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<!DOCTYPE html>
<html lang="en">
<head>
<title>JSON-LD 1.1 Framing</title>
<meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
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{ name: "Pierre-Antoine Champin",
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// authors, add as many as you like.
// This is optional, uncomment if you have authors as well as editors.
// only "name" is required. Same format as editors.
authors: [
{ name: "Dave Longley",
url: "https://digitalbazaar.com/",
company: "Digital Bazaar",
companyURL: "https://digitalbazaar.com/",
note: "v1.0" },
{ name: "Manu Sporny",
url: "http://manu.sporny.org/",
company: "Digital Bazaar",
companyURL: "https://digitalbazaar.com/",
note: "v1.0" },
{ name: "Gregg Kellogg",
url: "https://greggkellogg.net/",
w3cid: "44770",
note: "v1.0 and v1.1" },
{ name: "Markus Lanthaler",
url: "https://www.markus-lanthaler.com/",
company: "Google",
companyURL: "https://www.google.com/",
note: "v1.0" },
{ name: "Niklas Lindström",
url: "http://neverspace.net/",
note: "v1.0" }
],
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<style>
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table, thead, tr, td { padding: 5px; border-width: 1px; border-spacing: 0px; border-style: solid; border-collapse: collapse; }
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</head>
<body>
<section id="abstract">
<p>JSON-LD Framing allows developers to query by example and
force a specific tree layout to a JSON-LD document.</p>
<p>This specification describes a superset of the features defined in
[[[JSON-LD10-FRAMING]]] [[JSON-LD10-FRAMING]]
and, except where noted,
the algorithms described in this specification are fully compatible
with documents created using the previous community standard.</p>
</section>
<section id='sotd'>
<p>This document has been developed by the
<a href="https://www.w3.org/2018/json-ld-wg/">JSON-LD Working Group</a> and was derived from the <a href="https://www.w3.org/community/json-ld/">JSON-LD Community Group's</a> <a href="https://www.w3.org/2018/jsonld-cg-reports/json-ld-framing/">Final Report</a>.</p>
<p>There is a
<a href="https://json-ld.org/playground/">live JSON-LD playground</a> that is capable
of demonstrating the features described in this document.</p>
<section>
<h2>Set of Documents</h2>
<p>This document is one of three JSON-LD 1.1 Recommendations produced by the
<a href="https://www.w3.org/2018/json-ld-wg/">JSON-LD Working Group</a>:</p>
<ul>
<li>[[[JSON-LD11]]]</li>
<li>[[[JSON-LD11-API]]]</li>
<li><a href="">JSON-LD 1.1 Framing</a></li>
</ul>
</section>
</section>
<section id='introduction' class="informative">
<h1>Introduction</h1>
<p>JSON-LD is a lightweight syntax to serialize Linked Data [[LINKED-DATA]] in JSON [[RFC8259]].
Its design allows existing JSON to be interpreted as Linked Data with minimal changes.
As with other representations of Linked Data which describe directed graphs,
a single directed graph can have many different serializations, each expressing
exactly the same information. Developers typically work with trees, represented as
<a>JSON objects</a>. While mapping a graph to
a tree can be done, the layout of the end result must be specified in advance.
A <a>Frame</a> can be used by a developer on a JSON-LD document to
specify a deterministic layout for a graph.</p>
<p>Using delimiters around a chunk of data is known as "framing".
JSON-LD uses JSON delimiters such as <code>{</code> and <code>}</code> to
separate statements about a particular subject. JSON-LD also allows subjects
to reference other subjects through the use of their identifiers, expressed
as strings.</p>
<p>However, given that JSON-LD represents one or more <a>graphs</a> of information,
there is more than one way to frame the statements about several related
subjects into a whole document. In fact, a graph of information can be
thought of as a long list of independent statements (aka <a>triples</a>) that are not bundled together in any way.</p>
<p>The
<a href="#the-application-programming-interface" class="sectionRef">JSON-LD Framing API</a>
enables a developer to specify exactly how they would like data to be framed,
such that statements about a particular subject are bundled together,
delimited via <code>{</code> and <code>}</code>, and such that the subjects
they relate to "nest" into a particular tree structure that matches what
their application expects.</p>
<section class="informative">
<h2>How to Read this Document</h2>
<p>This document is a detailed specification for a serialization of Linked
Data in JSON. The document is primarily intended for the following audiences:</p>
<ul>
<li>Authors who want to query JSON-LD documents to create representations
more appropriate for a given use case.</li>
<li>Software developers that want to implement <a>processors</a> and APIs for JSON-LD.</li>
</ul>
<p>A companion document, the JSON-LD 1.1 specification
[[JSON-LD11]], specifies the grammar of JSON-LD documents.</p>
<p>To understand the basics in this specification you must first be familiar with
<a data-cite="RFC8259" data-no-xref="">JSON</a>, which is detailed in [[RFC8259]].
