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<div class="refentry" lang="en">
<a name="redland-query"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="redland-query.top_of_page"></a>Querying</span></h2>
<p>Querying — RDF query languages and execution.</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsynopsisdiv">
<a name="redland-query.synopsis"></a><h2>Synopsis</h2>
<pre class="synopsis">
typedef <a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a>;
typedef <a class="link" href="redland-query.html#librdf-query-factory" title="librdf_query_factory">librdf_query_factory</a>;
void <a class="link" href="redland-query.html#librdf-query-register-factory" title="librdf_query_register_factory ()">librdf_query_register_factory</a> (<a class="link" href="redland-world.html#librdf-world" title="librdf_world">librdf_world</a> *world,
const char *name,
unsigned char *uri_string,
void (factorylibrdf_query_factory*) ());
<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a>* <a class="link" href="redland-query.html#librdf-new-query" title="librdf_new_query ()">librdf_new_query</a> (<a class="link" href="redland-world.html#librdf-world" title="librdf_world">librdf_world</a> *world,
const char *name,
<a class="link" href="redland-uri.html#librdf-uri" title="librdf_uri">librdf_uri</a> *uri,
unsigned char *query_string,
<a class="link" href="redland-uri.html#librdf-uri" title="librdf_uri">librdf_uri</a> *base_uri);
<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a>* <a class="link" href="redland-query.html#librdf-new-query-from-query" title="librdf_new_query_from_query ()">librdf_new_query_from_query</a> (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *old_query);
<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a>* <a class="link" href="redland-query.html#librdf-new-query-from-factory" title="librdf_new_query_from_factory ()">librdf_new_query_from_factory</a> (<a class="link" href="redland-world.html#librdf-world" title="librdf_world">librdf_world</a> *world,
<a class="link" href="redland-query.html#librdf-query-factory" title="librdf_query_factory">librdf_query_factory</a> *factory,
const char *name,
<a class="link" href="redland-uri.html#librdf-uri" title="librdf_uri">librdf_uri</a> *uri,
unsigned char *query_string,
<a class="link" href="redland-uri.html#librdf-uri" title="librdf_uri">librdf_uri</a> *base_uri);
void <a class="link" href="redland-query.html#librdf-free-query" title="librdf_free_query ()">librdf_free_query</a> (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query);
<a class="link" href="redland-query-results.html#librdf-query-results" title="librdf_query_results">librdf_query_results</a>* <a class="link" href="redland-query.html#librdf-query-execute" title="librdf_query_execute ()">librdf_query_execute</a> (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query,
<a class="link" href="redland-model.html#librdf-model" title="librdf_model">librdf_model</a> *model);
int <a class="link" href="redland-query.html#librdf-query-get-limit" title="librdf_query_get_limit ()">librdf_query_get_limit</a> (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query);
int <a class="link" href="redland-query.html#librdf-query-set-limit" title="librdf_query_set_limit ()">librdf_query_set_limit</a> (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query,
int limit);
int <a class="link" href="redland-query.html#librdf-query-get-offset" title="librdf_query_get_offset ()">librdf_query_get_offset</a> (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query);
int <a class="link" href="redland-query.html#librdf-query-set-offset" title="librdf_query_set_offset ()">librdf_query_set_offset</a> (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query,
int offset);
</pre>
</div>
<div class="refsect1" lang="en">
<a name="redland-query.description"></a><h2>Description</h2>
<p>
Provides classes to create query objects and to execute them over
an RDF graph (<a class="link" href="redland-model.html#librdf-model" title="librdf_model"><span class="type">librdf_model</span></a>) returning a <a class="link" href="redland-query-results.html#librdf-query-results" title="librdf_query_results"><span class="type">librdf_query_results</span></a>
Query result limits and offsets can be set.
</p>
</div>
<div class="refsect1" lang="en">
<a name="redland-query.details"></a><h2>Details</h2>
<div class="refsect2" lang="en">
<a name="librdf-query"></a><h3>librdf_query</h3>
<pre class="programlisting">typedef struct librdf_query_s librdf_query;
</pre>
<p>
Redland query class.</p>
<p>
</p>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="librdf-query-factory"></a><h3>librdf_query_factory</h3>
<pre class="programlisting">typedef struct librdf_query_factory_s librdf_query_factory;
</pre>
<p>
Redland query factory class.</p>
<p>
</p>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="librdf-query-register-factory"></a><h3>librdf_query_register_factory ()</h3>
<pre class="programlisting">void librdf_query_register_factory (<a class="link" href="redland-world.html#librdf-world" title="librdf_world">librdf_world</a> *world,
const char *name,
unsigned char *uri_string,
void (factorylibrdf_query_factory*) ());</pre>
<p>
Register a query factory.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>world</code></em> :</span></p></td>
<td> redland world object
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>name</code></em> :</span></p></td>
<td> the query language name
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>uri_string</code></em> :</span></p></td>
<td> the query language URI string (or NULL if none)
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>factory</code></em> :</span></p></td>
<td> pointer to function to call to register the factory
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="librdf-new-query"></a><h3>librdf_new_query ()</h3>
<pre class="programlisting"><a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a>* librdf_new_query (<a class="link" href="redland-world.html#librdf-world" title="librdf_world">librdf_world</a> *world,
const char *name,
<a class="link" href="redland-uri.html#librdf-uri" title="librdf_uri">librdf_uri</a> *uri,
unsigned char *query_string,
<a class="link" href="redland-uri.html#librdf-uri" title="librdf_uri">librdf_uri</a> *base_uri);</pre>
<p>
Constructor - create a new <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> object.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>world</code></em> :</span></p></td>
<td> redland world object
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>name</code></em> :</span></p></td>
<td> the name identifying the query language
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>uri</code></em> :</span></p></td>
<td> the URI identifying the query language (or NULL)
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>query_string</code></em> :</span></p></td>
<td> the query string
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>base_uri</code></em> :</span></p></td>
<td> the base URI of the query string (or NULL)
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> a new <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> object or NULL on failure
