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             <h1 class="title">ARQ - JavaScript SPARQL Functions</h1>

 	<p>ARQ supports (Jena v3.7.0 onwards) writing
 <a href="https://www.w3.org/TR/sparql11-query/#extensionFunctions">custom SPARQL functions</a>
 in JavaScript. These functions can be used in FILTERs and for calculating
 values to assign with AS in BIND and SELECT expressions.</p>
 <p>XSD datatypes for strings, numbers and booleans are converted to the
 native JavaScript datatypes. RDFterms that do not fit easily into
 JavaScript datatypes are handled with a object class <code>NV</code>.</p>
 <h2 id="loading-javascript-functions">Loading JavaScript functions</h2>
 <p>JavaScript is loaded from an external file using the context setting
 &ldquo;<a href="http://jena.apache.org/ARQ#js-library%22">http://jena.apache.org/ARQ#js-library&quot;</a>. This can be written as
 <code>arq:js-library</code> for commands and Fuseki configuration files.</p>
 <p>Example:</p>
 <pre><code>sparql --set arq:js-library=SomeFile.js --data ... --query ...
 </code></pre>
 <p>will execute on the data with the JavaScript functions from file
 &ldquo;SomeFile.js&rdquo; available.</p>
 <p>JavScript functions can also be set from a string directly from within Java using constant
 <code>ARQ.symJavaScriptFunctions</code> (&ldquo;<a href="http://jena.apache.org/ARQ#js-functions%22)">http://jena.apache.org/ARQ#js-functions&quot;)</a>.</p>
 <h2 id="using-javascript-functions">Using JavaScript functions</h2>
 <p>SPARQL functions implemented in JavaScript are automatically called when a
 URI starting &ldquo;<a href="http://jena.apache.org/ARQ/jsFunction#%22">http://jena.apache.org/ARQ/jsFunction#&quot;</a> used.</p>
 <p>This can conveniently be abbreviated by:</p>
 <pre><code>PREFIX js: &lt;http://jena.apache.org/ARQ/jsFunction#&gt;
 </code></pre>
 <h3 id="arguments-and-function-results">Arguments and Function Results</h3>
 <p><code>xsd:string</code> (a string with no language tag), any XSD numbers (integer,
 decimal, float, double and all the derived types) and <code>xsd:boolean</code> are
 converted to JavaScript string, number and boolean respectively.</p>
 <p>SPARQL functions must return a value. When a function returns a value,
 it can be one of these JavaScript native datatypes, in which case the
 reverse conversion is applied back to XSD datatypes.  For numbers, the
 conversion is back to <code>xsd:integer</code> (if it has no fractional part) or
 <code>xsd:double</code>.</p>
 <p>The JavaScript function can also create <code>NodeValue</code> (or <code>NV</code>) objects
 for other datatypes by calling Java from within the JavaScript script
 engine of the Java runtime.</p>
 <p>URIs are passed as <code>NV</code> object and are available in JavaScript as a string.</p>
 <p>The class <code>NV</code> is used for all other RDF terms.</p>
 <p>Returning JavaScript <code>null</code> is the error indicator and a SPARQL
 expression error (<code>ExprEvalException</code>) is raised, like any other
 expression error in SPARQL. That, in turn, will cause the whole
 expression the function is part of to evaluate to an error (unless
 a special form like <code>COALESCE</code> is used). In a <code>FILTER</code> that typically
 makes the filter evaluate to &ldquo;false&rdquo;.</p>
 <h2 id="example">Example</h2>
 <p>Suppose &ldquo;functions.js&rdquo; contains code to camel case words in a string.
 For example, &ldquo;some words to process &quot; becomes &ldquo;someWordsToProcess&rdquo;.</p>
 <pre><code>// CamelCase a string
 // Words to be combined are separated by a space in the string.

 function toCamelCase(str) {
     return str.split(' ')
     .map(cc)
     .join('');
 }

 function ucFirst(word)    {
     return word.charAt(0).toUpperCase() + word.slice(1).toLowerCase();
 }

 function lcFirst(word)    {
     return word.toLowerCase();
 }

 function cc(word,index)   {
     return (index == 0) ? lcFirst(word) : ucFirst(word);
 }
 </code></pre>
 <p>and the query <code>Q.rq</code></p>
 <pre><code>PREFIX js: &lt;http://jena.apache.org/ARQ/jsFunction#&gt;

