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<table class="confluenceTable"><tbody>
<tr>
<td class="confluenceTd"><p> Module: </p></td>
<td class="confluenceTd"><p> CQL Parser </p></td>
</tr>
<tr>
<td class="confluenceTd"><p> Module Maintainer: </p></td>
<td class="confluenceTd"><p> <a class="confluence-link confluence-userlink" data-username="mauricio.pazos" href="/display/~mauricio.pazos" data-linked-resource-id="67284" data-linked-resource-type="userinfo" username="mauricio.pazos" data-linked-resource-default-alias="Mauricio Pazos" data-base-url="http://docs.codehaus.org">Mauricio Pazos</a> </p></td>
</tr>
<tr>
<td class="confluenceTd"><p> Email Help: </p></td>
<td class="confluenceTd"><p> Geotools-gt2-users@lists.sourceforge.net </p></td>
</tr>
<tr>
<td class="confluenceTd"><p> Volunteer: </p></td>
<td class="confluenceTd"><p> geotools-devel@lists.sourceforge.net </p></td>
</tr>
<tr>
<td class="confluenceTd"><p> Status: </p></td>
<td class="confluenceTd"><p> <table class="wysiwyg-macro" data-macro-name="excerpt" data-macro-parameters="atlassian-macro-output-type=INLINE" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2V4Y2VycHQ6YXRsYXNzaWFuLW1hY3JvLW91dHB1dC10eXBlPUlOTElORX0&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="RICH_TEXT"><tr><td class="wysiwyg-macro-body"><p> <img class="emoticon emoticon-yellow-star" data-emoticon-name="yellow-star" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/star_yellow.png" alt="(star)" title="(star)" /> <img class="emoticon emoticon-yellow-star" data-emoticon-name="yellow-star" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/star_yellow.png" alt="(star)" title="(star)" /> <img class="emoticon emoticon-yellow-star" data-emoticon-name="yellow-star" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/star_yellow.png" alt="(star)" title="(star)" /> <img class="emoticon emoticon-yellow-star" data-emoticon-name="yellow-star" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/star_yellow.png" alt="(star)" title="(star)" /> <img class="emoticon emoticon-yellow-star" data-emoticon-name="yellow-star" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/star_yellow.png" alt="(star)" title="(star)" /> </p></td></tr></table> </p></td>
</tr>
<tr>
<td class="confluenceTd"><p> Model  </p></td>
<td class="confluenceTd"><p> <a class="confluence-link" href="/display/GEOTOOLS/CQL+Parser+Design" data-linked-resource-id="67669" data-linked-resource-type="page" data-linked-resource-default-alias="CQL Parser Design" data-base-url="http://docs.codehaus.org">CQL Parser Design</a>; <a class="confluence-link" href="/display/GEOTOOLS/ECQL+Parser+Design" data-linked-resource-id="110493908" data-linked-resource-type="page" data-linked-resource-default-alias="ECQL Parser Design" data-base-url="http://docs.codehaus.org">ECQL Parser Design</a> </p></td>
</tr>
<tr>
<td class="confluenceTd"><p> User doc <br class="atl-forced-newline" /> </p></td>
<td class="confluenceTd"><p> <a class="confluence-link unresolved" data-content-title="14 CQL" data-space-key="GEOTDOC" data-linked-resource-default-alias="14 CQL" href="#">14 CQL</a> </p></td>
</tr>
</tbody></table>

<img class="editor-inline-macro" src="/plugins/servlet/confluence/placeholder/macro?definition=e3RvY30&amp;locale=en_GB&amp;version=2" data-macro-name="toc">
<h1>Gold Star Quality Assurance Check:</h1>

<p><img class="emoticon emoticon-yellow-star" data-emoticon-name="yellow-star" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/star_yellow.png" alt="(star)" title="(star)" /> IP Check: need to ensure all headers are in place<br />
<img class="emoticon emoticon-yellow-star" data-emoticon-name="yellow-star" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/star_yellow.png" alt="(star)" title="(star)" /> Releasable: no blocking issues<br />
<img class="emoticon emoticon-yellow-star" data-emoticon-name="yellow-star" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/star_yellow.png" alt="(star)" title="(star)" /> Quality Assurance: 84.9% test coverage reported by clover<br />
<img class="emoticon emoticon-yellow-star" data-emoticon-name="yellow-star" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/star_yellow.png" alt="(star)" title="(star)" /> Stability: based on reviewed GeoAPI Filter interfaces and reviewed CSW 2.0.1 BNF for CQL<br />
<img class="emoticon emoticon-yellow-star" data-emoticon-name="yellow-star" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/star_yellow.png" alt="(star)" title="(star)" /> <a class="confluence-link unresolved" data-content-title="14 CQL" data-space-key="GEOTDOC" data-linked-resource-default-alias="14 CQL" href="#">user</a> and design docs. Module maintainer does watches user list, answers email.</p>

<h1>Target</h1>

<p>A module dedicated to fully support the OGC Common Query Language, version 2.0.1, as a query predicate language inside GeoTools.</p>

<h1>Motivation</h1>

<p><a href="http://www.axios.es">Axios</a> has developed, for the <a href="http://b5m.gipuzkoa.net">Gipuzkoa Provincial Council</a>, <strong>Mobility and Land Planning Department</strong>, an implementation of the OGC Catalog Service for Web 2.0.1 specification, based on GeoAPI medatada interfaces and Geotools implementation to support the ISO-19115/19139 profile.</p>