You must also understand the JSON-LD 1.1 Syntax specification [[JSON-LD11]],
which is the base syntax used by all of the algorithms in this document,
and the JSON-LD 1.1 API [[JSON-LD11-API]].
To understand the API and how it is intended to operate in a programming environment,
it is useful to have working knowledge of
the JavaScript programming language [[ECMASCRIPT]]
and WebIDL [[WEBIDL]].
To understand how JSON-LD maps to RDF, it is helpful to be
familiar with the basic RDF concepts [[RDF11-CONCEPTS]].</p>
<p>This document can highlight changes since the [[[JSON-LD10]]] version.
Select to <button class="show-changes"></button> changes.</p>
</section>
<section class="informative">
<h2>Contributing</h2>
<p>There are a number of ways that one may participate in the development of
this specification:</p>
<ul>
<li>Technical discussion typically occurs on the public mailing list:
<a href="https://lists.w3.org/Archives/Public/public-json-ld-wg/">public-json-ld-wg@w3.org</a></li>
<li>The working group uses <a href="https://irc.w3.org/?channels=json-ld">#json-ld</a>
IRC channel is available for real-time discussion on <a href="https://irc.w3.org">irc.w3.org</a>.</li>
<li>The <a href="https://webchat.freenode.net/?channels=json-ld">#json-ld</a>
IRC channel is also available for real-time discussion on irc.freenode.net.</li>
</ul>
</section>
<section class="informative">
<h2>Typographical conventions</h2>
<div data-include="common/typographical-conventions.html"></div>
</section>
<section class="normative">
<h2>Terminology</h2>
<p>This document uses the following terms as defined in external specifications
and defines terms specific to JSON-LD.</p>
<div data-include="common/terms.html"></div>
<section>
<h4>Algorithm Terms</h4>
<p>The Following terms are used within specific algorithms.</p>
<div data-include="common/algorithm-terms.html"></div>
</section>
</section>
<section id="framing-keywords">
<h2>Syntax Tokens and Keywords</h2>
<p>This specification adds a number of <a>keywords</a> (<dfn>framing keywords</dfn>) to
the ones defined in the JSON-LD 1.1 Syntax specification [[JSON-LD11]]:</p>
<dl data-sort>
<dt><code>@default</code></dt>
<dd>Used in <a href="#framing">Framing</a> to set the default value for
an output property when the framed <a>node object</a> does not include such a property.</dd>
<dt><code>@embed</code></dt>
<dd>Used in <a href="#framing">Framing</a> to override the
value of <a>object embed flag</a> within a specific frame. Valid values for
<code>@embed</code> as the following:
<dl data-sort>
<dt><code>@always</code></dt><dd>
Always embed <a>node objects</a> as property values, unless this would
cause a circular reference.
</dd>
<dt class="changed"><code>@once</code></dt><dd class="changed">
Just a single value within a given <a>node object</a> should be embedded,
other values of other properties use a <a>node reference</a>. This is the
default value if neither <code>@embed</code> nor <a>object embed flag</a>
is specified.
<div class="note">The specific <a>node object</a> chosen to embed depends on
ordering. If the {{JsonLdOptions/ordered}} flag is <code>true</code>,
this will be the first <a>node object</a> encountered,
otherwise, it may be any node object.</div>
</dd>
<dt><code>@never</code></dt><dd>
Always use a <a>node reference</a> when serializing matching values.
