted to add other personal devices without the parent's
    permission.
  </dd>

  <dt><dfn data-lt="DID documents|DID document" data-plurals="did documents" id="dfn-did-documents" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID document</dfn></dt>
  <dd>
    A set of data describing the <a href="#dfn-did-subjects" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-subjects-2">DID subject</a>, including mechanisms, such as
    cryptographic public keys, that the <a href="#dfn-did-subjects" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-subjects-3">DID subject</a> or a <a href="#dfn-did-delegate" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-delegate-2">DID delegate</a>
    can use to <a href="#dfn-authenticated" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-authenticated-3">authenticate</a> itself and prove its association with the
    <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-8">DID</a>.
  </dd>

  <dt><dfn data-lt="DID fragments|DID fragment" id="dfn-did-fragments" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID fragment</dfn></dt>
  <dd>
    The portion of a <a href="#dfn-did-urls" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-urls-3">DID URL</a> that follows the first hash sign character
    (<code>#</code>). DID fragment syntax is identical to URI fragment syntax.
  </dd>

  <dt><dfn data-lt="DID method's|DID method" data-plurals="did methods" id="dfn-did-method-s" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID method</dfn></dt>
  <dd>
    A definition of how a specific <a href="#dfn-did-schemes" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-schemes-2">DID method scheme</a> is implemented. A DID method is
    defined by a DID method specification, which specifies the precise operations by
    which <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-9">DIDs</a> and <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-7">DID documents</a> are created, resolved, updated,
    and deactivated. See <a href="https://w3c.github.io/did-core/#methods"></a>.
  </dd>

  <dt><dfn data-lt="DID paths|DID path" id="dfn-did-paths" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID path</dfn></dt>
  <dd>
    The portion of a <a href="#dfn-did-urls" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-urls-4">DID URL</a> that begins with and includes the first forward
    slash (<code>/</code>) character and ends with either a question mark
    (<code>?</code>) character, a fragment hash sign (<code>#</code>) character,
    or the end of the <a href="#dfn-did-urls" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-urls-5">DID URL</a>. DID path syntax is identical to URI path syntax.
    See <a href="https://w3c.github.io/did-core/#path"></a>.
  </dd>

  <dt><dfn data-lt="DID queries|DID query" id="dfn-did-queries" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID query</dfn></dt>
  <dd>
    The portion of a <a href="#dfn-did-urls" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-urls-6">DID URL</a> that follows and includes the first question
    mark character (<code>?</code>). DID query syntax is identical to URI query
    syntax. See <a href="https://w3c.github.io/did-core/#query"></a>.
  </dd>

  <dt><dfn id="dfn-did-resolution" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID resolution</dfn></dt>
  <dd>
    The process that takes as its input a <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-10">DID</a> and a set of resolution
    options and returns a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-8">DID document</a> in a conforming <a href="#dfn-representations" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-representations-1">representation</a>
    plus additional metadata. This process relies on the "Read" operation of the
    applicable <a href="#dfn-did-method-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-method-s-4">DID method</a>. The inputs and outputs of this process are
    defined in <a href="#resolving" class="sec-ref"><bdi class="secno">3. </bdi>DID Resolution</a>.
  </dd>

  <dt><dfn data-lt="DID resolver's|DID resolver" data-plurals="did resolvers" id="dfn-did-resolver-s" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID resolver</dfn></dt>
  <dd>
    A <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-4">DID resolver</a> is a software and/or hardware component that performs the
    <a href="#dfn-did-resolution" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolution-5">DID resolution</a> function by taking a <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-11">DID</a> as input and producing a
    conforming <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-9">DID document</a> as output.
  </dd>

  <dt><dfn data-lt="" id="dfn-did-resolution-result" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID resolution result</dfn></dt>
  <dd>A data structure that represents the result of the <a href="#dfn-did-resolution" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolution-6">DID resolution</a> algorithm.
    May contain a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-10">DID document</a>. See Section <a href="#did-resolution-result" class="sec-ref"><bdi class="secno">7. </bdi>DID Resolution Result</a>.</dd>

