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<!DOCTYPE html>
<html>
<head>
<title>Verifiable Claims Data Model 1.0</title>
<meta http-equiv='Content-Type' content='text/html;charset=utf-8'/>
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subtitle: "Expressing verifiable information on the Web",
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<body>
<section id='abstract'>
<p>
Driver's licenses are used to claim that we are capable of operating a motor
vehicle, university degrees can be used to claim our education status, and
government-issued passports enable holders to travel between countries.
This specification provides a standard way to express these sorts of claims
on the Web in a way that is cryptographically secure, privacy respecting,
and automatically verifiable.
</p>
</section>
<section id='sotd'>
<p>
Comments regarding this document are welcome. Please file issues
directly on <a href="https://github.com/w3c/vc-data-model/issues/">GitHub</a>,
or send them to
<a href="mailto:public-vc-comments@w3.org">public-vc-comments@w3.org</a>
(<a href="mailto:public-vc-comments-request@w3.org?subject=subscribe">subscribe</a>,
<a href="https://lists.w3.org/Archives/Public/public-vc-comments/">archives</a>).
</p>
</section>
<section>
<h2>Introduction</h2>
<p>
Granting a benefit requires proof and verification. Some benefits demand
a formal process that includes three parties. In this process,
the <strong>holder</strong> asks for the benefit and the <strong>inspector-verifier
</strong> grants or denies the benefit based on verification of the holder’s
qualification from a trusted <strong>issuer</strong>.
</p>
<p>
For example, we use a
driver's licenses to prove that we are capable of operating a motor vehicle,
a university degree to prove our education status, and government-issued
passports to grant travel between countries. This specification provides a
standard way to express these claims on the Web in a way that is
cryptographically secure, privacy respecting, and automatically verifiable.
</p>
<p>
For those that are unfamiliar with the concepts related to verifiable claims,
the following sections provide an overview of:
</p>
<ol>
<li>
what a verifiable claim contains,
</li>
<li>
an ecosystem where verifiable claims are expected to be useful, and
</li>
<li>
the use cases and requirements that informed this specification
</li>
</ol>
</p>
<section>
<h3>What is a Verifiable Claim?</h3>
<p class="issue">
Expand on introductory verifiable claims section that doesn't dive too deeply
into the details but rather provides an overview of what we're trying to
achieve.
</p>
</section>
<section>
<h3>Ecosystem Overview</h3>
<p>
This section outlines a basic set of roles and an ecosystem where verifiable
claims are expected to be useful. In this section, we distinguish the essential
roles of core actors and the relationships between them; how do they interact?
A role is an abstraction that might be implemented in many different ways. The
separation of roles suggests likely interfaces and/or protocols for
standardization. The following roles are introduced in this specification:
</p>
<p class="issue" data-title="Incomplete list of roles and terminology">
The VCWG is actively discussing the number of roles and terminology used
in this specification.
The group expects terminology and role identification to be an ongoing
discussion and will be influenced by
public feedback on the specification. At present, the following incomplete
list of roles and terminology have been considered: Subject, Issuer, Authority,
Author, Signatory, Holder, Presenter, Asserter, Claimant, Sharer,
Subject's Agent, Prover, Mediator, Inspector, Evaluator, Verifier, Consumer, and
Relying Party. Some of these are aliases for the same concept, others are
possibly new roles in the ecosystem. Reviewers should be aware that the
terminology used in this document is not necessarily final and the group is
actively soliciting feedback on the roles and terminology used in this
specification.
</p>
<dl>
<dt><a>holder</a></strong></dt>
<dd>
An <a>entity</a> that is in control of one or more <a>verifiable claims</a>.
Examples of holders include students, employees, and customers.
</dd>
<dt><a>issuer</a></dt>
<dd>
An <a>entity</a> that creates a <a>verifiable claim</a>, associates it
with a particular <a>subject</a>, and transmits it to a <a>holder</a>.
Examples of issuers include corporations, governments, and individuals.
</dd>
<dt><a>inspector-verifier</a></dt>
<dd>
An <a>entity</a> that receives one or more <a>verifiable claims</a> for
processing. Examples of inspector-verifiers include employers, security personnel, and
websites.
</dd>
<dt><a>identifier registry</a></dt>
<dd>
Mediates the creation and verification of <a>subject</a> identifiers.
Examples of identifier registries include corporate employee databases,
government ID databases, and distributed ledgers.
