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             <h1 class="title">Functions in ARQ</h1>

 	<p>The regular expressions for fan:localname and afn:namespace were incorrect.
 SPARQL allows custom functions in expressions so that
 queries can be used on domain-specific data. SPARQL defines a
 function by URI (or prefixed name) in FILTER expressions.  ARQ
 provides a function library and supports application-provided
 functions.  Functions and property functions can be
 <a href="extension.html">registered or dynamically loaded</a>.</p>
 <p>Applications can also
 <a href="writing_functions.html">provide their own functions</a>.</p>
 <p>ARQ also provides an implementation the
 <a href="http://www.dotnetrdf.org/leviathan">Leviathan Function Library</a>.</p>
 <h3 id="xqueryxpath-functions-and-operators-supported">XQuery/XPath Functions and Operators supported</h3>
 <p>ARQ supports the scalar functions and operators from
 &ldquo;<a href="https://www.w3.org/TR/xpath-functions-3/">XQuery 1.0 and XPath 2.0 Functions and Operators v3.1</a>&quot;.</p>
 <p>Functions in involving sequences are not supported.</p>
 <p>See <a href="xsd-support.html">XSD Support</a> for details of datatypes and functions
 currently supported.  To check the exact current registrations, see
 <tt><a href="https://github.com/apache/jena/blob/main/jena-arq/src/main/java/org/apache/jena/sparql/function/StandardFunctions.java">function/StandardFunctions.java</a></tt>.</p>
 <p>See also the <a href="library-propfunc.html">property functions</a> library
 page.</p>
 <h3 id="function-library">Function Library</h3>
 <p>The prefix <code>afn</code> is <code>&lt;http://jena.apache.org/ARQ/function#&gt;</code>.
 (The old prefix of <code>&lt;http://jena.hpl.hp.com/ARQ/function#&gt;</code> continues to
 work. Applications are encouraged to switch.)</p>
 <p>Direct loading using a URI prefix of
 <code>&lt;java:org.apache.jena.sparql.function.library.&gt;</code> (note the final
 dot) is deprecated.</p>
 <p>The prefix <code>fn</code> is <code>&lt;http://www.w3.org/2005/xpath-functions#&gt;</code> (the
 XPath and XQuery function namespace).</p>
 <p>The prefix <code>math</code> is <code>&lt;http://www.w3.org/2005/xpath-functions/math#&gt;</code>.</p>
 <h3 id="custom-aggregates">Custom Aggregates</h3>
 <p>The prefix <code>agg:</code> is <code>&lt;http://jena.apache.org/ARQ/function/aggregate#&gt;</code>.</p>
 <p>The statistical aggregates are provided are:</p>
 <p><code>agg:stdev</code>, <code>agg:stdev_samp</code>, <code>agg:stdev_pop</code>,
 <code>agg:variance</code>, <code>agg:var_samp</code>, <code>agg:var_pop</code></p>
 <p>These are modelled after SQL aggregate functions <code>STDEV</code>, <code>STDEV_SAMP</code>, <code>STDEV_POP</code>,
 <code>VARIANCE</code>, <code>VAR_SAMP</code>, <code>VAR_POP</code>.</p>
 <p>These, as keywords, are available in ARQ&rsquo;s extended SPARQL (parse using <code>Syntax.syntaxARQ</code>).</p>
 <h3 id="additional-functions-provided-by-arq">Additional Functions Provided by ARQ</h3>
 <p>Most of these have equivalents, or near equivalents, in SPARQL or as an
 XQuery function and are to be preferred. These ARQ-specific versions remain
 for compatibility.</p>
 <p><strong>RDF Graph Functions</strong></p>
 <table>
 <thead>
 <tr>
 <th>Function name</th>
 <th>Description</th>
 <th>Alternative</th>
 </tr>
 </thead>
 <tbody>
 <tr>
 <td><code>afn:bnode(?x)</code></td>
 <td>Return the blank node label if ?x is a blank node.</td>
