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| <h1 class="title">SPARQL Tutorial - Datasets</h1> |
| |
| |
| <main class="d-flex flex-xl-row flex-column"> |
| |
| <aside class="text-muted align-self-start mb-3 p-0 d-xl-none d-block"> |
| <h2 class="h6 sticky-top m-0 p-2 bg-body-tertiary">On this page</h2> |
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| <ul> |
| <li><a href="#querying-datasets">Querying datasets</a> |
| <ul> |
| <li><a href="#example-data">Example Data</a></li> |
| <li><a href="#accessing-the-dataset">Accessing the Dataset</a></li> |
| <li><a href="#querying-a-specific-graph">Querying a specific graph</a></li> |
| <li><a href="#querying-to-find-data-from-graphs-that-match-a-pattern">Querying to find data from graphs that match a pattern</a></li> |
| </ul> |
| </li> |
| <li><a href="#describing-rdf-datasets---from-and-from-named">Describing RDF Datasets - <code>FROM</code> and <code>FROM NAMED</code></a></li> |
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| <article class="flex-column me-lg-4"> |
| <p>This section covers RDF Datasets - an RDF Dataset is the unit that |
| is queried by a SPARQL query. It consists of a default graph, and a |
| number of named graphs.</p> |
| <h2 id="querying-datasets">Querying datasets</h2> |
| <p>The graph matching operation |
| (<a href="sparql_basic_patterns.html">basic patterns</a>, |
| <a href="sparql_optionals.html"><code>OPTIONAL</code>s</a>, and <a href="sparql_union.html"><code>UNION</code>s</a>) work on |
| one RDF graph. This starts out being the default graph of the |
| dataset but it can be changed by the <code>GRAPH</code> keyword.</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">GRAPH</span> <span style="color:#00a000">uri</span> { ... <span style="">pattern</span> ... } |
| </span></span><span style="display:flex;"><span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">GRAPH</span> <span style="">var</span> { ... <span style="">pattern</span> ... } |
| </span></span></code></pre></div><p>If a URI is given, the pattern will be matched against the graph in |
| the dataset with that name - if there isn’t one, the <code>GRAPH</code> clause |
| fails to match at all.</p> |
| <p>If a variable is given, all the named graphs (not the default |
| graph) are tried. The variable may be used elsewhere so that if, |
| during execution, its value is already known for a solution, only |
| the specific named graph is tried.</p> |
| <h3 id="example-data">Example Data</h3> |
| <p>An RDF dataset can take a variety of forms. Two common setups are |
| to have the default graph being the union (the RDF merge) of all |
| the named graphs or to have the default graph be an inventory of |
| the named graphs (where they came from, when they were read etc). |
| There are no limitations - one graph can be included twice under |
| different names, or some graphs may share triples with others.</p> |
| <p>In the examples below we will use the following dataset that might |
| occur for an RDF aggregator of book details:</p> |
| <p>Default graph (<a href="sparql_data/ds-dft.ttl">ds-dft.ttl</a>):</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="color:#a2f;font-weight:bold">@prefix</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#bbb"> </span><span style="color:#b8860b"><http://purl.org/dc/elements/1.1/></span><span style="color:#bbb"> </span>.<span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="color:#a2f;font-weight:bold">@prefix</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">xsd:</span><span style="color:#bbb"> </span><span style="color:#b8860b"><http://www.w3.org/2001/XMLSchema#></span><span style="color:#bbb"> </span>.<span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="color:#b8860b"><ds-ng-1.ttl></span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">date</span><span style="color:#bbb"> </span><span style="color:#b44">"2005-07-14T03:18:56+0100"</span><span style="color:#666">^^</span><span style="font-style:italic">xsd:dateTime</span><span style="color:#bbb"> </span>.<span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="color:#b8860b"><ds-ng-2.ttl></span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">date</span><span style="color:#bbb"> </span><span style="color:#b44">"2005-09-22T05:53:05+0100"</span><span style="color:#666">^^</span><span style="font-style:italic">xsd:dateTime</span><span style="color:#bbb"> </span>.<span style="color:#bbb"> |
| </span></span></span></code></pre></div><p>Named graph (<a href="sparql_data/ds-ng-1.ttl">ds-ng-1.ttl</a>):</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="color:#a2f;font-weight:bold">@prefix</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#bbb"> </span><span style="color:#b8860b"><http://purl.org/dc/elements/1.1/></span><span style="color:#bbb"> </span>.<span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span>[]<span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">title</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Philospher's Stone"</span><span style="color:#bbb"> </span>.<span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span>[]<span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">title</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Chamber of Secrets"</span><span style="color:#bbb"> </span>.<span style="color:#bbb"> |
