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<p>
<small>This page is taken from <a href="http://docs.api.talis.com/platform-api/output-types/rdf-json">The Talis Systems documentation for RDF/JSON</a>.
© Talis Systems Ltd. 2011. The content is available under
<a href="http://creativecommons.org/licenses/by-sa/3.0/" target="">Attribution-Share Alike 3.0</a>
</small> license.
</p>
<h1>RDF JSON</h1>
<p><a href="http://json.org/">JSON</a> (the serialisation of data
in javascript object notation) is an increasingly popular data format,
largely because it is easy to parse (or, in the case of javascript, simply
evaluate) into a data structure of the consumer's programming language of
choice.</p>
<p>This is a specification for a resource-centric serialisation of RDF in
JSON. It aims to serialise RDF in a structure that is easy for developers
to work with.</p>
<h2>SyntaxSpecification</h2>
<p>RDF/JSON represents a set of RDF triples as a series of nested data structures.
Each unique subject in the set of triples is represented as a key in
JSON object (also known as associative array, dictionary or hash table).
The value of each key is a object whose keys are the URIs of the
properties associated with each subject. The value of each property key
is an array of objects representing the value of each property.</p>
<p>Blank node subjects are named using a string conforming to the <a href="http://www.dajobe.org/2004/01/turtle/#nodeID">nodeID production in Turtle</a>. For example:
_:A1</p>
<p>In general, a triple (subject <b>S</b>, predicate <b>P</b>, object <b>O</b>) is encoded in the following
structure:</p>
<pre>{ "S" : { "P" : [ O ] } }</pre>
<p>The object of the triple <b>O</b> is represented as a further JSON object with the following
keys:</p>
<dl>
<dt>type</dt>
<dd>one of 'uri', 'literal' or 'bnode' (<b>required</b>
and must be lowercase)</dd>
<dt>value</dt>
<dd>the lexical value of the
object (<b>required</b>, full URIs should be used, not
qnames)</dd>
<dt>lang</dt>
<dd>the language of a literal value
(<b>optional</b> but if supplied it must not be
empty)</dd>
<dt>datatype</dt>
<dd>the datatype URI of the literal value (<b>optional</b>)</dd>
</dl>
<p>The 'lang' and 'datatype' keys should only be used if the value of the 'type' key is "literal".</p>
<p>For example, the following triple:</p>
<pre>&lt;http://example.org/about&gt; &lt;http://purl.org/dc/elements/1.1/title&gt; "Anna's Homepage" .</pre>
<p>can be encoded in RDF/JSON as:</p>
<pre>{
"http://example.org/about" :
{
"http://purl.org/dc/elements/1.1/title": [ { "type" : "literal" , "value" : "Anna's Homepage" } ]
}
}</pre>
<p>Here is an example of the RDF JSON specification in the format of
a <a href="http://json-schema.org/">JSON Schema</a>. The latest version can
also be found in the <a href="http://soapjr.org/schemas/RDF_JSON">schema
section</a> of the <a href="http://soapjr.org/">SOAPjr.org site</a>.</p>
<pre>{
"version":"0.3.0",
"id":"RDF-JSON",
"description":"RDF JSON definition",
"type":"object",
"properties":{
},
"additionalProperties":{
"type":"object",
"description":"subject (root object)",
"optional":"true",
"properties":{
},
"additionalProperties":{
"type":"array",
"description":"predicate (subject object)",
"optional":"true",
"items":{
"type":"object",
"description":"object (value array)",
"properties":{
"description":"content (value object)",
"type":{
"type":"string",
"enum":["uri","bnode","literal"]
},
"value":{
"type":"string"
},
"lang":{
"optional":true,
"description":"See ftp://ftp.isi.edu/in-notes/bcp/bcp47.txt",
"type":"string"
},
"datatype":{
"optional":true,
"format":"uri",
"type":"string"
}
}
}
}
}
}
</pre>
<h2>Examples</h2>
<p>The following RDF/XML:</p>
<pre>&lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:foaf="http://xmlns.com/foaf/0.1/"
xmlns:dc="http://purl.org/dc/elements/1.1/"&gt;
&lt;rdf:Description rdf:about="http://example.org/about"&gt;
&lt;dc:creator&gt;Anna Wilder&lt;/dc:creator&gt;
&lt;dc:title xml:lang="en"&gt;Anna's Homepage&lt;/dc:title&gt;
&lt;foaf:maker rdf:nodeID="person" /&gt;
&lt;/rdf:Description&gt;
&lt;rdf:Description rdf:nodeID="person"&gt;
&lt;foaf:homepage rdf:resource="http://example.org/about" /&gt;
&lt;foaf:made rdf:resource="http://example.org/about" /&gt;
&lt;foaf:name&gt;Anna Wilder&lt;/foaf:name&gt;