 SELECT ?input (js:toCamelCase(?input) AS ?X)
 {
     VALUES ?input { &quot;some woRDs to PROCESS&quot; }
 }
 </code></pre>
 <p>which can be executed with:</p>
 <pre><code>sparql --set arq:js-library=functions.js --query Q.rq
 </code></pre>
 <p>and it results in:</p>
 <pre><code>--------------------------------------------------
 | input                   | X                    |
 ==================================================
 | &quot;some woRDs to PROCESS&quot; | &quot;someWordsToProcess&quot; |
 --------------------------------------------------
 </code></pre>
 <h2 id="use-with-fuseki">Use with Fuseki</h2>
 <p>The context setting can be provided on the command line starting the
 server, for example:</p>
 <pre><code>fuseki --set arq:js-library=functions.js --mem /ds
 </code></pre>
 <p>or it can be specified in the server configuration file <code>config.ttl</code>:</p>
 <pre><code>PREFIX :        &lt;#&gt;
 PREFIX fuseki:  &lt;http://jena.apache.org/fuseki#&gt;
 PREFIX rdf:     &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt;
 PREFIX rdfs:    &lt;http://www.w3.org/2000/01/rdf-schema#&gt;
 PREFIX ja:      &lt;http://jena.hpl.hp.com/2005/11/Assembler#&gt;

 [] rdf:type fuseki:Server ;
     # Set the server-wide context
     ja:context [
          ja:cxtName &quot;arq:js-library&quot; ;
          ja:cxtValue &quot;/filepath/functions.js&quot;
     ] ;
 .

 &lt;#service&gt; rdf:type fuseki:Service;
     rdfs:label                   &quot;Dataset&quot;;
     fuseki:name                  &quot;ds&quot;;
     fuseki:serviceQuery          &quot;sparql&quot;;
     fuseki:dataset &lt;#dataset&gt; ;
     .

 &lt;#dataset&gt; rdf:type ja:DatasetTxnMem;
     ja:data &lt;file:D.trig&gt;;
 .
 </code></pre>
 <p>and used as:</p>
 <pre><code>fuseki --conf config.ttl
 </code></pre>


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	</div>
	<h1 class="title">ARQ - JavaScript SPARQL Functions</h1>