 <td><code>STR(?x)</code></td>
 </tr>
 <tr>
 <td><code>afn:localname(?x)</code></td>
 <td>The local name of ?x</td>
 <td><code>REPLACE(STR(?x), &quot;^(.*)(/|#)([^#/]*)$&quot;, &quot;$3&quot;)</code></td>
 </tr>
 <tr>
 <td><code>afn:namespace(?x)</code></td>
 <td>The namespace of ?x</td>
 <td><code>REPLACE(STR(?x), &quot;^(.*)(/|#)([^#/]*)$&quot;, &quot;$1&quot;)</code></td>
 </tr>
 </tbody>
 </table>
 <p>The prefix and local name of a IRI is based on splitting the IRI, not on any prefixes in the query or dataset.</p>
 <p><strong>String Functions</strong></p>
 <table>
 <thead>
 <tr>
 <th>Function name</th>
 <th>Description</th>
 <th>Alternative</th>
 </tr>
 </thead>
 <tbody>
 <tr>
 <td><code>afn:sprintf(format, v1, v2, ...)</code></td>
 <td>Make a string from the format string and the RDF terms.</td>
 <td></td>
 </tr>
 <tr>
 <td><code>afn:substr(string, startIndex [,endIndex])</code></td>
 <td>Substring, Java style using <em><code>startIndex</code></em> and <em><code>endIndex</code></em>.</td>
 <td></td>
 </tr>
 <tr>
 <td><code>afn:substring</code></td>
 <td>Synonym for afn:substr</td>
 <td></td>
 </tr>
 <tr>
 <td><code>afn:strjoin(sep, string ...)</code></td>
 <td>Concatenate string together, with a separator.</td>
 <td></td>
 </tr>
 <tr>
 <td><code>afn:sha1sum(resource)</code></td>
 <td>Calculate the SHA1 checksum of a literal or URI</td>
 <td><code>SHA1(STR(resource))</code></td>
 </tr>
 </tbody>
 </table>
 <p>Notes:</p>
 <ol>
 <li>Strings in
 &ldquo;<a href="http://www.w3.org/TR/xpath-functions-3/">XQuery 1.0 and XPath 2.0 Functions and Operators</a>&rdquo;
 start from character position one, unlike Java and C# where
 strings start from zero.</li>
 <li>The <code>fn:substring</code> operation takes an optional length, like C#
 but different from Java, where it is the <em>endIndex</em> of the first
 character after the substring.</li>
 <li><code>afn:substr</code> uses Java-style  <em><code>startIndex</code></em> and <em><code>endIndex</code></em>.</li>
 </ol>
 <p><strong>Mathematical Functions</strong></p>
 <table>
 <thead>
 <tr>
 <th>Function name</th>
 <th>Description</th>
 <th>Alternative</th>
 </tr>
 </thead>
 <tbody>
 <tr>
 <td><code>afn:min(num1, num2)</code></td>
 <td>Return the minimum of two numbers</td>
 <td><code>fn:min</code></td>
 </tr>
 <tr>
 <td><code>afn:max(num1, num2)</code></td>
 <td>Return the maximum of two numbers</td>
 <td><code>fn:max</code></td>
 </tr>
 <tr>
 <td><code>afn:pi()</code></td>
 <td>The value of pi, as an XSD double</td>
 <td><code>math:pi()</code></td>
 </tr>
 <tr>
 <td><code>afn:e()</code></td>
 <td>The value of e, as an XSD double</td>
 <td><code>math:exp(1)</code></td>
 </tr>
 <tr>
 <td><code>afn:sqrt(num)</code></td>
 <td>The square root of num</td>
 <td><code>math:sqrt</code></td>
 </tr>
 </tbody>
 </table>
 <p><strong>Miscellaneous Functions</strong></p>
 <table>
 <thead>
 <tr>
 <th>Function name</th>
 <th>Description</th>
 <th>Alternative</th>
 </tr>
 </thead>
 <tbody>
 <tr>
 <td><code>afn:now()</code></td>
 <td>Current time. Actually, the time the query started.</td>
 <td><code>NOW()</code></td>
 </tr>
 <tr>
 <td><code>afn:sha1sum(resource)</code></td>
 <td>Calculate the SHA1 checksum</td>
 <td><code>SHASUM</code></td>
 </tr>
 </tbody>
 </table>


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	</div>
	<h1 class="title">Functions in ARQ</h1>

	<p>The regular expressions for fan:localname and afn:namespace were incorrect.