| </span></span></span></code></pre></div><p>Named graph (<a href="sparql_data/ds-ng-2.ttl">ds-ng-2.ttl</a>):</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="color:#a2f;font-weight:bold">@prefix</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#bbb"> </span><span style="color:#b8860b"><http://purl.org/dc/elements/1.1/></span><span style="color:#bbb"> </span>.<span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span>[]<span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">title</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Sorcerer's Stone"</span><span style="color:#bbb"> </span>.<span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span>[]<span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">title</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Chamber of Secrets"</span><span style="color:#bbb"> </span>.<span style="color:#bbb"> |
| </span></span></span></code></pre></div><p>That is, we have two small graphs describing some books, and we |
| have a default graph which records when these graphs were last |
| read.</p> |
| <p>Queries can be run with the command line application (this would be |
| all one line):</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-bash" data-lang="bash"><span style="display:flex;"><span>$ java -cp ... arq.sparql |
| </span></span><span style="display:flex;"><span> --graph ds-dft.ttl --namedgraph ds-ng-1.ttl --namedgraph ds-ng-2.ttl |
| </span></span><span style="display:flex;"><span> --query query file |
| </span></span></code></pre></div><p>Datasets don’t have to be created just for the lifetime of the query. |
| They can be created and stored in a database, as would be more |
| usual for an aggregator application.</p> |
| <h3 id="accessing-the-dataset">Accessing the Dataset</h3> |
| <p>The first example just accesses the default graph |
| (<a href="sparql_data/q-ds-1.rq">q-ds-1.rq</a>):</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">PREFIX</span> <span style="color:#00f;font-weight:bold">xsd</span>: <span style="color:#a0a000"><http://www.w3.org/2001/XMLSchema#></span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">PREFIX</span> <span style="color:#00f;font-weight:bold">dc</span>: <span style="color:#a0a000"><http://purl.org/dc/elements/1.1/></span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">PREFIX</span> : <span style="color:#a0a000"><.></span> |
| </span></span><span style="display:flex;"><span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">SELECT</span> <span style="color:#666">*</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></code></pre></div><p>(The “<code>PREFIX : <.></code>” just helps format the output)</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="">----------------------------------------------------------------------</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="">s</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="">p</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="">o</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">======================================================================</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">ds-ng-2</span>.<span style="">ttl</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">date</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"2005-09-22T05:53:05+01:00"</span><span style="color:#666">^^</span><span style="font-style:italic">xsd:dateTime</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">ds-ng-1</span>.<span style="">ttl</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">date</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"2005-07-14T03:18:56+01:00"</span><span style="color:#666">^^</span><span style="font-style:italic">xsd:dateTime</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">----------------------------------------------------------------------</span><span style="color:#bbb"> |
| </span></span></span></code></pre></div><p>This is the default graph only - nothing from the named graphs |
| because they aren’t queried unless explicitly indicated via |
| <code>GRAPH</code>.</p> |
| <p>We can query for all triples by querying the default graph and the |
| named graphs (<a href="sparql_data/q-ds-2.rq">q-ds-2.rq</a>):</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">PREFIX</span> <span style="color:#00f;font-weight:bold">xsd</span>: <span style="color:#a0a000"><http://www.w3.org/2001/XMLSchema#></span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">PREFIX</span> <span style="color:#00f;font-weight:bold">dc</span>: <span style="color:#a0a000"><http://purl.org/dc/elements/1.1/></span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">PREFIX</span> : <span style="color:#a0a000"><.></span> |
| </span></span><span style="display:flex;"><span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">SELECT</span> <span style="color:#666">*</span> |
| </span></span><span style="display:flex;"><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 style="color:#a2f;font-weight:bold">UNION</span> { <span style="color:#a2f;font-weight:bold">GRAPH</span> <span style="color:#b8860b">?g</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><p>giving:</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="">---------------------------------------------------------------------------------------</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="">s</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="">p</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="">o</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="">g</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">=======================================================================================</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">ds-ng-2</span>.<span style="">ttl</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">date</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"2005-09-22T05:53:05+01:00"</span><span style="color:#666">^^</span><span style="font-style:italic">xsd:dateTime</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">ds-ng-1</span>.