  <dt><dfn data-lt="DID schemes|DID method scheme|DID scheme" id="dfn-did-schemes" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID scheme</dfn></dt>

  <dd>
    The formal syntax of a <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-12">decentralized identifier</a>. The generic DID scheme
    begins with the prefix <code>did:</code> as defined in <a href="https://w3c.github.io/did-core/#did-syntax"></a>. Each <a href="#dfn-did-method-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-method-s-5">DID method</a> specification defines a specific
    DID method scheme that works with that specific <a href="#dfn-did-method-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-method-s-6">DID method</a>. In a specific DID
    method scheme, the DID method name follows the first colon and terminates with
    the second colon, e.g., <code>did:example:</code>
  </dd>

  <dt><dfn data-lt="DID subjects|DID subject" id="dfn-did-subjects" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID subject</dfn></dt>

  <dd>
    The entity identified by a <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-13">DID</a> and described by a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-11">DID document</a>.
    Anything can be a DID subject: person, group, organization, physical thing,
    digital thing, logical thing, etc.
  </dd>

  <dt><dfn data-lt="DID URLs|DID URL" id="dfn-did-urls" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID URL</dfn></dt>
  <dd>
    A <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-14">DID</a> plus any additional syntactic component that conforms to the
    definition in <a href="https://w3c.github.io/did-core/#did-url-syntax"></a>. This includes an optional <a href="#dfn-did-paths" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-paths-1">DID
    path</a> (with its leading <code>/</code> character), optional <a href="#dfn-did-queries" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-queries-1">DID query</a>
    (with its leading <code>?</code> character), and optional <a href="#dfn-did-fragments" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-fragments-1">DID fragment</a>
    (with its leading <code>#</code> character).
  </dd>

  <dt><dfn id="dfn-did-url-dereferencing" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID URL dereferencing</dfn></dt>
  <dd>
    The process that takes as its input a <a href="#dfn-did-urls" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-urls-7">DID URL</a> and a set of input
    metadata, and returns a <a href="#dfn-resources" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-resources-1">resource</a>. This resource might be a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-12">DID
    document</a> plus additional metadata, a secondary resource
    contained within the <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-13">DID document</a>, or a resource entirely
    external to the <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-14">DID document</a>. The process uses <a href="#dfn-did-resolution" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolution-7">DID resolution</a> to
    fetch a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-15">DID document</a> indicated by the <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-15">DID</a> contained within the
    <a href="#dfn-did-urls" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-urls-8">DID URL</a>. The dereferencing process can then perform additional processing
    on the <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-16">DID document</a> to return the dereferenced resource indicated by the
    <a href="#dfn-did-urls" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-urls-9">DID URL</a>. The inputs and outputs of this process are defined in
    <a href="#dereferencing" class="sec-ref"><bdi class="secno">4. </bdi>DID URL Dereferencing</a>.
  </dd>

  <dt><dfn data-lt="DID URL dereferencers|DID URL dereferencer" id="dfn-did-url-dereferencers" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID URL dereferencer</dfn></dt>
  <dd>
    A software and/or hardware system that performs the <a href="#dfn-did-url-dereferencing" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-url-dereferencing-4">DID URL dereferencing</a>
    function for a given <a href="#dfn-did-urls" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-urls-10">DID URL</a> or <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-17">DID document</a>.
  </dd>

  <dt><dfn data-lt="" id="dfn-did-url-dereferencing-result" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">DID URL dereferencing result</dfn></dt>
  <dd>A data structure that represents the result of the <a href="#dfn-did-url-dereferencing" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-url-dereferencing-5">DID URL dereferencing</a> algorithm.
    May contain a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-18">DID document</a> or other content. See Section <a href="#did-url-dereferencing-result" class="sec-ref"><bdi class="secno">8. </bdi>DID URL Dereferencing Result</a>.</dd>