	SPARQL allows custom functions in expressions so that
	queries can be used on domain-specific data. SPARQL defines a
	function by URI (or prefixed name) in FILTER expressions. ARQ
	provides a function library and supports application-provided
	functions. Functions and property functions can be
	<a href="extension.html">registered or dynamically loaded</a>.</p>
	<p>Applications can also
	<a href="writing_functions.html">provide their own functions</a>.</p>
	<p>ARQ also provides an implementation the
	<a href="http://www.dotnetrdf.org/leviathan">Leviathan Function Library</a>.</p>
	<h3 id="xqueryxpath-functions-and-operators-supported">XQuery/XPath Functions and Operators supported</h3>
	<p>ARQ supports the scalar functions and operators from
	“<a href="https://www.w3.org/TR/xpath-functions-3/">XQuery 1.0 and XPath 2.0 Functions and Operators v3.1</a>".</p>
	<p>Functions in involving sequences are not supported.</p>
	<p>See <a href="xsd-support.html">XSD Support</a> for details of datatypes and functions
	currently supported. To check the exact current registrations, see
	<tt><a href="https://github.com/apache/jena/blob/main/jena-arq/src/main/java/org/apache/jena/sparql/function/StandardFunctions.java">function/StandardFunctions.java</a></tt>.</p>
	<p>See also the <a href="library-propfunc.html">property functions</a> library
	page.</p>
	<h3 id="function-library">Function Library</h3>
	<p>The prefix <code>afn</code> is <code><http://jena.apache.org/ARQ/function#></code>.
	(The old prefix of <code><http://jena.hpl.hp.com/ARQ/function#></code> continues to
	work. Applications are encouraged to switch.)</p>
	<p>Direct loading using a URI prefix of
	<code><java:org.apache.jena.sparql.function.library.></code> (note the final
	dot) is deprecated.</p>
	<p>The prefix <code>fn</code> is <code><http://www.w3.org/2005/xpath-functions#></code> (the
	XPath and XQuery function namespace).</p>
	<p>The prefix <code>math</code> is <code><http://www.w3.org/2005/xpath-functions/math#></code>.</p>
	<h3 id="custom-aggregates">Custom Aggregates</h3>
	<p>The prefix <code>agg:</code> is <code><http://jena.apache.org/ARQ/function/aggregate#></code>.</p>
	<p>The statistical aggregates are provided are:</p>
	<p><code>agg:stdev</code>, <code>agg:stdev_samp</code>, <code>agg:stdev_pop</code>,
	<code>agg:variance</code>, <code>agg:var_samp</code>, <code>agg:var_pop</code></p>
	<p>These are modelled after SQL aggregate functions <code>STDEV</code>, <code>STDEV_SAMP</code>, <code>STDEV_POP</code>,
	<code>VARIANCE</code>, <code>VAR_SAMP</code>, <code>VAR_POP</code>.</p>
	<p>These, as keywords, are available in ARQ’s extended SPARQL (parse using <code>Syntax.syntaxARQ</code>).</p>
	<h3 id="additional-functions-provided-by-arq">Additional Functions Provided by ARQ</h3>
	<p>Most of these have equivalents, or near equivalents, in SPARQL or as an
	XQuery function and are to be preferred. These ARQ-specific versions remain
	for compatibility.</p>
	<p><strong>RDF Graph Functions</strong></p>
	<table>
	<thead>
	<tr>
	<th>Function name</th>
	<th>Description</th>
	<th>Alternative</th>
	</tr>
	</thead>
	<tbody>
	<tr>
	<td><code>afn:bnode(?x)</code></td>
	<td>Return the blank node label if ?x is a blank node.</td>