</dd>
</dl>
<p>Any other value for <code>@embed</code> is invalid and indicates that an
<a data-link-for="JsonLdFramingErrorCode">invalid @embed value</a>
error has been detected and processing is aborted.</p>
</dd>
<dt><code>@explicit</code></dt>
<dd>Used in <a href="#framing">Framing</a> to override the
value of <a>explicit inclusion flag</a> within a specific frame.</dd>
<dt><code>@null</code></dt>
<dd>Used in <a href="#framing">Framing</a> when a value of <code>null</code>
should be returned, which would otherwise be removed when
<a data-cite="JSON-LD11-API#compaction">Compacting</a>.</dd>
<dt><code>@omitDefault</code></dt>
<dd>Used in <a href="#framing">Framing</a> to override the
value of <a>omit default flag</a> within a specific frame.
</dd>
<dt class="changed"><code>@requireAll</code></dt>
<dd class="changed">Used in <a href="#framing">Framing</a> to override the
value of <a>require all flag</a> within a specific frame.</dd>
</dl>
<p>All JSON-LD tokens and keywords are case-sensitive.</p>
</section>
</section>
<section class="informative">
<h2>Features</h2>
<p class="changed">JSON-LD 1.1 introduces new features that are
compatible with [[[JSON-LD10]]] [[JSON-LD10]],
but if processed by a JSON-LD 1.0 processor may produce different results.
Processors default to `json-ld-1.1`, unless the
{{JsonLdOptions/processingMode}} API option
is explicitly set to `json-ld-1.0`.
Publishers are encouraged to use the <code>@version</code> <a>map entry</a> within a <a>context</a>
set to `1.1` to ensure that JSON-LD 1.0 processors will not misinterpret JSON-LD 1.1 features.</p>
<section class="informative">
<h3>Framing</h3>
<p><dfn class="lint-ignore">Framing</dfn> is used to shape the data in a <a>JSON-LD document</a>,
using an example <a>frame</a> document which is used to both match the
<a data-cite="JSON-LD11-API#dfn-flattened">flattened</a>
data and show an example of how the resulting data should be shaped.
Matching is performed by using <a>properties</a> present in in the <a>frame</a>
to find objects in the data that share common values. Matching can be done
either using all properties present in the frame, or any property in the frame.
By chaining together objects using matched property values, objects can be embedded
within one another.</p>
<p>A <a>frame</a> also includes a <a>context</a>, which is used for compacting the resulting
framed output.</p>
<p>For example, assume the following JSON-LD frame:</p>
<pre id="sample-library-frame"
class="example frame" data-transform="updateExample"
data-content-type="application/ld+json;profile=http://www.w3.org/ns/json-ld#frame"
data-frame-for="Flattened library objects"
title="Sample library frame">
<!--
{
"@context": {"@vocab": "http://example.org/"},
"@type": "Library",
"contains": {
"@type": "Book",
"contains": {
"@type": "Chapter"
}
}
}
-->
</pre>
<p>This <a>frame</a> document describes an embedding structure that would place
objects with type <em>Library</em> at the top, with objects of
type <em>Book</em> that were linked to the library object using
the <em>contains</em> property embedded as property values. It also
places objects of type <em>Chapter</em> within the referencing <em>Book</em> object
as embedded values of the <em>Book</em> object.</p>
<p>When using a flattened set of objects that match the frame components:</p>
<pre id="flattened-library-objects"
class="example input" data-transform="updateExample"
title="Flattened library objects">
<!--
{
"@context": {
"@vocab": "http://example.org/",
"contains": {"@type": "@id"}
},
"@graph": [{
"@id": "http://example.org/library",
"@type": "Library",
"location": "Athens",
"contains": "http://example.org/library/the-republic"
}, {
"@id": "http://example.org/library/the-republic",
"@type": "Book",
"creator": "Plato",
"title": "The Republic",
"contains": "http://example.org/library/the-republic#introduction"
}, {
"@id": "http://example.org/library/the-republic#introduction",
"@type": "Chapter",
"description": "An introductory chapter on The Republic.",
"title": "The Introduction"
}]
}
-->
</pre>
<p>The Frame Algorithm can create a new document which follows the structure
of the frame:</p>
<aside id="framed-library-objects"
class="example ds-selector-tabs"
title="Framed library objects">
<div class="selectors">