  <dt><dfn data-lt="distributed ledger technology|DLT|distributed ledger" id="dfn-distributed-ledger-technology" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">distributed ledger</dfn> (DLT)</dt>
  <dd>
    A non-centralized system for recording events. These systems establish
    sufficient confidence for participants to rely upon the data recorded by others
    to make operational decisions. They typically use distributed databases where
    different nodes use a consensus protocol to confirm the ordering of
    cryptographically signed transactions. The linking of digitally signed
    transactions over time often makes the history of the ledger effectively
    immutable.
  </dd>

  <dt><dfn data-lt="resources|resource" id="dfn-resources" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">resource</dfn></dt>
  <dd>
    As defined by [<cite><a class="bibref" data-link-type="biblio" href="#bib-rfc3986" title="Uniform Resource Identifier (URI): Generic Syntax">RFC3986</a></cite>]: "...the term 'resource' is used in a general sense
    for whatever might be identified by a URI." Similarly, any resource might serve
    as a <a href="#dfn-did-subjects" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-subjects-4">DID subject</a> identified by a <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-16">DID</a>.
  </dd>

  <dt><dfn data-lt="representations|representation" id="dfn-representations" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">representation</dfn></dt>
  <dd>
    As defined for HTTP by [<cite><a class="bibref" data-link-type="biblio" href="#bib-rfc7231" title="Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content">RFC7231</a></cite>]: "information that is intended to reflect a
    past, current, or desired state of a given resource, in a format that can be
    readily communicated via the protocol, and that consists of a set of
    representation metadata and a potentially unbounded stream of representation
    data." A <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-19">DID document</a> is a representation of information describing a
    <a href="#dfn-did-subjects" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-subjects-5">DID subject</a>. See <a href="https://w3c.github.io/did-core/#representations"></a>.
  </dd>

  <dt><dfn data-lt="" data-plurals="local bindings" id="dfn-local-binding" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">local binding</dfn></dt>
  <dd>A <a href="#dfn-binding" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-binding-2">binding</a> where the <a href="#dfn-client" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-client-3">client</a> invokes a <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-5">DID resolver</a> that runs on the same network host, e.g., via a local command line tool or library API.
    In this case, the <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-6">DID resolver</a> is sometimes also called a "local <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-7">DID resolver</a>".
    See Section <a href="#resolver-architectures" class="sec-ref"><bdi class="secno">6.2 </bdi>Resolver Architectures</a>.</dd>

  <dt><dfn data-lt="" data-plurals="remote bindings" id="dfn-remote-binding" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">remote binding</dfn></dt>
  <dd>A <a href="#dfn-binding" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-binding-3">binding</a> where the <a href="#dfn-client" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-client-4">client</a> invokes a <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-8">DID resolver</a> that runs on a different network host, e.g., via the <a href="#bindings-https">HTTP(S) binding</a>.
    In this case, the <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-9">DID resolver</a> is sometimes also called a "remote <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-10">DID resolver</a>".
    See Section <a href="#resolver-architectures" class="sec-ref"><bdi class="secno">6.2 </bdi>Resolver Architectures</a>.</dd>

  <dt><dfn data-lt="service|services" id="dfn-service" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">services</dfn></dt>
  <dd>
    Means of communicating or interacting with the <a href="#dfn-did-subjects" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-subjects-6">DID subject</a> or
    associated entities via one or more <a href="#dfn-service-endpoints" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-service-endpoints-1">service endpoints</a>.
    Examples include discovery services, agent services, social networking
    services, file storage services, and verifiable credential repository services.
  </dd>

  <dt><dfn data-lt="service endpoints|service endpoint" id="dfn-service-endpoints" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">service endpoint</dfn></dt>
  <dd>
    A network address, such as an HTTP URL, at which <a href="#dfn-service" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-service-1">services</a> operate on
    behalf of a <a href="#dfn-did-subjects" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-subjects-7">DID subject</a>.
  </dd>