	<td><code>STR(?x)</code></td>
	</tr>
	<tr>
	<td><code>afn:localname(?x)</code></td>
	<td>The local name of ?x</td>
	<td><code>REPLACE(STR(?x), "^(.)(/\|#)([^#/])$", "$3")</code></td>
	</tr>
	<tr>
	<td><code>afn:namespace(?x)</code></td>
	<td>The namespace of ?x</td>
	<td><code>REPLACE(STR(?x), "^(.)(/\|#)([^#/])$", "$1")</code></td>
	</tr>
	</tbody>
	</table>
	<p>The prefix and local name of a IRI is based on splitting the IRI, not on any prefixes in the query or dataset.</p>
	<p><strong>String Functions</strong></p>
	<table>
	<thead>
	<tr>
	<th>Function name</th>
	<th>Description</th>
	<th>Alternative</th>
	</tr>
	</thead>
	<tbody>
	<tr>
	<td><code>afn:sprintf(format, v1, v2, ...)</code></td>
	<td>Make a string from the format string and the RDF terms.</td>
	<td></td>
	</tr>
	<tr>
	<td><code>afn:substr(string, startIndex [,endIndex])</code></td>
	<td>Substring, Java style using <em><code>startIndex</code></em> and <em><code>endIndex</code></em>.</td>
	<td></td>
	</tr>
	<tr>
	<td><code>afn:substring</code></td>
	<td>Synonym for afn:substr</td>
	<td></td>
	</tr>
	<tr>
	<td><code>afn:strjoin(sep, string ...)</code></td>
	<td>Concatenate string together, with a separator.</td>
	<td></td>
	</tr>
	<tr>
	<td><code>afn:sha1sum(resource)</code></td>
	<td>Calculate the SHA1 checksum of a literal or URI</td>
	<td><code>SHA1(STR(resource))</code></td>
	</tr>
	</tbody>
	</table>
	<p>Notes:</p>
	<ol>
	<li>Strings in
	“<a href="http://www.w3.org/TR/xpath-functions-3/">XQuery 1.0 and XPath 2.0 Functions and Operators</a>”
	start from character position one, unlike Java and C# where
	strings start from zero.</li>
	<li>The <code>fn:substring</code> operation takes an optional length, like C#
	but different from Java, where it is the <em>endIndex</em> of the first
	character after the substring.</li>
	<li><code>afn:substr</code> uses Java-style <em><code>startIndex</code></em> and <em><code>endIndex</code></em>.</li>
	</ol>
	<p><strong>Mathematical Functions</strong></p>
	<table>
	<thead>
	<tr>
	<th>Function name</th>
	<th>Description</th>
	<th>Alternative</th>
	</tr>
	</thead>
	<tbody>
	<tr>
	<td><code>afn:min(num1, num2)</code></td>
	<td>Return the minimum of two numbers</td>
	<td><code>fn:min</code></td>
	</tr>
	<tr>
	<td><code>afn:max(num1, num2)</code></td>
	<td>Return the maximum of two numbers</td>
	<td><code>fn:max</code></td>
	</tr>
	<tr>
	<td><code>afn:pi()</code></td>
	<td>The value of pi, as an XSD double</td>
	<td><code>math:pi()</code></td>
	</tr>
	<tr>
	<td><code>afn:e()</code></td>
	<td>The value of e, as an XSD double</td>
	<td><code>math:exp(1)</code></td>
	</tr>
	<tr>
	<td><code>afn:sqrt(num)</code></td>
	<td>The square root of num</td>
	<td><code>math:sqrt</code></td>
	</tr>
	</tbody>
	</table>
	<p><strong>Miscellaneous Functions</strong></p>
	<table>
	<thead>
	<tr>
	<th>Function name</th>
	<th>Description</th>
	<th>Alternative</th>
	</tr>
	</thead>
	<tbody>
	<tr>
	<td><code>afn:now()</code></td>
	<td>Current time. Actually, the time the query started.</td>
	<td><code>NOW()</code></td>
	</tr>
	<tr>
	<td><code>afn:sha1sum(resource)</code></td>
	<td>Calculate the SHA1 checksum</td>
	<td><code>SHASUM</code></td>
	</tr>
	</tbody>
	</table>


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