<a class="playground"
data-result-for="#flattened-library-objects"
data-frame="#sample-library-frame"
target="_blank"
href="">PG</a>
</div>
<pre class="selected framed result" data-transform="updateExample"
data-frame="Sample library frame"
data-result-for="Flattened library objects">
<!--
{
"@context": {"@vocab": "http://example.org/"},
"@id": "http://example.org/library",
"@type": "Library",
"location": "Athens",
"contains": {
"@id": "http://example.org/library/the-republic",
"@type": "Book",
"creator": "Plato",
"title": "The Republic",
"contains": {
"@id": "http://example.org/library/the-republic#introduction",
"@type": "Chapter",
"description": "An introductory chapter on The Republic.",
"title": "The Introduction"
}
}
}
-->
</pre>
</aside>
<p>If <a>processing mode</a> is not <code>json-ld-1.0</code>, or the <a>omit graph flag</a> is <code>true</code>,
the top-level <code>@graph</code> <a>entry</a> may be omitted.</p>
<pre class="example result" data-transform="updateExample"
data-frame="Sample library frame"
data-result-for="Flattened library objects"
title="Framed library objects">
<!--
{
"@context": {"@vocab": "http://example.org/"},
"@id": "http://example.org/library",
"@type": "Library",
"location": "Athens",
"contains": {
"@id": "http://example.org/library/the-republic",
"@type": "Book",
"creator": "Plato",
"title": "The Republic",
"contains": {
"@id": "http://example.org/library/the-republic#introduction",
"@type": "Chapter",
"description": "An introductory chapter on The Republic.",
"title": "The Introduction"
}
}
}
-->
</pre>
<p>The <a href="#framing-algorithm">Framing Algorithm</a> does this by
first expanding both the input frame and document. It then creates
a <a>map of flattened subjects</a>. The outer-most <a>node object</a> within the frame
is used to match objects in the map, in this case looking for <a>node objects</a>
which have an <code>@type</code> of <code>Library</code>, and a
<code>contains</code> property with another
frame used to match values of that property. The input document contains
exactly one such <a>node object</a>. The value of contains also has
a <a>node object</a>, which is then treated as a frame to match the set of <a>subjects</a>
which are <code>contains</code> values of the <code>Library</code> object, and so forth.</p>
<section class="informative"><h4>Matching on Properties</h4>
<p>In addition to matching on types, a frame can match on
one or more properties.</p>
<p>For example, the following frame selects object based on property
values, rather than `@type`.</p>
<pre id="library-frame-with-property-selection"
class="example frame nohighlight" data-transform="updateExample"
data-content-type="application/ld+json;profile=http://www.w3.org/ns/json-ld#frame"
data-frame-for="Flattened library objects"
title="Library frame with property matching">
<!--
{
"@context": {"@vocab": "http://example.org/"},
****"location": "Athens"****,
"contains": {
****"title": "The Republic"****,
"contains": {
****"title": "The Introduction"****
}
}
}
-->
</pre>
<p>This will generate the same framed results as when selecting on `@type`,
as the property values are unique to each node <a>object</a>.</p>
<aside class="example ds-selector-tabs"
title="Framed library objects with property matching">
<div class="selectors">
<a class="playground"
data-result-for="#flattened-library-objects"
data-frame="#library-frame-with-property-selection"
target="_blank"
href="">PG</a>
</div>
<pre class="selected framed result" data-transform="updateExample"
data-frame="Library frame with property matching"
data-result-for="Flattened library objects">
<!--
{
"@context": {"@vocab": "http://example.org/"},
"@id": "http://example.org/library",
"@type": "Library",
"location": "Athens",
"contains": {
"@id": "http://example.org/library/the-republic",
"@type": "Book",
"creator": "Plato",
"title": "The Republic",
"contains": {
"@id": "http://example.org/library/the-republic#introduction",
"@type": "Chapter",
"description": "An introductory chapter on The Republic.",
"title": "The Introduction"
}
}
}
-->
</pre>
</aside>
<p>See <a href="#require-all-flag" class="sectionRef"></a>
to see how matching can be restricted to match <a>node objects</a> containing
all, versus any such listed property.</p>
</section>