  <dt><dfn data-lt="" id="dfn-service-endpoint-construction" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">service endpoint construction</dfn></dt>
  <dd>An algorithm that takes a <a href="#dfn-did-urls" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-urls-11">DID URL</a> and a service, and constructs
    a <a href="#dfn-service-endpoints" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-service-endpoints-2">service endpoint</a> URL See Section <a href="#service-endpoint-construction" class="sec-ref"><bdi class="secno">11. </bdi>Service Endpoint Construction</a>.</dd>

  <dt><dfn data-lt="" id="dfn-unverifiable-read" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">unverifiable read</dfn></dt>
  <dd> A low confidence implementation of a <a href="#dfn-did-method-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-method-s-7">DID method's</a> "Read" operation between the
    <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-11">DID resolver</a> and the <a href="#dfn-verifiable-data-registry" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-verifiable-data-registry-2">verifiable data registry</a>, to obtain the <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-20">DID document</a>.
    There is no guarantee about the integrity and correctness of the result. See Section <a href="#method-architectures" class="sec-ref"><bdi class="secno">6.1 </bdi>Method Architectures</a>.</dd>

  <dt>
    <dfn data-lt="verifiable data registry|verifiable data registries" id="dfn-verifiable-data-registry" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">
      verifiable data registry</dfn>
  </dt>
  <dd>
    A system that facilitates the creation, verification, updating, and/or
    deactivation of <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-17">decentralized identifiers</a> and <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-21">DID documents</a>. A
    verifiable data registry might also be used for other
    cryptographically-verifiable data structures such as <a data-link-type="dfn" href="https://www.w3.org/TR/vc-data-model/#dfn-verifiable-credential">verifiable
    credentials</a>. For more information, see the <abbr title="World Wide Web Consortium">W3C</abbr> Verifiable Credentials
    specification [<cite><a class="bibref" data-link-type="biblio" href="#bib-vc-data-model" title="Verifiable Credentials Data Model v1.1">VC-DATA-MODEL</a></cite>].
  </dd>

  <dt><dfn data-lt="" data-plurals="verification methods" id="dfn-verification-method" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">verification method</dfn></dt>
  <dd>
    <p>
      A set of parameters that can be used together with a process to independently
      verify a proof. For example, a cryptographic public key can be used as a
      verification method with respect to a digital signature; in such usage, it
      verifies that the signer possessed the associated cryptographic private key.
    </p>
    <p>
      "Verification" and "proof" in this definition are intended to apply broadly. For
      example, a cryptographic public key might be used during Diffie-Hellman key
      exchange to negotiate a shared symmetric key for encryption. This guarantees the
      integrity of the key agreement process. It is thus another type of verification
      method, even though descriptions of the process might not use the words
      "verification" or "proof."
    </p>
  </dd>

  <dt><dfn data-lt="" id="dfn-verifiable-read" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">verifiable read</dfn></dt>
  <dd> A high confidence implementation of a <a href="#dfn-did-method-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-method-s-8">DID method's</a> "Read" operation between the
    <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-12">DID resolver</a> and the <a href="#dfn-verifiable-data-registry" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-verifiable-data-registry-3">verifiable data registry</a>, to obtain the <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-22">DID document</a>.
    There are guarantees about the integrity and correctness of the result to the extent possible under the applicable <a href="#dfn-did-method-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-method-s-9">DID method</a>.
    See Section <a href="#method-architectures" class="sec-ref"><bdi class="secno">6.1 </bdi>Method Architectures</a>.</dd>

</dl>
</div>

</section>

<section id="resolving"><div class="header-wrapper"><h2 id="x3-did-resolution"><bdi class="secno">3. </bdi>DID Resolution</h2><a class="self-link" href="#resolving" aria-label="Permalink for Section 3."></a></div>