</dd>
</dl>
<figure>
<img style="margin: auto; display: block;" width="75%" src="diagrams/ecosystem.svg">
<figcaption style="text-align: center;">
The roles and information flows that form the basis for this specification.
</figcaption>
</figure>
<p class="note">
The ecosystem above is provided as an example to the reader in order to ground
the rest of the concepts in this specification. Other ecosystems exist, such as
protected environments or proprietary systems, where verifiable claims also
provide benefit.
</p>
</section>
<section>
<h3>Use Cases and Requirements</h3>
<p>
The Verifiable Claims Use Cases[[VC-USECASES]] document outlines a number of
key topics that readers may find useful, including:
</p>
<ul>
<li>
a more thorough explanation of the
<a href="https://www.w3.org/TR/verifiable-claims-use-cases/#user-roles">roles</a>
introduced above,
</li>
<li>
the
<a href="https://www.w3.org/TR/verifiable-claims-use-cases/#user-needs">needs</a>
identified in market verticals like education, finance, healthcare, retail,
professional licensing, and government,
</li>
<li>
common
<a href="https://www.w3.org/TR/verifiable-claims-use-cases/#user-tasks">tasks and requirement</a>
performed by the roles in the ecosystem, and
</li>
<li>
common
<a href="https://www.w3.org/TR/verifiable-claims-use-cases/#user-sequences">sequences and flows</a>
identified by the Working Group.
</li>
</ul>
<p>
As a result of documenting and analyzing the use cases document, a number of
desirable capabilities have been identified as requirements for this
specification, specifically:
</p>
<ul>
<li>
<a>Holders</a> MUST receive and store <a>verifiable claims</a> from
<a>issuers</a> through an agent that the issuer does not need to trust.
</li>
<li>
<a>Holders</a> SHOULD be positioned between <a>issuers</a> and <a>inspector-verifiers</a>
and mediate the transmission of <a>verifiable claims</a>.
</li>
<li>
<a>Holders</a> MUST provide <a>verifiable claims</a> to <a>inspector-verifiers</a>
through an agent that inspector-verifiers needn't trust; they only need to trust
<a>issuers</a>.
</li>
<li>
<a>Verifiable claims</a> MUST be associated with <a>subjects</a>, not
particular services; <a>holders</a> SHOULD decide how to aggregate and manage
<a>verifiable claims</a>.
</li>
<li>
<a>Holders</a> SHOULD be able to easily control and own their own identifiers.
</li>
<li>
<a>Holders</a> MUST control which <a>verifiable claims</a> to use and when.
</li>
<li>
<a>Holders</a> MUST be able to freely choose and change the agents they employ
to help them manage and share their <a>verifiable claims</a>.
</li>
<li>
<a>Holders</a> that share <a>verifiable claims</a> MUST NOT be required to
reveal the identity of the <a>inspector-verifier</a> to <a>issuers</a>.
</li>
<li>
A <a>verifiable claim</a> MUST be expressed in one or more standard,
machine-readable data formats for expressing <a>verifiable claims</a> which
can also be extended with minimal coordination.
</li>
<li>
<a>Verifiable claims</a> MUST be able to be indepenently issued, stored, and
verified.
</li>
<li>
<a>Verifiable Claims</a> MUST be able to be revoked by the <a>issuer</a>.
</li>
</ul>
<p class="issue">
There are
<a href="https://www.w3.org/TR/verifiable-claims-use-cases/#user-tasks">other requirements</a>
listed in the Verifiable Claims Use Cases
document that may or may not be aligned with the requirements listed above.
The VCWG will be ensuring alignment of the list of requirements from both
documents over time and will most likely move the list of requirements to a
single document.
</p>
</section>
</section>
<section>
<h2>Terminology</h2>
<div data-include="./terms.html"
data-oninclude="restrictReferences">
</div>
<p class="issue" data-number="55" data-title="Multiple subjects in a credential">
It is currently possible to include multiple subjects in a credential. The
terminology above glosses over that fact. The group is debating if the
terminology should be modified to include this nuance, or if the nuance would
make grasping the basic concepts more difficult.
</p>
</section>
<section>
<h2>Core Data Model</h2>
<p>
The following sections outline core data model concepts, such as
<a>claims</a>, <a>credentials</a>, and <a>profiles</a>, that form the
foundation of this specification.