&lt;foaf:firstName&gt;Anna&lt;/foaf:firstName&gt;
&lt;foaf:surname&gt;Wilder&lt;/foaf:surname&gt;
&lt;foaf:depiction rdf:resource="http://example.org/pic.jpg" /&gt;
&lt;foaf:nick&gt;wildling&lt;/foaf:nick&gt;
&lt;foaf:nick&gt;wilda&lt;/foaf:nick&gt;
&lt;foaf:mbox_sha1sum&gt;69e31bbcf58d432950127593e292a55975bc66fd&lt;/foaf:mbox_sha1sum&gt;
&lt;/rdf:Description&gt;
&lt;/rdf:RDF&gt;</pre>
<p>Can be represented as the following RDF/JSON structure:</p><pre>{
"http://example.org/about" : {
"http://purl.org/dc/elements/1.1/creator" : [ { "value" : "Anna Wilder", "type" : "literal" } ],
"http://purl.org/dc/elements/1.1/title" : [ { "value" : "Anna's Homepage", "type" : "literal", "lang" : "en" } ] ,
"http://xmlns.com/foaf/0.1/maker" : [ { "value" : "_:person", "type" : "bnode" } ]
} ,
"_:person" : {
"http://xmlns.com/foaf/0.1/homepage" : [ { "value" : "http://example.org/about", "type" : "uri" } ] ,
"http://xmlns.com/foaf/0.1/made" : [ { "value" : "http://example.org/about", "type" : "uri" } ] ,
"http://xmlns.com/foaf/0.1/name" : [ { "value" : "Anna Wilder", "type" : "literal" } ] ,
"http://xmlns.com/foaf/0.1/firstName" : [ { "value" : "Anna", "type" : "literal" } ] ,
"http://xmlns.com/foaf/0.1/surname" : [ { "value" : "Wilder", "type" : "literal" } ] ,
"http://xmlns.com/foaf/0.1/depiction" : [ { "value" : "http://example.org/pic.jpg", "type" : "uri" } ] ,
"http://xmlns.com/foaf/0.1/nick" : [
{ "type" : "literal", "value" : "wildling"} ,
{ "type" : "literal", "value" : "wilda" }
] ,
"http://xmlns.com/foaf/0.1/mbox_sha1sum" : [ { "value" : "69e31bbcf58d432950127593e292a55975bc66fd", "type" : "literal" } ]
}
}</pre>
<h2>Serialisation Algorithm</h2>
<p>Refer to <a href="http://json.org/">http://json.org/</a> for definitions of
terminology</p>
<ol>
<li>Start a JSON object (called the root object)</li>
<li>Group all the triples by subject</li>
<li>For each subject:
<ol>
<li>Create a JSON object for the subject (called the subject
object)</li>
<li>Group all triples having the current subject by predicate</li>
<li>For each predicate:<ol>
<li>Create a JSON array (called the value array)</li>
<li>Select all triples having the current subject and current
predicate</li>
<li>For each value:
<ol>
<li>Create a JSON object (called the value object)</li>
<li>Add a key/value pair to the value object with the key
being the string "value" and the value being the lexical
value of the triple value</li>
<li>Add a key/value pair to
the value object with the key being the string "type" and
the value being one of "literal", "uri" or "bnode"
depending on the type of the triple's value</li>
#content
<li>If the triple's value is a plain literal and has a
language then add a key/value pair to the value object with the key being
the string "lang" and the value being the language token</li>
<li>If the triple's value is a typed literal then add a
key/value pair to the value object with the key being the string
"datatype" and value being the URI of the datatype</li>
<li>Push the value object onto the end of the value array</li>
</ol>
</li>
<li>Add a key/value pair to the subject object with the key being the predicate URI and the value being the value
array</li>
</ol>
</li>
<li>Add a key/value pair to the root object with the key being the
URI or blank node identifier of the subject and the value being the
subject object created in the previous step</li>
</ol>
</li>
</ol>
<!--
<h3>Further Examples</h3>
<p>RDF/XML can be converted into the specified RDF/JSON format by using
the <a href="http://convert.test.talis.com/">http://convert.test.talis.com</a>
web service.</p>
-->
<h2>Publishing RDF/JSON on the web</h2>
<p>If doing content-negotiation, respond to, and send the content-type
as <code>application/json</code>. An empty graph (ie: no triples) should
be served as an empty object: <code>{}</code>.</p>
<h2>References</h2>
<ol>
<li><a href="http://www.ietf.org/rfc/rfc3066.txt">Tags
for the Identification of
Languages</a></li>
<li><a href="http://docs.api.talis.com/system/errors/NodeNotFound?suri=wuid:gx:785d2e15fb97c7a4">RDF JSON
Brainstorming</a></li>
<li><a href="http://json.org/">http://json.org/</a></li>
<li><a href="http://www.ietf.org/rfc/rfc3986.txt">Uniform
Resource Identifier (URI): Generic
Syntax</a>
</li>
</ol>
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