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<h1 class="title">Support of RDF-star</h1>
<main class="d-flex flex-xl-row flex-column">
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<h2 class="h6 sticky-top m-0 p-2 bg-body-tertiary">On this page</h2>
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<ul>
<li><a href="#rdf-star">RDF-star</a></li>
<li><a href="#sparql-star">SPARQL-star</a>
<ul>
<li><a href="#sparql-functions-related-to-quoted-triples">SPARQL Functions related to quoted triples</a></li>
<li><a href="#sparql-results">SPARQL results</a></li>
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<li><a href="#model-api">Model API</a></li>
<li><a href="#reification">Reification</a></li>
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<p><a href="https://w3c.github.io/rdf-star/">RDF-star</a> is an extension to RDF that provides
a way for one triple to refer to another triple. RDF* is the name of the
original work which is described in
<a href="https://blog.liu.se/olafhartig/2019/01/10/position-statement-rdf-star-and-sparql-star/">Olaf Hartig&rsquo;s blog entry</a>.</p>
<p>Example:</p>
<div class="highlight"><pre tabindex="0" style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-turtle" data-lang="turtle"><span style="display:flex;"><span><span style="">&lt;&lt;</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">john</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">foaf:</span><span style="color:#008000;font-weight:bold">name</span><span style="color:#bbb"> </span><span style="color:#b44">&#34;John Smith&#34;</span><span style="color:#bbb"> </span><span style="">&gt;&gt;</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dct:</span><span style="color:#008000;font-weight:bold">source</span><span style="color:#bbb"> </span><span style="color:#b8860b">&lt;http://example/directory&gt;</span><span style="color:#bbb"> </span>.<span style="color:#bbb">
</span></span></span></code></pre></div><p>The part <code>&lt;&lt; :john foaf:name &quot;John Smith&quot; &gt;&gt;</code> is a quoted triple and refers to the triple with subject <code>:john</code>, property <code>foaf:name</code> and object <code>&quot;John Smith&quot;</code>.</p>
<p>Triple terms can be in the subject or object position.</p>
<p>Jena provides support for RDF-star and the related SPARQL-star.</p>
<ul>
<li>Turtle, N-Triples, TriG and N-Quads extended for Triple Terms syntax,
input and output. There is no output in RDF/XML.</li>
<li>SPARQL extended with Triple Term syntax for graph matching.</li>
<li>SPARQL Result formats for JSON and XML extended to support quoted triples in results.</li>
<li>Support in the Model API.</li>
<li>Translation to and from RDF reification.</li>
</ul>
<p>All this is active by default in Fuseki.</p>
<p>The aim is to follow the definition of the <a href="https://w3c.github.io/rdf-star/">RDF-star community</a>.</p>
<p>Storage in databases <a href="/documentation/tdb">TDB1</a> and <a href="/documentation/tdb2/">TDB2</a>
as well as in-memory databases is supported.</p>
<h2 id="rdf-star">RDF-star</h2>
<p>RDF-star syntax for quoted triples is added to the parsers for Turtle, N-Triples, TriG and N-Quads.</p>
<p>Datasets may have graphs that have quoted triples that refer to triples anywhere, not just in the same graph.</p>
<h2 id="sparql-star">SPARQL-star</h2>
<p>Matches for quoted triples:</p>
<div class="highlight"><pre tabindex="0" style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-sparql" data-lang="sparql"><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">SELECT</span> <span style="color:#b8860b">?name</span> { <span style="color:#666">&lt;&lt;</span>:<span style="color:#008000;font-weight:bold">john</span> <span style="color:#00f;font-weight:bold">foaf</span>:<span style="color:#008000;font-weight:bold">name</span> <span style="color:#b8860b">?name</span> <span style="color:#666">&gt;&gt;</span> <span style="color:#00f;font-weight:bold">dct</span>:<span style="color:#008000;font-weight:bold">source</span> <span style="color:#a0a000">&lt;http://example/directory&gt;</span> }
</span></span></code></pre></div><p>Insert triples terms into the default graph to record the graph source.</p>
<div class="highlight"><pre tabindex="0" style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-sparql" data-lang="sparql"><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">INSERT</span> { <span style="color:#666">&lt;&lt;</span><span style="color:#b8860b">?s</span> <span style="color:#b8860b">?p</span> <span style="color:#b8860b">?o</span><span style="color:#666">&gt;&gt;</span> <span style="color:#00f;font-weight:bold">dct</span>:<span style="color:#008000;font-weight:bold">source</span> <span style="color:#a0a000">&lt;http://example/directory&gt;</span> }
</span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">WHERE</span> {
</span></span><span style="display:flex;"><span> <span style="color:#a2f;font-weight:bold">GRAPH</span> <span style="color:#a0a000">&lt;http://example/directory&gt;</span> {
</span></span><span style="display:flex;"><span> <span style="color:#b8860b">?s</span> <span style="color:#b8860b">?p</span> <span style="color:#b8860b">?o</span>
</span></span><span style="display:flex;"><span> }
</span></span><span style="display:flex;"><span>}
</span></span></code></pre></div><p>Use in expressions:</p>
<div class="highlight"><pre tabindex="0" style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-sparql" data-lang="sparql"><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">SELECT</span> <span style="color:#b8860b">?t</span> {
</span></span><span style="display:flex;"><span> <span style="color:#b8860b">?s</span> <span style="color:#b8860b">?p</span> <span style="color:#b8860b">?o</span>
</span></span><span style="display:flex;"><span> <span style="color:#a2f;font-weight:bold">BIND</span>(<span style="color:#666">&lt;&lt;</span> <span style="color:#b8860b">?s</span> <span style="color:#b8860b">?p</span> <span style="color:#b8860b">?o</span><span style="color:#666">&gt;&gt;</span> <span style="color:#a2f;font-weight:bold">AS</span> <span style="color:#b8860b">?t</span>)