	<p>ARQ supports (Jena v3.7.0 onwards) writing
	<a href="https://www.w3.org/TR/sparql11-query/#extensionFunctions">custom SPARQL functions</a>
	in JavaScript. These functions can be used in FILTERs and for calculating
	values to assign with AS in BIND and SELECT expressions.</p>
	<p>XSD datatypes for strings, numbers and booleans are converted to the
	native JavaScript datatypes. RDFterms that do not fit easily into
	JavaScript datatypes are handled with a object class <code>NV</code>.</p>
	<h2 id="loading-javascript-functions">Loading JavaScript functions</h2>
	<p>JavaScript is loaded from an external file using the context setting
	“<a href="http://jena.apache.org/ARQ#js-library%22">http://jena.apache.org/ARQ#js-library"</a>. This can be written as
	<code>arq:js-library</code> for commands and Fuseki configuration files.</p>
	<p>Example:</p>
	<pre><code>sparql --set arq:js-library=SomeFile.js --data ... --query ...
	</code></pre>
	<p>will execute on the data with the JavaScript functions from file
	“SomeFile.js” available.</p>
	<p>JavScript functions can also be set from a string directly from within Java using constant
	<code>ARQ.symJavaScriptFunctions</code> (“<a href="http://jena.apache.org/ARQ#js-functions%22)">http://jena.apache.org/ARQ#js-functions")</a>.</p>
	<h2 id="using-javascript-functions">Using JavaScript functions</h2>
	<p>SPARQL functions implemented in JavaScript are automatically called when a
	URI starting “<a href="http://jena.apache.org/ARQ/jsFunction#%22">http://jena.apache.org/ARQ/jsFunction#"</a> used.</p>
	<p>This can conveniently be abbreviated by:</p>
	<pre><code>PREFIX js: <http://jena.apache.org/ARQ/jsFunction#>
	</code></pre>
	<h3 id="arguments-and-function-results">Arguments and Function Results</h3>
	<p><code>xsd:string</code> (a string with no language tag), any XSD numbers (integer,
	decimal, float, double and all the derived types) and <code>xsd:boolean</code> are
	converted to JavaScript string, number and boolean respectively.</p>
	<p>SPARQL functions must return a value. When a function returns a value,
	it can be one of these JavaScript native datatypes, in which case the
	reverse conversion is applied back to XSD datatypes. For numbers, the
	conversion is back to <code>xsd:integer</code> (if it has no fractional part) or
	<code>xsd:double</code>.</p>
	<p>The JavaScript function can also create <code>NodeValue</code> (or <code>NV</code>) objects
	for other datatypes by calling Java from within the JavaScript script
	engine of the Java runtime.</p>
	<p>URIs are passed as <code>NV</code> object and are available in JavaScript as a string.</p>
	<p>The class <code>NV</code> is used for all other RDF terms.</p>
	<p>Returning JavaScript <code>null</code> is the error indicator and a SPARQL
	expression error (<code>ExprEvalException</code>) is raised, like any other
	expression error in SPARQL. That, in turn, will cause the whole
	expression the function is part of to evaluate to an error (unless
	a special form like <code>COALESCE</code> is used). In a <code>FILTER</code> that typically
	makes the filter evaluate to “false”.</p>
	<h2 id="example">Example</h2>
	<p>Suppose “functions.js” contains code to camel case words in a string.
	For example, “some words to process " becomes “someWordsToProcess”.</p>
	<pre><code>// CamelCase a string
	// Words to be combined are separated by a space in the string.

	function toCamelCase(str) {
	return str.split(' ')
	.map(cc)
	.join('');
	}

	function ucFirst(word) {
	return word.charAt(0).toUpperCase() + word.slice(1).toLowerCase();
	}

	function lcFirst(word) {
	return word.toLowerCase();
	}

	function cc(word,index) {
	return (index == 0) ? lcFirst(word) : ucFirst(word);
	}
	</code></pre>
	<p>and the query <code>Q.rq</code></p>
	<pre><code>PREFIX js: <http://jena.apache.org/ARQ/jsFunction#>

	SELECT ?input (js:toCamelCase(?input) AS ?X)
	{
	VALUES ?input { "some woRDs to PROCESS" }
	}
	</code></pre>
	<p>which can be executed with:</p>
	<pre><code>sparql --set arq:js-library=functions.js --query Q.rq
	</code></pre>
	<p>and it results in:</p>
	<pre><code>--------------------------------------------------
	\| input \| X \|
	==================================================
	\| "some woRDs to PROCESS" \| "someWordsToProcess" \|
	--------------------------------------------------
	</code></pre>
	<h2 id="use-with-fuseki">Use with Fuseki</h2>
	<p>The context setting can be provided on the command line starting the
	server, for example:</p>
	<pre><code>fuseki --set arq:js-library=functions.js --mem /ds
	</code></pre>
	<p>or it can be specified in the server configuration file <code>config.ttl</code>:</p>
	<pre><code>PREFIX : <#>
	PREFIX fuseki: <http://jena.apache.org/fuseki#>
	PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
	PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
	PREFIX ja: <http://jena.hpl.hp.com/2005/11/Assembler#>

	[] rdf:type fuseki:Server ;
	# Set the server-wide context
	ja:context [
	ja:cxtName "arq:js-library" ;
	ja:cxtValue "/filepath/functions.js"
	] ;
	.

	<#service> rdf:type fuseki:Service;
	rdfs:label "Dataset";
	fuseki:name "ds";
	fuseki:serviceQuery "sparql";
	fuseki:dataset <#dataset> ;
	.

	<#dataset> rdf:type ja:DatasetTxnMem;
	ja:data <file:D.trig>;
	.
	</code></pre>
	<p>and used as:</p>
	<pre><code>fuseki --conf config.ttl
	</code></pre>


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