</p>
<section>
<h3>Claims</h3>
<p>
A <a>claim</a> is statement about a <a>subject</a>.
A <a>subject</a> is an <a>entity</a> about which <a>claims</a> may be made.
<a>Claims</a> are expressed using
<strong><em>subject</em></strong>-<dfn data-lt="property|properties">property</dfn>-<dfn>value</dfn>
relationships.
</p>
<figure>
<img style="margin: auto; display: block;"
width="50%" src="diagrams/claim.svg">
<figcaption style="text-align: center;">
The basic structure of a claim.
</figcaption>
</figure>
<p>
The data model for <a>claims</a> described above is powerful and can be used to
express a large variety of statements. For example, whether or not someone is
over the age of 21 may be expressed as follows:
</p>
<figure>
<img style="margin: auto; display: block;"
width="50%" src="diagrams/claim-example.svg">
<figcaption style="text-align: center;">
An example of a basic claim that expresses that Pat is over the age of 21.
</figcaption>
</figure>
<p>
These claims may be merged together to express a graph of
information about a particular subject. The example below extends the
data model above by adding claims that state that Pat knows Sam and that
Sam is a student.
</p>
<figure>
<img style="margin: auto; display: block;"
width="75%" src="diagrams/claim-extended.svg">
<figcaption style="text-align: center;">
Multiple claims may be combined to express a more complex graph.
</figcaption>
</figure>
<p>
At this point, the concept of a <a>claim</a> has been introduced. To make the
claim verifiable, more information must be added to the graph of information.
</p>
</section>
<section>
<h2>Credentials</h2>
<p>
A <a>credential</a> is set of one or more <a>claims</a> about a <a>subject</a>.
It typically includes an identifier to uniquely identify the
credential. Credential metadata may also be included to express concepts
such as when the credential expires. A digital signature is almost always
appended by the <a>issuer</a> of the credential to enable verifiability of
the credential. Therefore, a <strong>verifiable credential</strong> is a set
of claims that are tamper-resistant and whose authorship can be
cryptographically verified.
</p>
<figure>
<img style="margin: auto; display: block;" width="50%" src="diagrams/credential.svg">
<figcaption style="text-align: center;">
The basic components of a verifiable credential.
</figcaption>
</figure>
<p>
Examples of verifiable credentials include digital employee identification
cards, digital proofs of age, and digital educational certificates.
</p>
</section>
<section>
<h2>Profiles</h2>
<p>
As this specification takes a privacy-first approach, it is important that
the entities that use this technology are able to express only the portions of
their persona that are appropriate for the situation. The expression of a
subset of one's persona is called a <a>verifiable profile</a>.
</p>
<p>
A <a>verifiable profile</a> is a collection of one or more
<a>verifiable credentials</a> typically about the same <a>subject</a> that
have been issued by multiple <a>issuers</a>. The aggregation of this
information typically expresses an aspect of a person, organization, or entity.
</p>
<figure>
<img style="margin: auto; display: block;"
width="50%" src="diagrams/profile.svg">
<figcaption style="text-align: center;">
The basic components of a verifiable profile.
</figcaption>
</figure>
<p>
Examples of different profiles include a person's professional persona, online
gaming persona, or home life persona.
</p>
<!--
<p>This section describes a data model for <a>verifiable
profiles</a> and <a>verifiable credentials</a>, the latter covering
both claims and verifiable claims, that is compatible with the
requirements and use cases expected to be addressed by this
group.</p>
<section>
<h2>General Characteristics</h2>
<p>Both the <a>Verifiable Profile Model</a> and <a>Entity
Credential Model</a> consist of a collection of name-value
pairs which will be referred to as
<dfn data-lt="property">properties</dfn> in this document.
The following subsections describe the required and optional
properties for both. The link between the two is in
the <var>id</var> property. The <a>Verifiable Profile Model</a>
defines a <a>subject</a> identifier in
the <a href="#entity-id"><var>id</var></a> property, while
the claims section of the <a>Verifiable Credential Model</a> uses
the <a href="#claim-id"><var>id</var></a> property to refer to
that <a>subject</a> identifier.</p>
<p>This document purposely defines the data model without
using a concrete syntax such as WebIDL, JSON, or JSON-LD to
avoid implying a bias towards any particular one syntax.