	<p>
		The <a href="#dfn-did-resolution" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolution-8">DID resolution</a> functions resolve a <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-18">DID</a> into a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-23">DID
		document</a> by using the "Read" operation of the applicable <a href="#dfn-did-method-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-method-s-10">DID method</a>
		as described in <a href="https://w3c.github.io/did-core/#method-operations">Method Operations</a>. All
		conforming <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-13">DID resolvers</a> implement the functions below, which have the
		following abstract forms:
	</p>

	<pre title="Abstract functions for DID Resolution" aria-busy="false"><code class="hljs">resolve(did, resolutionOptions) →
   « didResolutionMetadata, didDocument, didDocumentMetadata »

resolveRepresentation(did, resolutionOptions) →
   « didResolutionMetadata, didDocumentStream, didDocumentMetadata »</code></pre>

	<p>
		The <code>resolve</code> function returns the <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-24">DID document</a> in its
		abstract form (a <a href="https://infra.spec.whatwg.org/#maps">map</a>). The
		<code>resolveRepresentation</code> function returns a byte stream of the <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-25">DID
		Document</a> formatted in the corresponding representation.
	</p>

	<figure id="resolve-resolverepresentation">
		<img style="margin: auto; display: block;" src="diagrams/diagram-resolve-resolverepresentation.svg" alt="
Diagram illustrating how resolve() returns the DID document data model in
its abstract form and resolveRepresenation() returns it in one of the
conformant representations; conversion is possible using production and
consumption rules.">
		<figcaption><a class="self-link" href="#resolve-resolverepresentation">Figure <bdi class="figno">1</bdi></a> <span class="fig-title">
			Functions resolve() and resolveRepresentation().
			See also: <a class="longdesc-link" href="#resolve-resolverepresentation-longdesc">narrative description</a>.
		</span></figcaption>
	</figure>