<span style="">ttl</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">date</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"2005-07-14T03:18:56+01:00"</span><span style="color:#666">^^</span><span style="font-style:italic">xsd:dateTime</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="">_</span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">b0</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">title</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Sorcerer's Stone"</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">ds-ng-2</span>.<span style="">ttl</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="">_</span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">b1</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">title</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Chamber of Secrets"</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">ds-ng-2</span>.<span style="">ttl</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="">_</span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">b2</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">title</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Chamber of Secrets"</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">ds-ng-1</span>.<span style="">ttl</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="">_</span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">b3</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">dc:</span><span style="color:#008000;font-weight:bold">title</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Philospher's Stone"</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#00f;font-weight:bold">:</span><span style="color:#008000;font-weight:bold">ds-ng-1</span>.<span style="">ttl</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">---------------------------------------------------------------------------------------</span><span style="color:#bbb"> |
| </span></span></span></code></pre></div><h3 id="querying-a-specific-graph">Querying a specific graph</h3> |
| <p>If the application knows the name graph, it can directly ask a |
| query such as finding all the titles in a given graph |
| (<a href="sparql_data/q-ds-3.rq">q-ds-3.rq</a>):</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">PREFIX</span> <span style="color:#00f;font-weight:bold">dc</span>: <span style="color:#a0a000"><http://purl.org/dc/elements/1.1/></span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">PREFIX</span> : <span style="color:#a0a000"><.></span> |
| </span></span><span style="display:flex;"><span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">SELECT</span> <span style="color:#b8860b">?title</span> |
| </span></span><span style="display:flex;"><span>{ |
| </span></span><span style="display:flex;"><span> <span style="color:#a2f;font-weight:bold">GRAPH</span> :<span style="color:#008000;font-weight:bold">ds-ng-2.ttl</span> |
| </span></span><span style="display:flex;"><span> { <span style="color:#b8860b">?b</span> <span style="color:#00f;font-weight:bold">dc</span>:<span style="color:#008000;font-weight:bold">title</span> <span style="color:#b8860b">?title</span> } |
| </span></span><span style="display:flex;"><span>} |
| </span></span></code></pre></div><p>Results:</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="">---------------------------------------------</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="">title</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">=============================================</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Sorcerer's Stone"</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Chamber of Secrets"</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">---------------------------------------------</span><span style="color:#bbb"> |
| </span></span></span></code></pre></div><h3 id="querying-to-find-data-from-graphs-that-match-a-pattern">Querying to find data from graphs that match a pattern</h3> |
| <p>The name of the graphs to be queried can be determined with the |
| query itself. The same process for variables applies whether they |
| are part of a graph pattern or the <code>GRAPH</code> form. The query below |
| (<a href="sparql_data/q-ds-4.rq">q-ds-4.rq</a>) sets a condition on the variable used to |
| select named graphs, based on information in the default graph.</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">PREFIX</span> <span style="color:#00f;font-weight:bold">xsd</span>: <span style="color:#a0a000"><http://www.w3.org/2001/XMLSchema#></span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">PREFIX</span> <span style="color:#00f;font-weight:bold">dc</span>: <span style="color:#a0a000"><http://purl.org/dc/elements/1.1/></span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">PREFIX</span> : <span style="color:#a0a000"><.></span> |
| </span></span><span style="display:flex;"><span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">SELECT</span> <span style="color:#b8860b">?date</span> <span style="color:#b8860b">?title</span> |
| </span></span><span style="display:flex;"><span>{ |
| </span></span><span style="display:flex;"><span> <span style="color:#b8860b">?g</span> <span style="color:#00f;font-weight:bold">dc</span>:<span style="color:#008000;font-weight:bold">date</span> <span style="color:#b8860b">?date</span> . <span style="color:#a2f;font-weight:bold">FILTER</span> (<span style="color:#b8860b">?date</span> <span style="color:#666">></span> <span style="color:#b44">"2005-08-01T00:00:00Z"</span><span style="color:#666">^^</span><span style="color:#00f;font-weight:bold">xsd</span>:<span style="color:#008000;font-weight:bold">dateTime</span> ) |