Section <a href="#syntaxes"></a>
defines how the data model is to be expressed in those
representation languages.</p>
</section>
<section>
<h2><dfn>Verifiable Profile Model</dfn></h2>
<p>Unlike the <a>properties</a> in
the <a href="#ec-claim"><var>claim</var></a> section of
the <a>Verifiable Credential Model</a>, the <a>properties</a> in
the Verifiable Profile Model are merely information that,
together with a <a>subject</a>
identifier <a href="#entity-id"><var>id</var></a>,
constitute an verifiable profile. The properties are not claims
and are not intended to be verifiable.</p>
<p>The following properties are required in the Entity
Profile Model:</p>
<dl>
<dt><span id="entity-id"><var>id</var></span></dt>
<dd>This is a URI representing the <a>subject</a>. This
identifier MAY be long-lived but does not have to be.</dd>
<dt><var>type</var></dt>
<dd>This is an unordered set of URIs representing the types
or classes of which this data set is a member. As an
<a>verifiable profile</a>, at a minimum the class "Entity"
must be a member of the set. Additional
application-specific values are permitted in the set.</dd>
</dl>
<p>The following properties are optional in the Entity
Profile Model:</p>
<dl>
<dt><var>signature</var></dt>
<dd>The method used for a signature will vary by
representation language. However, if present this property
is expected to have a value that is a set of name-value
pairs including at least a signature, a reference to the
signing entity, and a representation of the signing
date.</dd>
</dl>
<p>Additionally, any property name not listed above is
permitted as an optional custom <a>property</a>.</p>
</section>
<section>
<h2><dfn>Verifiable Credential Model</dfn></h2>
<p>Unlike the <a>properties</a> in the <a>Verifiable Profile
Model</a>, the <a>properties</a> in
the <a href="#ec-claim"><var>claim</var></a> section of the
Verifiable Credential Model are claims made by an <a>entity</a>
about the <a>subject</a> defined in an <a>verifiable
profile</a>. The Verifiable Credential Model includes both
issuance-related properties and the
aforementioned <a href="#ec-claim"><var>claim</var></a>
property that further contains the properties of the claim
itself.</p>
<p>The following properties are required in the Entity
Credential Model:</p>
<dl>
<dt><var>id</var></dt>
<dd>URI representing this specific <a>verifiable credential</a></dd>
<dt><var>type</var></dt>
<dd>This is an unordered set of URIs representing the types
or classes of which this data set is a member. As an
<a>verifiable credential</a>, at a minimum the class
"Credential" must be a member of the set. Additional
application-specific values are permitted in the
set.</dd>
<dt><span id="ec-claim"><var>claim</var></span></dt>
<dd>This is the actual claim. Its value is a set of
<a>properties</a> as follows:
<p>The following properties are required in
a <var>claim</var> value:</p>
<dl>
<dt><span id="claim-id"><var>id</var></span></dt>
<dd>The <a>subject</a> of the claim, the property value
is expected to be a valid
<a href="#entity-id">Verifiable Profile <var>id</var></a>.</dd>
<dt>At least one custom <a>property</a></dt>
<dd>N/A</dd>
</dl>
<p>Additionally, any property name not listed above is
permitted as an optional custom <a>property</a>.</p>
</dd>
</dl>
<p>The following <a>properties</a> are optional in the Entity
Credential Model:</p>
<dl>
<dt><var>issuer</var></dt>
<dd>This is a URI for the issuer of the claim.</dd>
<dt><var>issued</var></dt>
<dd>This is the date, in string format, when the claim was
issued.</dd>
</dl>
<p>Additionally, any property name not listed above is
permitted as an optional custom <a>property</a>.</p>
</section>
<section>
<h2>Verifiable Claims Model</h2>
<p>The claims in the <a>Verifiable Credential Model</a> can be
made verifiable by adding the following <a>property</a> to
the <a>Verifiable Credential Model</a>:</p>
<dl>
<dt><var>signature</var></dt>
<dd>The method used for a signature will vary by
representation language. However, this property is expected
to have a value that is a set of name-value pairs including
at least a signature, a reference to the signing entity, and
a representation of the signing date.</dd>
</dl>
</section>
!-->
</section>
</section>
<section>
<h1>Basic Concepts</h1>
<section>
<h2>Issuer</h2>
<p>
Issuer information may be expressed via the following <a>properties</a>:
</p>
<dl>
<dt><var>issuer</var></dt>
<dd>
The value of this property MUST be a URI. It is RECOMMENDED that dereferencing
the URI results in a document containing machine-readable information about
the issuer that may be used to verify the information expressed in the
<a>credential</a>.