	<div class="longdesc" id="resolve-resolverepresentation-longdesc">
		<p>
			The upper middle part of the diagram contains a rectangle with dashed grey outline, containing two
			blue-outlined rectangles, one above the other.
			The upper, larger rectangle is labeled, in blue, "Core Properties", and contains the following
			<a href="https://infra.spec.whatwg.org/#maps">INFRA</a> notation:
		</p>
		<pre aria-busy="false"><code class="hljs javascript">«[
  <span class="hljs-string">"id"</span> → <span class="hljs-string">"example:123"</span>,
  <span class="hljs-string">"verificationMethod"</span> → « «[
    <span class="hljs-string">"id"</span>: <span class="hljs-string">"did:example:123#keys-1"</span>,
    <span class="hljs-string">"controller"</span>: <span class="hljs-string">"did:example:123"</span>,
    <span class="hljs-string">"type"</span>: <span class="hljs-string">"Ed25519VerificationKey2018"</span>,
    <span class="hljs-string">"publicKeyBase58"</span>: <span class="hljs-string">"H3C2AVvLMv6gmMNam3uVA"</span>
  ]» »,
  <span class="hljs-string">"authentication"</span> → «
    <span class="hljs-string">"did:example:123#keys-1"</span>
  »
]»</code></pre>
		<p>
			The lower, smaller rectangle is labeled, in blue, "Core Representation-specific Entries (JSON-LD)", and
			contains the following monospaced <a href="https://infra.spec.whatwg.org/#maps">INFRA</a> notation:
		</p>
		<pre aria-busy="false"><code class="hljs css">«<span class="hljs-selector-attr">[ <span class="hljs-string">"@context"</span> → <span class="hljs-string">"https://www.w3.org/ns/did/v1"</span> ]</span>»</code></pre>
		<p>
			From the grey-outlined rectangle, three pairs of arrows extend to three
			different black-outlined rectangles, aligned in a horizontal row side-by-side, in the bottom half
			of the diagram. Each pair of arrows consists of
			one blue arrow pointing from the grey-outlined rectangle to the respective
			black-outlined rectangle, labeled "produce", and one red arrow pointing in the
			reverse direction, labeled "consume". The first black-outlined rectangle in the row
			is labeled "application/did+ld+json", and contains
			the following JSON-LD data:
		</p>
		<pre aria-busy="false"><code class="hljs json"><span class="hljs-punctuation">{</span>
  <span class="hljs-attr">"@context"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">[</span><span class="hljs-string">"https://www.w3.org/ns/did/v1"</span><span class="hljs-punctuation">]</span><span class="hljs-punctuation">,</span>
  <span class="hljs-attr">"id"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"did:example:123"</span><span class="hljs-punctuation">,</span>
  <span class="hljs-attr">"verificationMethod"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">[</span><span class="hljs-punctuation">{</span>
    <span class="hljs-attr">"id"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"did:example:123#keys-1"</span><span class="hljs-punctuation">,</span>
    <span class="hljs-attr">"controller"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"did:example:123"</span><span class="hljs-punctuation">,</span>
    <span class="hljs-attr">"type"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"Ed25519VerificationKey2018"</span><span class="hljs-punctuation">,</span>
    <span class="hljs-attr">"publicKeyBase58"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"H3C2AVvLMv6gmMNam3uVA"</span>
  <span class="hljs-punctuation">}</span><span class="hljs-punctuation">]</span><span class="hljs-punctuation">,</span>
  <span class="hljs-attr">"authentication"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">[</span>
    <span class="hljs-string">"did:example:123#keys-1"</span>
  <span class="hljs-punctuation">]</span>
<span class="hljs-punctuation">}</span></code></pre>
		<p>
			The second rectangle in the row is labeled "application/did+json" and contains the following
			JSON data:
		</p>
		<pre aria-busy="false"><code class="hljs json"><span class="hljs-punctuation">{</span>
  <span class="hljs-attr">"id"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"did:example:123"</span><span class="hljs-punctuation">,</span>
  <span class="hljs-attr">"verificationMethod"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">[</span><span class="hljs-punctuation">{</span>
    <span class="hljs-attr">"id"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"did:example:123#keys-1"</span><span class="hljs-punctuation">,</span>
    <span class="hljs-attr">"controller"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"did:example:123"</span><span class="hljs-punctuation">,</span>
    <span class="hljs-attr">"type"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"Ed25519VerificationKey2018"</span><span class="hljs-punctuation">,</span>
    <span class="hljs-attr">"publicKeyBase58"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"H3C2AVvLMv6gmMNam3uVA"</span>
  <span class="hljs-punctuation">}</span><span class="hljs-punctuation">]</span><span class="hljs-punctuation">,</span>
  <span class="hljs-attr">"authentication"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">[</span>
    <span class="hljs-string">"did:example:123#keys-1"</span>
  <span class="hljs-punctuation">]</span>
<span class="hljs-punctuation">}</span></code></pre>
		<p>
			The third rectangle in the row is labeled "application/did+cbor", and contains hexadecimal data.
		</p>
		<p>
			In the left part of the diagram, in the middle, there is a box, with black outline and light gray
			background. This box is labeled "VERIFIABLE DATA REGISTRY" and contains a symbol representing a graph
			with nodes and arcs. From this box, one arrow, labeled "resolve()", extends upwards and points to the
			top half of the diagram where the grey-outlined rectangle is located. Another arrow, labeled
			"resolveRepresentation()", extends downwards and points to the bottom half of the diagram, where the
			row of three black-outlined rectangles is located.
		</p>
	</div>

	<p>
		All conformant <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-14">DID resolvers</a> <em class="rfc2119">MUST</em> implement the <a href="#dfn-did-resolution" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolution-9">DID resolution</a>
		functions for at least one <a href="#dfn-did-method-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-method-s-11">DID method</a> and <em class="rfc2119">MUST</em> be able to return a
		<a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-26">DID document</a> in at least one conformant <a href="#dfn-representations" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-representations-2">representation</a>.
	</p>