</span></span><span style="display:flex;"><span>}
</span></span></code></pre></div><div class="highlight"><pre tabindex="0" style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-sparql" data-lang="sparql"><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">SELECT</span> (<span style="color:#666">&lt;&lt;</span> <span style="color:#b8860b">?s</span> <span style="color:#b8860b">?p</span> <span style="color:#b8860b">?o</span><span style="color:#666">&gt;&gt;</span> <span style="color:#a2f;font-weight:bold">AS</span> <span style="color:#b8860b">?t</span>) {
</span></span><span style="display:flex;"><span> <span style="color:#b8860b">?s</span> <span style="color:#b8860b">?p</span> <span style="color:#b8860b">?o</span>
</span></span><span style="display:flex;"><span>}
</span></span></code></pre></div><h3 id="sparql-functions-related-to-quoted-triples">SPARQL Functions related to quoted triples</h3>
<p>These functions cause an expression error if passed the wrong type of arguments.</p>
<table>
<thead>
<tr>
<th>Function</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>TRIPLE(?s, ?p, ?o)</code></td>
<td>Create a quoted triple from s/p/o</td>
</tr>
<tr>
<td><code>isTRIPLE(?t)</code></td>
<td>Return true if the argument value is a quoted triple</td>
</tr>
<tr>
<td><code>SUBJECT(?t)</code></td>
<td>Return the subject of the quoted triple</td>
</tr>
<tr>
<td><code>PREDICATE(?t)</code></td>
<td>Return the predicate (property) of the quoted triple</td>
</tr>
<tr>
<td><code>OBJECT(?t)</code></td>
<td>Return the object of the quoted triple</td>
</tr>
</tbody>
</table>
<h3 id="sparql-results">SPARQL results</h3>
<p>The syntaxes for SPARQL results from a SELECT query, <code>application/sparql-results+json</code>,
<code>application/sparql-results+xml</code> are extended to include quoted triples:</p>
<p>The quoted triple <code>&lt;&lt; _:b0 &lt;http://example/p&gt; 123 &gt;&gt;</code> is encoded, in
<code>application/sparql-results+json</code> as:</p>
<div class="highlight"><pre tabindex="0" style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-json" data-lang="json"><span style="display:flex;"><span> {
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&#34;type&#34;</span>: <span style="color:#b44">&#34;triple&#34;</span> ,
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&#34;value&#34;</span>: {
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&#34;subject&#34;</span>: { <span style="color:#008000;font-weight:bold">&#34;type&#34;</span>: <span style="color:#b44">&#34;bnode&#34;</span> , <span style="color:#008000;font-weight:bold">&#34;value&#34;</span>: <span style="color:#b44">&#34;b0&#34;</span> } ,
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&#34;predicate&#34;</span>: { <span style="color:#008000;font-weight:bold">&#34;type&#34;</span>: <span style="color:#b44">&#34;uri&#34;</span> , <span style="color:#008000;font-weight:bold">&#34;value&#34;</span>: <span style="color:#b44">&#34;http://example/p&#34;</span> } ,
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&#34;object&#34;</span>: { <span style="color:#008000;font-weight:bold">&#34;type&#34;</span>: <span style="color:#b44">&#34;literal&#34;</span> , <span style="color:#008000;font-weight:bold">&#34;datatype&#34;</span>: <span style="color:#b44">&#34;http://www.w3.org/2001/XMLSchema#integer&#34;</span> , <span style="color:#008000;font-weight:bold">&#34;value&#34;</span>: <span style="color:#b44">&#34;123&#34;</span> }
</span></span><span style="display:flex;"><span> }
</span></span></code></pre></div><p>and similarly in <code>application/sparql-results+xml</code>:</p>
<div class="highlight"><pre tabindex="0" style="background-color:#f8f8f8;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-xml" data-lang="xml"><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&lt;triple&gt;</span>
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&lt;subject&gt;</span>
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&lt;bnode&gt;</span>b0<span style="color:#008000;font-weight:bold">&lt;/bnode&gt;</span>
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&lt;/subject&gt;</span>
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&lt;predicate&gt;</span>
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&lt;uri&gt;</span>http://example/p<span style="color:#008000;font-weight:bold">&lt;/uri&gt;</span>
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&lt;/predicate&gt;</span>
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&lt;object&gt;</span>
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&lt;literal</span> <span style="color:#b44">datatype=</span><span style="color:#b44">&#34;http://www.w3.org/2001/XMLSchema#integer&#34;</span><span style="color:#008000;font-weight:bold">&gt;</span>123<span style="color:#008000;font-weight:bold">&lt;/literal&gt;</span>
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&lt;/object&gt;</span>
</span></span><span style="display:flex;"><span> <span style="color:#008000;font-weight:bold">&lt;/triple&gt;</span>
</span></span></code></pre></div><h2 id="model-api">Model API</h2>
<p>RDF-star quoted triples are treated as <code>Resource</code> to preserve the typed Model API.
They occur in the subject and object positions.</p>
<p>A <code>Resource</code> contains a <code>Statement</code> object if the underlying RDF term is an RDF-star quoted triple.</p>
<p>New methods include:</p>
<ul>
<li><code>Statement Resource.getStatement()</code></li>
<li><code>Resource Model.createResource(Statement)</code></li>
<li><code>Resource ResourceFactory.createStatement</code></li>
</ul>
<h2 id="reification">Reification</h2>
<p><code>org.apache.jena.system.RDFStar</code> provides functions to translate RDF-star into
RDF reification, and translate it back again to RDF-star.</p>
<p>Translating back to RDF-star relies on the consistency constraint that there is
only one reification for each unique quoted triple term.</p>
</article>
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