</dd>
<dt><var>issued</var></dt>
<dd>
The value of this property MUST be a string value of an [[!ISO8601]] combined
date and time string and represents the date and time the <a>credential</a>
was issued. Note that this date represents the earliest date when the
information associated with the <var>claim</var> property became valid.
</dd>
</dl>
<pre class="example nohighlight" title="Usage of issuer properties">
{
"id": "http://dmv.example.gov/credentials/3732",
"type": ["Credential", "ProofOfAgeCredential"],
<span class="highlight">"issuer": "https://dmv.example.gov/issuers/14"</span>,
<span class="highlight">"issued": "2010-01-01T19:73:24Z"</span>,
"claim": {
"id": "did:example:ebfeb1f712ebc6f1c276e12ec21",
"ageOver": 21
},
"signature": { ... }
}
</pre>
</section>
<section>
<h2>Signature</h2>
<p>
A <a>credential</a> MAY be made verifiable by adding the following
<a>property</a>:
</p>
<dl>
<dt><var>signature</var></dt>
<dd>
The method used for a signature will vary byrepresentation language. However,
this property is expected to have a value that is a set of name-value pairs
including at least a signature, a reference to the signing entity, and
a representation of the signing date.</dd>
</dl>
<pre class="example nohighlight" title="Usage of signature property">
{
"id": "http://example.gov/credentials/3732",
"type": ["Credential", "ProofOfAgeCredential"],
"issuer": "https://dmv.example.gov",
"issued": "2010-01-01",
"claim": {
"id": "did:example:ebfeb1f712ebc6f1c276e12ec21",
"ageOver": 21
},
<span class="highlight">"signature": {
"type": "LinkedDataSignature2017",
"created": "2017-06-18T21:19:10Z",
"creator": "https://example.com/jdoe/keys/1",
"nonce": "c0ae1c8e-c7e7-469f-b252-86e6a0e7387e",
"signatureValue": "BavEll0/I1zpYw8XNi1bgVg/sCneO4Jugez8RwDg/+
MCRVpjOboDoe4SxxKjkCOvKiCHGDvc4krqi6Z1n0UfqzxGfmatCuFibcC1wps
PRdW+gGsutPTLzvueMWmFhwYmfIFpbBu95t501+rSLHIEuujM/+PXr9Cky6Ed
+W3JT24="
}</span>
}
</pre>
</section>
<section>
<h2>Expiration</h2>
<p>
Expiration information for the <a>credential</a> MAY be provided by adding
the following <a>property</a>:
</p>
<dl>
<dt><var>expires</var></dt>
<dd>
The value of this property MUST be a string value of an [[!ISO8601]] combined
date and time string and represents the date and time the <a>credential</a>
will cease to be valid.
</dd>
</dl>
<pre class="example nohighlight" title="Usage of expires property">
{
"id": "http://dmv.example.gov/credentials/3732",
"type": ["Credential", "ProofOfAgeCredential"],
"issuer": "https://dmv.example.gov/issuers/14",
"issued": "2010-01-01T19:73:24Z",
<span class="highlight">"expires": "2020-01-01T19:73:24Z"</span>,
"claim": {
"id": "did:example:ebfeb1f712ebc6f1c276e12ec21",
"ageOver": 21
},
"signature": { ... }
}
</pre>
</section>
<section>
<h2>Revocation</h2>
<p>Revocation information for the claims in the
Verifiable Claims Model may be provided by adding the
following <a>property</a>:
</p>
<dl>
<dt><var>revocation</var></dt>
<dd>The value of this property MUST be a revocation scheme that
provides enough information to determine whether or not the
credential has been revoked. The revocation scheme will vary
depending on a variety of factors, such as whether it is
simple to implement or privacy-enhancing.
</dd>
</dl>
<p class="issue" data-number="35" data-title="Define ONE concrete format for the revocationList parameter ">
The group is currently determining whether or not they should publish a
very simple scheme for revocation as a part of this specification.