	<p>
		Conforming <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-15">DID resolver</a> implementations do not alter the signature of
		these functions in any way. <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-16">DID resolver</a> implementations might map the
		<code>resolve</code> and <code>resolveRepresentation</code> functions to a
		method-specific internal function to perform the actual <a href="#dfn-did-resolution" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolution-10">DID resolution</a>
		process. <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-17">DID resolver</a> implementations might implement and expose
		additional functions with different signatures in addition to the
		<code>resolve</code> and <code>resolveRepresentation</code> functions specified
		here.
	</p>

	<p>
		The input variables
		of the <code>resolve</code> and <code>resolveRepresentation</code> functions are
		as follows:
	</p>

	<dl>
		<dt>
			did
		</dt>
		<dd>
			This is the <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-19">DID</a> to resolve. This input is <em class="rfc2119">REQUIRED</em> and the value <em class="rfc2119">MUST</em>
			be a conformant <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-20">DID</a> as defined in <a href="https://w3c.github.io/did-core/#did-syntax"></a>.
		</dd>
		<dt>
			resolutionOptions
		</dt>
		<dd>
			A <a href="#metadata-structure">metadata structure</a> containing properties
			defined in <a href="#did-resolution-options" class="sec-ref"><bdi class="secno">3.1 </bdi>DID Resolution Options</a>. This input is
			<em class="rfc2119">REQUIRED</em>, but the structure <em class="rfc2119">MAY</em> be empty.
		</dd>
	</dl>

	<p>
		These functions each return multiple values, and no limitations
		are placed on how these values are returned together.
		The return values of <code>resolve</code> are
		<a href="#dfn-didresolutionmetadata" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-didresolutionmetadata-1">didResolutionMetadata</a>, <a href="#dfn-diddocument" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-diddocument-1">didDocument</a>, and
		<a href="#dfn-diddocumentmetadata" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-diddocumentmetadata-1">didDocumentMetadata</a>. The return values of
		<code>resolveRepresentation</code> are
		<a href="#dfn-didresolutionmetadata" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-didresolutionmetadata-2">didResolutionMetadata</a>, <a href="#dfn-diddocumentstream" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-diddocumentstream-1">didDocumentStream</a>, and
		<a href="#dfn-diddocumentmetadata" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-diddocumentmetadata-2">didDocumentMetadata</a>. These values are described below:
	</p>