<section class="informative"><h4>Wildcard Matching</h4>
<p>The empty <a>map</a> (`{}`) is used as a <a>wildcard</a>, which will
match a property if it exists in a target <a>node object</a>, independent of any specific value.</p>
<p>For example, the following frame selects object based on property
wildcarding, rather than `@type`.</p>
<pre id="library-frame-with-wildcards"
class="example frame nohighlight" data-transform="updateExample"
data-content-type="application/ld+json;profile=http://www.w3.org/ns/json-ld#frame"
data-frame-for="Flattened library objects"
title="Library frame with wildcard matching">
<!--
{
"@context": {"@vocab": "http://example.org/"},
****"location": {}****,
"contains": {
****"creator": {}****,
"contains": {
****"description": {}****
}
}
}
-->
</pre>
<p>This will generate the same framed results as when selecting on `@type`,
as the matched properties are distinct to each <a>node object</a>.</p>
<aside class="example ds-selector-tabs"
title="Framed library objects with wildcard matching">
<div class="selectors">
<a class="playground"
data-result-for="#flattened-library-objects"
data-frame="#library-frame-with-wildcards"
target="_blank"
href="">PG</a>
</div>
<pre class="selected framed result" data-transform="updateExample"
data-frame="Library frame with wildcard matching"
data-result-for="Flattened library objects">
<!--
{
"@context": {"@vocab": "http://example.org/"},
"@id": "http://example.org/library",
"@type": "Library",
"location": "Athens",
"contains": {
"@id": "http://example.org/library/the-republic",
"@type": "Book",
"creator": "Plato",
"title": "The Republic",
"contains": {
"@id": "http://example.org/library/the-republic#introduction",
"@type": "Chapter",
"description": "An introductory chapter on The Republic.",
"title": "The Introduction"
}
}
}
-->
</pre>
</aside>
</section>
<section class="informative"><h4>Match on the Absence of a Property</h4>
<p>The empty <a>array</a> (`[]`) is used for <a>match none</a>, which will
match a node object only if a property does not exist in a target <a>node object</a>.</p>
<p>For example, the following frame selects object based on the absence of properties,
rather than `@type`.</p>
<pre id="library-frame-with-absent-property"
class="example frame nohighlight" data-transform="updateExample"
data-content-type="application/ld+json;profile=http://www.w3.org/ns/json-ld#frame"
data-frame-for="Flattened library objects"
title="Library frame with absent matching">
<!--
{
"@context": {"@vocab": "http://example.org/"},
****"creator": []****,
****"title": []****,
"contains": {
****"location": []****,
****"description": []****,
"contains": {
****"location": []****
}
}
}
-->
</pre>
<p>This will generate the same framed results as when selecting on `@type`,
the property that is excluded uniquely identifies each <a>node object</a>.
Note that additional properties with the value `null` are added
for those properties explicitly excluded.</p>
<aside class="example ds-selector-tabs"
title="Framed library objects with wildcard matching">
<div class="selectors">
<a class="playground"
data-result-for="#flattened-library-objects"
data-frame="#library-frame-with-absent-property"
target="_blank"
href="">PG</a>
</div>
<pre class="selected framed result" data-transform="updateExample"
data-frame="Library frame with absent matching"
data-result-for="Flattened library objects">
<!--
{
"@context": {"@vocab": "http://example.org/"},
"@id": "http://example.org/library",
"@type": "Library",
"location": "Athens",
****"creator": null****, ####← This property is added####
****"title": null****, ####← This property is added####
"contains": {
"@id": "http://example.org/library/the-republic",
"@type": "Book",
"creator": "Plato",
****"description": null****, ####← This property is added####
****"location": null****, ####← This property is added####
"title": "The Republic",
"contains": {
"@id": "http://example.org/library/the-republic#introduction",
"@type": "Chapter",
"description": "An introductory chapter on The Republic.",
****"location": null****, ####← This property is added####
"title": "The Introduction"
}
}
}
-->
</pre>
</aside>
</section>
<section class="informative"><h4>Matching on Values</h4>
<p>Frames can be matched based on the presence of specific property values.