</p>
<pre class="example nohighlight" title="Usage of revocation property">
{
"id": "http://dmv.example.gov/credentials/3732",
"type": ["Credential", "ProofOfAgeCredential"],
"issuer": "https://dmv.example.gov/issuers/14",
"issued": "2010-01-01T19:73:24Z",
"claim": {
"id": "did:example:ebfeb1f712ebc6f1c276e12ec21",
"ageOver": 21
},
<span class="highlight">"revocation": {
"id": "https://dmv.example.gov/revocation/24,
"type": "RevocationList2017"
}</span>,
"signature": { ... }
}
</pre>
</section>
</section>
<section>
<h1>Advanced Concepts</h1>
<section>
<h2>Evidence</h2>
<p>Evidence information for the claims in the
Verifiable Claims Model may be provided by adding the
following <a>property</a>:
</p>
<dl>
<dt><var>evidence</var></dt>
<dd>The value of this property MUST be one or more evidence schemes
that provides enough information to a <a>inspector-verifier</a>
to determine whether or not the evidence gathered meets their
requirements.
</dd>
</dl>
<p class="issue" data-title="Define ONE concrete format for the evidence parameter ">
The group is currently determining whether or not they should publish a
very simple scheme for evidence as a part of this specification.
</p>
<pre class="example nohighlight" title="Usage of evidence property">
{
"id": "http://dmv.example.gov/credentials/3732",
"type": ["Credential", "ProofOfAgeCredential"],
"issuer": "https://dmv.example.gov/issuers/14",
"issued": "2010-01-01T19:73:24Z",
"claim": {
"id": "did:example:ebfeb1f712ebc6f1c276e12ec21",
"ageOver": 21
},
<span class="highlight">"evidence": {
"id": "https://dmv.example.gov/evidence/f2aeec97-fc0d-42bf-8ca7-0548192d4231",
"type": "DocumentVerification",
"verifier": "https://dmv.example.gov/issuers/14",
"evidenceDocument": "DriversLicense",
"subjectPresence": "Physical",
"documentPresence": "Physical"
}</span>,
"signature": { ... }
}
</pre>
</section>
</section>
<section>
<h1>Verification</h1>
<p>
This section describes a number of checks required to verify a claim.
Some checks are essential for all verifiable claims, while some are
applicable to only some claims.
</p>
<section>
<h3>Syntax</h3>
<ul>
<li>Document is syntactically valid (e.g. JSON, JSON-LD).</li>
</ul>
</section>
<section>
<h3>Credential</h3>
<ul>
<li>Required properties are present. For example, for a
Credential, <code>type</code> and <code>claim</code> are
required.</li>
<li>Property values match expectations described in the
specification. For example, the document type for a verifiable
claim must contain the class "Credential".</li>
</ul>
</section>
<section>
<h3>Issuer</h3>
<ul>
<li>The <code>issuer</code> id must match expectations. Likely,
that means it is the id of a known and trusted <a>verifiable
profile</a>.</li>
<li>Recent metadata about the <code>issuer</code> which was published
by the issuer MUST be available.</li>
</ul>
</section>
<section>
<h3>Subject</h3>
<ul>
<li>The claim subject identifier must match expectations.
Likely, that means it is the id of a known and trusted
<a>verifiable profile </a> for the subject of the claim. If the
entity that is subject of a claim has transmitted it to the
inspector-verifier, the subject may be able to prove ownership of key
identifying properties such as email address(es) and public
key(s).</li>
</ul>
</section>
<section>
<h3>Signature</h3>
<ul>
<li>The document signature is available in the form of a known
signature suite.</li>
<li>Required signature properties are present. For example, for a
Linked Data Signature, <code>type</code>, <code>created</code>,
<code>creator></code>, and <code>signatureValue</code> are present.
</li>
<li>The public key associated with the signature is available
and a trustworthy link between this signing key and the
issuer's <a>verifiable profile</a> may be established. The key must
not be revoked or expired.</li>
<li>The cryptographic signature is valid.</li>
</ul>
</section>
<section>
<h3>Expiration</h3>
<ul>
<li>The <code>issued</code> date must be in the expected range.