| </span></span><span style="display:flex;"><span> <span style="color:#a2f;font-weight:bold">GRAPH</span> <span style="color:#b8860b">?g</span> |
| </span></span><span style="display:flex;"><span> { <span style="color:#b8860b">?b</span> <span style="color:#00f;font-weight:bold">dc</span>:<span style="color:#008000;font-weight:bold">title</span> <span style="color:#b8860b">?title</span> } |
| </span></span><span style="display:flex;"><span>} |
| </span></span></code></pre></div><p>The results of executing this query on the example dataset are the |
| titles in one of the graphs, the one with the date later than 1 |
| August 2005.</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="">-----------------------------------------------------------------------------------------</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="">date</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="">title</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">=========================================================================================</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"2005-09-22T05:53:05+01:00"</span><span style="color:#666">^^</span><span style="font-style:italic">xsd:dateTime</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Sorcerer's Stone"</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"2005-09-22T05:53:05+01:00"</span><span style="color:#666">^^</span><span style="font-style:italic">xsd:dateTime</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> </span><span style="color:#b44">"Harry Potter and the Chamber of Secrets"</span><span style="color:#bbb"> </span><span style="">|</span><span style="color:#bbb"> |
| </span></span></span><span style="display:flex;"><span><span style="color:#bbb"></span><span style="">-----------------------------------------------------------------------------------------</span><span style="color:#bbb"> |
| </span></span></span></code></pre></div><h2 id="describing-rdf-datasets---from-and-from-named">Describing RDF Datasets - <code>FROM</code> and <code>FROM NAMED</code></h2> |
| <p>A query execution can be given the dataset when the execution |
| object is built or it can be described in the query itself. When |
| the details are on the command line, a temporary dataset is created |
| but an application can create datasets and then use them in many |
| queries.</p> |
| <p>When described in the query, <code>FROM <</code><em><code>url</code></em><code>></code> is used to identify |
| the contents to be in the default graph. There can be more than one |
| <code>FROM</code> clause and the default graph is result of reading each file |
| into the default graph. It is the RDF merge of the individual |
| graphs.</p> |
| <p>Don’t be confused by the fact the default graph is described by one |
| or more URLs in <code>FROM</code> clauses. This is where the data is read |
| from, not the name of the graph. As several FROM clauses can be |
| given, the data can be read in from several places but none of them |
| become the graph name.</p> |
| <p><code>FROM NAMED <</code><em><code>url</code></em><code>></code> is used to identify a named graph. The |
| graph is given the name <em>url</em> and the data is read from that |
| location. Multiple <code>FROM NAMED</code> clauses cause multiple graphs to be |
| added to the dataset.</p> |
| <p>For example, the query to find all the triples in both default |
| graph and named graphs could be written as |
| (<a href="sparql_data/q-ds-5.rq">q-ds-5.rq</a>):</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">PREFIX</span> <span style="color:#00f;font-weight:bold">xsd</span>: <span style="color:#a0a000"><http://www.w3.org/2001/XMLSchema#></span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">PREFIX</span> <span style="color:#00f;font-weight:bold">dc</span>: <span style="color:#a0a000"><http://purl.org/dc/elements/1.1/></span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">PREFIX</span> : <span style="color:#a0a000"><.></span> |
| </span></span><span style="display:flex;"><span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">SELECT</span> <span style="color:#666">*</span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">FROM</span> <span style="color:#a0a000"><ds-dft.ttl></span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">FROM NAMED</span> <span style="color:#a0a000"><ds-ng-1.ttl></span> |
| </span></span><span style="display:flex;"><span><span style="color:#a2f;font-weight:bold">FROM NAMED</span> <span style="color:#a0a000"><ds-ng-2.ttl></span> |
| </span></span><span style="display:flex;"><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 style="color:#a2f;font-weight:bold">UNION</span> { <span style="color:#a2f;font-weight:bold">GRAPH</span> <span style="color:#b8860b">?g</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><p><a href="sparql_results.html">Next: results</a></p> |
| |
| </article> |
| |
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| <nav id="TableOfContents"> |
| <ul> |
| <li><a href="#querying-datasets">Querying datasets</a> |
| <ul> |
| <li><a href="#example-data">Example Data</a></li> |
| <li><a href="#accessing-the-dataset">Accessing the Dataset</a></li> |
| <li><a href="#querying-a-specific-graph">Querying a specific graph</a></li> |
| <li><a href="#querying-to-find-data-from-graphs-that-match-a-pattern">Querying to find data from graphs that match a pattern</a></li> |
| </ul> |
| </li> |
| <li><a href="#describing-rdf-datasets---from-and-from-named">Describing RDF Datasets - <code>FROM</code> and <code>FROM NAMED</code></a></li> |
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| </script> |
| |
| </body> |
| </html> |