These values can themselves use <a>wildcards</a>, to match on a specific
or set of values, <a>language tags</a>, types, or <a data-lt="base direction">base direction</a>.</p>
<p>For an example, we'll use an multilingual version of the library example
with more complex value representations.</p>
<pre id="multilingual-library-objects"
class="example input" data-transform="updateExample"
title="Multilingual library objects">
<!--
{
"@context": {
"@vocab": "http://example.org/",
"contains": {"@type": "@id"}
},
"@graph": [{
"@id": "http://example.org/library",
"@type": "Library",
"location": [
{"@value": "Athens", "@language": "en"},
{"@value": "Αθήνα", "@language": "grc"},
{"@value": "Athína", "@language": "el-Latn"}
],
"contains": "http://example.org/library/the-republic"
}, {
"@id": "http://example.org/library/the-republic",
"@type": "Book",
"creator": [
{"@value": "Plato", "@language": "en"},
{"@value": "Πλάτων", "@language": "grc"},
{"@value": "Plátōn", "@language": "el-Latn"}
],
"title": [
{"@value": "The Republic", "@language": "en"},
{"@value": "Πολιτεία", "@language": "grc"},
{"@value": "Res Publica", "@language": "el-Latn"}
],
"contains": "http://example.org/library/the-republic#introduction"
}, {
"@id": "http://example.org/library/the-republic#introduction",
"@type": "Chapter",
"description": "An introductory chapter on The Republic.",
"title": "The Introduction"
}]
}
-->
</pre>
<p>By matching on an attribute of a value, we can match frames
having that attribute, and limit results to property values
that match. In this case, we'll frame the Library and Book objects
on values only in latinized Greek (`el-Latn`):</p>
<pre id="library-frame-with-language-matching"
class="example frame nohighlight" data-transform="updateExample"
data-content-type="application/ld+json;profile=http://www.w3.org/ns/json-ld#frame"
data-frame-for="Multilingual library objects"
title="Library frame with language matching">
<!--
{
"@context": {"@vocab": "http://example.org/"},
"location": {"@value": {}, "@language": "el-Latn"},
"contains": {
"creator": {"@value": {}, "@language": "el-Latn"},
"title": {"@value": {}, "@language": "el-Latn"},
"contains": {
"title": "The Introduction"
}
}
}
-->
</pre>
<p>This generates the following framed results:</p>
<aside class="example ds-selector-tabs"
title="Framed library objects with wildcard matching">
<div class="selectors">
<a class="playground"
data-result-for="#multilingual-library-objects"
data-frame="#library-frame-with-language-matching"
target="_blank"
href="">PG</a>
</div>
<!-- ignore as this won't match the input -->
<pre class="selected framed result" data-transform="updateExample"
data-frame="Library frame with language matching"
data-result-for="Multilingual library objects"
data-ignore>
<!--
{
"@context": {"@vocab": "http://example.org/"},
"@id": "http://example.org/library",
"@type": "Library",
"location": {"@value": "Athína", "@language": "el-Latn"},
"contains": {
"@id": "http://example.org/library/the-republic",
"@type": "Book",
"creator": {"@value": "Plátōn", "@language": "el-Latn"},
"title": {"@value": "Res Publica", "@language": "el-Latn"},
"contains": {
"@id": "http://example.org/library/the-republic#introduction",
"@type": "Chapter",
"description": "An introductory chapter on The Republic.",
"title": "The Introduction"
}
}
}
-->
</pre>
</aside>
</section>
<section class="informative"><h4>Matching on `@id`</h4>
<p>Frames can be matched if they match a specific
identifier (`@id`). This can be illustrated with the original
<a href="#flattened-library-objects">Flattened library objects</a>
input using a frame which matches on specific `@id` values:</p>
<pre id="library-frame-with-id-matching"
class="example frame nohighlight" data-transform="updateExample"
data-content-type="application/ld+json;profile=http://www.w3.org/ns/json-ld#frame"
data-frame-for="Flattened library objects"
title="Library frame with @id matching">
<!--
{
"@context": {"@vocab": "http://example.org/"},
"@id": "http://example.org/library",
"contains": {
"@id": "http://example.org/library/the-republic",
"contains": {
"@id": "http://example.org/library/the-republic#introduction"
}
}
}
-->
</pre>
<p>This generates the following framed results:</p>
<aside class="example ds-selector-tabs"
title="Framed library objects with @id matching">