For example, an inspector-verifier may wish to ensure that the recorded
issued date of valid claims is not in the future.</li>
</ul>
</section>
<section>
<h3>Revocation</h3>
<ul>
<li>If revocation instructions are present, the claim must not
have been revoked.</li>
</ul>
</section>
<section>
<h3>Fitness for Purpose</h3>
<ul>
<li>The custom properties in the <a>claim</a> should be
appropriate for the inspector-verifier's purpose. For example if an
inspector-verifier needs to determine that a subject is older than 21
years of age, they may accept claims of specific birthdate or
abstract properties such as <code>ageOver</code>.</li>
<li>The issuer is trusted by the inspector-verifier to make the claims
at hand. For example, Fast Food Resturant A will not be trusted
to make a claim that an individual may enjoy a lifetime 10%
discount to its competitor Fast Food Restaurant B.</li>
<li>If the <a>issuer</a> has placed any policy information about
the use of the <a>credential</a>, e.g. intended
<a>inspector-verifiers</a>, expiration date, etc., that this
policy is adhered to.</li>
<li>If the <a>holder</a> has placed any policy information about
the use of the <a>credential</a>, e.g. intended
<a>inspector-verifiers</a>, restricted usage rights, etc., that this
policy is adhered to.</li>
</ul>
</section>
</section>
<section>
<h2>Syntaxes</h2>
<p>This section defines how the data model described in
Section <a href="data-model"></a> is realized in each of 3
different languages: JSON, JSON-LD, and WebIDL. Although
syntactic mappings are only provided for these three different
languages, applications and services may also use any other data
representation language (XML, for example) that can support the
data model.
</p>
<section>
<h2>JSON</h2>
<section>
<h2>Verifiable Credential</h2>
<p>In JSON, an instance of the Verifiable Credential
is expressed as a single JSON object whose
properties are the verifiable credential's
<a>properties</a>, with the following value type assignments:</p>
<ul>
<li>Any number value MUST be represented as a Number type.</li>
<li>Any boolean value MUST be represented as a Boolean type.</li>
<li>Any sequence value MUST be represented as an Array type.</li>
<li>Any unordered set of values MUST be represented as
an Array type.</li>
<li>Any set of <a>properties</a> MUST be represented as
an Object type.</li>
<li>Any empty value MUST be represented as a null value.</li>
<li>Any other value MUST be represented as a String type.</li>
</ul>
<p>The following example demonstrates how to express
an <a>verifiable credential</a> containing a simple
(unverifiable) <a>claim</a> about a particular
<a>subject</a>. In this case, the claim is that
the <a>subject</a> with
the <a href="#entity-id">Verifiable Profile <var>id</var></a>
of
<code>did:ebfeb1f712ebc6f1c276e12ec21</code> is 21 years
of age or older. While a human reading the
property <code>ageOver</code> may be able to guess its
meaning by its name, no machine-readable semantics for the
name are provided. There is information about the <a>claim</a>
itself, such as an identifier for the <a>entity</a> that issued
it and a date for when it was issued. </p>
<pre class="example nohighlight" title="A simple claim">{
<span class="subject">"id": "did:example:ebfeb1f712ebc6f1c276e12ec21"</span>, <span class="comment">// subject identifier</span>
<span class="property">"ageOver": 21</span> <span class="comment">// property-value pair</span>
}</pre>
<p>The following example demonstrates how to express the
same <a>claim</a> about the same <a>subject</a>, but in a
verifiable form. As such, it contains
a <code>signature</code> that can be used to verify its
entire contents, including the claim.</p>
<pre class="example" title="A simple verifiable credential">{
"id": "http://example.gov/credentials/3732",
"type": ["Credential", "ProofOfAgeCredential"],
"issuer": "https://dmv.example.gov",
"issued": "2010-01-01",
"claim": {
"id": "did:example:ebfeb1f712ebc6f1c276e12ec21",
"ageOver": 21
},
"revocation": {
"id": "http://example.gov/revocations/738",
"type": "SimpleRevocationList2017"
},
"signature": {
"type": "LinkedDataSignature2015",
"created": "2016-06-18T21:19:10Z",
"creator": "https://example.com/jdoe/keys/1",
"domain": "json-ld.org",
"nonce": "598c63d6",
"signatureValue": "BavEll0/I1zpYw8XNi1bgVg/sCneO4Jugez8RwDg/+
MCRVpjOboDoe4SxxKjkCOvKiCHGDvc4krqi6Z1n0UfqzxGfmatCuFibcC1wps
PRdW+gGsutPTLzvueMWmFhwYmfIFpbBu95t501+rSLHIEuujM/+PXr9Cky6Ed
+W3JT24="
}
}</pre>
<p>The following example demonstrates how one could
express the same <a>claim</a> about the