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="librdf-new-query-from-query"></a><h3>librdf_new_query_from_query ()</h3>
<pre class="programlisting"><a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a>* librdf_new_query_from_query (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *old_query);</pre>
<p>
Should create a new query in the same context as the existing one
as appropriate.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>old_query</code></em> :</span></p></td>
<td> the existing query <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> to use
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> a new <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> object or NULL on failure
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="librdf-new-query-from-factory"></a><h3>librdf_new_query_from_factory ()</h3>
<pre class="programlisting"><a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a>* librdf_new_query_from_factory (<a class="link" href="redland-world.html#librdf-world" title="librdf_world">librdf_world</a> *world,
<a class="link" href="redland-query.html#librdf-query-factory" title="librdf_query_factory">librdf_query_factory</a> *factory,
const char *name,
<a class="link" href="redland-uri.html#librdf-uri" title="librdf_uri">librdf_uri</a> *uri,
unsigned char *query_string,
<a class="link" href="redland-uri.html#librdf-uri" title="librdf_uri">librdf_uri</a> *base_uri);</pre>
<p>
Constructor - create a new <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> object.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>world</code></em> :</span></p></td>
<td> redland world object
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>factory</code></em> :</span></p></td>
<td> the factory to use to construct the query
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>name</code></em> :</span></p></td>
<td> query language name
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>uri</code></em> :</span></p></td>
<td> query language URI (or NULL)
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>query_string</code></em> :</span></p></td>
<td> the query string
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>base_uri</code></em> :</span></p></td>
<td> base URI of the query string (or NULL)
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> a new <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> object or NULL on failure
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="librdf-free-query"></a><h3>librdf_free_query ()</h3>
<pre class="programlisting">void librdf_free_query (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query);</pre>
<p>
Destructor - destroy a <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> object.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td><p><span class="term"><em class="parameter"><code>query</code></em> :</span></p></td>
<td> <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> object
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="librdf-query-execute"></a><h3>librdf_query_execute ()</h3>
<pre class="programlisting"><a class="link" href="redland-query-results.html#librdf-query-results" title="librdf_query_results">librdf_query_results</a>* librdf_query_execute (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query,
<a class="link" href="redland-model.html#librdf-model" title="librdf_model">librdf_model</a> *model);</pre>
<p>
Run the query on a model.
</p>
<p>
Runs the query against the (previously registered) model
and returns a <a class="link" href="redland-query-results.html#librdf-query-results" title="librdf_query_results"><span class="type">librdf_query_results</span></a> for the result objects.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>query</code></em> :</span></p></td>
<td> <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> object
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>model</code></em> :</span></p></td>
<td> model to operate query on
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> <a class="link" href="redland-query-results.html#librdf-query-results" title="librdf_query_results"><span class="type">librdf_query_results</span></a> or NULL on failure
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="librdf-query-get-limit"></a><h3>librdf_query_get_limit ()</h3>
<pre class="programlisting">int librdf_query_get_limit (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query);</pre>
<p>
Get the query-specified limit on results.
</p>
<p>
This is the limit given in the query on the number of results allowed.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>query</code></em> :</span></p></td>
<td> <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> query object
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> integer >=0 if a limit is given, otherwise <0
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="librdf-query-set-limit"></a><h3>librdf_query_set_limit ()</h3>
<pre class="programlisting">int librdf_query_set_limit (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query,
int limit);</pre>
<p>
Set the query-specified limit on results.
</p>
<p>
This is the limit given in the query on the number of results allowed.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>query</code></em> :</span></p></td>
<td> <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> query object
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>limit</code></em> :</span></p></td>
<td> the limit on results, >=0 to set a limit, <0 to have no limit
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> non-0 on failure
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="librdf-query-get-offset"></a><h3>librdf_query_get_offset ()</h3>
<pre class="programlisting">int librdf_query_get_offset (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query);</pre>
<p>
Get the query-specified offset on results.
</p>
<p>
This is the offset given in the query on the number of results allowed.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>query</code></em> :</span></p></td>
<td> <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> query object
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> integer >=0 if a offset is given, otherwise <0
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="librdf-query-set-offset"></a><h3>librdf_query_set_offset ()</h3>
<pre class="programlisting">int librdf_query_set_offset (<a class="link" href="redland-query.html#librdf-query" title="librdf_query">librdf_query</a> *query,
int offset);</pre>
<p>
Set the query-specified offset on results.
</p>
<p>
This is the offset given in the query on the number of results allowed.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>query</code></em> :</span></p></td>
<td> <a class="link" href="redland-query.html#librdf-query" title="librdf_query"><span class="type">librdf_query</span></a> query object
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>offset</code></em> :</span></p></td>
<td> offset for results, >=0 to set an offset, <0 to have no offset
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td> non-0 on failure
</td>
</tr>
</tbody>
</table></div>
</div>
</div>
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