<p>The <a href="http://portal.opengeospatial.org/files/?artifact_id=5929&amp;version=2">CSW specification</a>, in section 6.2.2 defines the complete BNF for a constraint language to use as query predicates in a CSW implementation, named <strong>OGC Common Query Language</strong>, CQL for short.</p>

<p>As the CSW implementation worked on useing exclusively <code>org.opengis.filter.Filter</code>, it was needed a converter from an input query, in <strong>CQL</strong> format, to an equivalent predicate in the form of a <strong>Filter</strong> object.</p>

<h1>Target Audience</h1>

<p>By being part of the GeoTools library, this little module would just allow for any client code to easily construct a filter using a more human friendly predicate language.</p>

<p>In particular, the GeoServer community is currently willing to use it to add friendly filtering capabilities in WMS GetMap requests, and I guess it could be used in WFS GetFeature too.</p>

<p>An example usage would be:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
http://server/geoserver/ows?service=WMS&amp;request=GetMap&amp;...&amp;CONSTRAINTLANGUAGE=CQL_TEXT&amp;CONSTRAINT="the_geom bbox(0, 0, 180, 90, 'EPSG:4326')"
</pre></td></tr></table>
<blockquote><p>Ofcourse the quoted text after <code>CONSTRAINT=</code> should be properly encoded for HTTP</p></blockquote>
<h1>History</h1>

<p>The module is derived from the old <a href="http://svn.geotools.org/geotools/trunk/gt/modules/library/main/src/main/java/org/geotools/filter/ExpressionBuilder.java">org.geotools.filter.ExpressionBuilder</a> parser by Ian Schneider.</p>

<p>The focus was to fully support the 2.0.1 version of the BNF as defined in the CSW spec. This implies, among other improvements:</p>
<ul class="alternate">
	<li>support for nested and prefixed property names (for example, <code>gmd:MD_Metadata.identificationInfo.gmd:MD_DataIdentification.abstract</code>)</li>
	<li>support for spatial predicates (intersect, touches, etc). Note that the BNF oddly suppressed the trailing 's' from these predicates, so <code>TOUCH(ATTR1, POINT(1 2))</code> instead of <code>TOUCHES(ATTR1, POINT(1 2))</code></li>
	<li>temporal predicates (BEFORE, AFTER, DURING, etc)</li>
</ul>

<h1>Design Overview</h1>

<p>The diagram presents the cql module <strong>published</strong> interface. The showed classes, <strong>CQL</strong> and <strong>ECQL</strong>, implement the contract with the clients. You can find other public classes in packages such as <strong>common</strong> and <strong>generated</strong>, but they are intended as internal interface (part of the implementation). They are not part of CQL module contract, so you should not use those classes.</p>

<p><img class="confluence-embedded-image" src="/download/attachments/231079965/org.geotools.filter.text+-+module+interface.jpg?version=1&amp;modificationDate=1369170831478" data-image-src="/download/attachments/231079965/org.geotools.filter.text+-+module+interface.jpg?version=1&amp;modificationDate=1369170831478" data-linked-resource-id="231374894" data-linked-resource-type="attachment" data-linked-resource-default-alias="org.geotools.filter.text - module interface.jpg" data-base-url="http://docs.codehaus.org" data-linked-resource-container-id="231079965" title="null > org.geotools.filter.text - module interface.jpg"></p>

<p>In the below figure are presented the main package relations. The <strong>generated</strong> package maintains all classes generated by <strong>javacc</strong>. The <strong>cql2</strong> and <strong>ecql</strong> packages implement the parsing and filter construction for OGC CQL and ECQL languages, respectively. In the <strong>commons</strong> are encapsulated the utility classes required to implement the module behavior.   </p>

<p><img class="confluence-embedded-image" src="/download/attachments/231079965/org.geotools.filter.text+-+package+relations.jpg?version=1&amp;modificationDate=1369170831461" data-image-src="/download/attachments/231079965/org.geotools.filter.text+-+package+relations.jpg?version=1&amp;modificationDate=1369170831461" data-linked-resource-id="231374893" data-linked-resource-type="attachment" data-linked-resource-default-alias="org.geotools.filter.text - package relations.jpg" data-base-url="http://docs.codehaus.org" data-linked-resource-container-id="231079965" title="null > org.geotools.filter.text - package relations.jpg"></p>

<p>To know more about CQL module implementation, see the following links:</p>

<ul>
	<li><a class="confluence-link" href="/display/GEOTOOLS/CQL+Parser+Design" data-linked-resource-id="67669" data-linked-resource-type="page" data-linked-resource-default-alias="CQL Parser Design" data-base-url="http://docs.codehaus.org">CQL Parser Design</a></li>
	<li><a class="confluence-link" href="/display/GEOTOOLS/ECQL+Parser+Design" data-linked-resource-id="110493908" data-linked-resource-type="page" data-linked-resource-default-alias="ECQL Parser Design" data-base-url="http://docs.codehaus.org">ECQL Parser Design</a></li>
</ul>

<h1>Status</h1>

<p>The module is in good health. No self or transient issues preventing it from compiling and passing tests.</p>