	<dl>
		<dt>
			<dfn id="dfn-didresolutionmetadata" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">didResolutionMetadata</dfn>
		</dt>
		<dd>
			A <a href="#metadata-structure">metadata structure</a> consisting of values
			relating to the results of the <a href="#dfn-did-resolution" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolution-11">DID resolution</a> process which typically
			changes between invocations of the <code>resolve</code> and
			<code>resolveRepresentation</code> functions, as it represents data about the
			resolution process itself. This structure is <em class="rfc2119">REQUIRED</em>, and in the case of an
			error in the resolution process, this <em class="rfc2119">MUST NOT</em> be empty. This metadata is
			defined by <a href="#did-resolution-metadata" class="sec-ref"><bdi class="secno">3.2 </bdi>DID Resolution Metadata</a>. If
			<code>resolveRepresentation</code> was called, this structure <em class="rfc2119">MUST</em> contain a
			<code>contentType</code> property containing the Media Type of the
			representation found in the <code>didDocumentStream</code>. If the resolution is
			not successful, this structure <em class="rfc2119">MUST</em> contain an <code>error</code> property
			describing the error.
		</dd>
		<dt>
			<dfn id="dfn-diddocument" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">didDocument</dfn>
		</dt>
		<dd>
			If the resolution is successful, and if the <code>resolve</code> function was
			called, this <em class="rfc2119">MUST</em> be a <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-27">DID document</a> abstract data model (a <a href="https://infra.spec.whatwg.org/#maps">map</a>) as described in <a href="https://w3c.github.io/did-core/#data-model"></a> that
			is capable of being transformed into a <a href="https://w3c.github.io/did-core/#dfn-did-documents">conforming DID Document</a>
			(representation), using the production rules specified by the representation.
			The value of <code><a href="https://w3c.github.io/did-core/#dfn-id">id</a></code> in the resolved <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-28">DID document</a> <em class="rfc2119">MUST</em>
			match the <a href="#dfn-decentralized-identifiers" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-decentralized-identifiers-21">DID</a> that was resolved. If the resolution is unsuccessful, this
			value <em class="rfc2119">MUST</em> be empty.
		</dd>
		<dt>
			<dfn id="dfn-diddocumentstream" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">didDocumentStream</dfn>
		</dt>
		<dd>
			If the resolution is successful, and if the <code>resolveRepresentation</code>
			function was called, this <em class="rfc2119">MUST</em> be a byte stream of the resolved <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-29">DID
			document</a> in one of the conformant
			<a href="https://w3c.github.io/did-core/#representations">representations</a>. The byte stream might then be
			parsed by the caller of the <code>resolveRepresentation</code> function into a
			<a href="https://w3c.github.io/did-core/#data-model">data model</a>, which can in turn be validated and
			processed. If the resolution is unsuccessful, this value <em class="rfc2119">MUST</em> be an empty
			stream.
		</dd>
		<dt>
			<dfn id="dfn-diddocumentmetadata" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">didDocumentMetadata</dfn>
		</dt>
		<dd>
			If the resolution is successful, this <em class="rfc2119">MUST</em> be a <a href="#metadata-structure">metadata structure</a>. This structure contains
			metadata about the <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-30">DID document</a> contained in the <code>didDocument</code>
			property. This metadata typically does not change between invocations of the
			<code>resolve</code> and <code>resolveRepresentation</code> functions unless the
			<a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-31">DID document</a> changes, as it represents metadata about the <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-32">DID
			document</a>. If the resolution is unsuccessful, this output <em class="rfc2119">MUST</em> be an empty <a href="#metadata-structure">metadata structure</a>. Properties defined by this
			specification are in <a href="#did-document-metadata" class="sec-ref"><bdi class="secno">3.3 </bdi>DID Document Metadata</a>.
		</dd>
	</dl>

	<section id="did-resolution-options"><div class="header-wrapper"><h3 id="x3-1-did-resolution-options"><bdi class="secno">3.1 </bdi>DID Resolution Options</h3><a class="self-link" href="#did-resolution-options" aria-label="Permalink for Section 3.1"></a></div>


		<p>
			The possible properties within this structure and their possible values are
			registered in the DID Specification Registries [<cite><a class="bibref" data-link-type="biblio" href="#bib-did-spec-registries" title="Decentralized Identifier Extensions">DID-SPEC-REGISTRIES</a></cite>]. This
			specification defines the following common properties.
		</p>

		<dl>
			<dt>
				accept
			</dt>
			<dd>
				The Media Type of the caller's preferred <a href="#dfn-representations" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-representations-3">representation</a> of the <a href="#dfn-did-documents" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-documents-33">DID
				document</a>. The Media Type <em class="rfc2119">MUST</em> be expressed as an <a data-lt="ascii
string" data-link-type="dfn" href="https://infra.spec.whatwg.org/#ascii-string">ASCII string</a>. The <a href="#dfn-did-resolver-s" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-did-resolver-s-18">DID resolver</a> implementation <em class="rfc2119">SHOULD</em> use this
				value to determine the <a href="#dfn-representations" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-representations-4">representation</a> contained in the returned
				<code>didDocumentStream</code> if such a <a href="#dfn-representations" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-representations-5">representation</a> is supported and
				available. This property is <em class="rfc2119">OPTIONAL</em> for the <code>resolveRepresentation</code>