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<p>This package is dedicated to support the OGC Common Query Language, version 2.0.1, as a query predicate language inside GeoTools. The rest of this document describe the syntax rules and the parser design. </p>

<p><strong>Contents</strong></p>

<p>The BNF is reproduced bellow to indicate the extensions made, which are highlighted in bold characters. The original BNF was extended thinking in SQL where expression. Moreover, we found some errors in the specification and made some corrections, that will help to use and analysis the CQL language.</p>

<h4>Syntax Rules</h4>

&lt;sequence of search conditions> ::= [1]
 			&lt;search condition>
 		|	&lt;sequence of search conditions> &lt;semicolon> &lt;search condition>

&lt;search condition> ::= &lt;boolean value expression>
</pre></td></tr></table>

&lt;boolean term> ::=
    &lt;boolean factor>
    | &lt;boolean term> AND &lt;boolean factor>

&lt;boolean factor> ::= [ NOT ] &lt;boolean primary>

&lt;boolean primary> ::=
    &lt;predicate>
    |&lt;routine invocation>
    | &lt;routine invocation>
    | &lt;left paren> &lt;search condition> &lt;right paren>
</pre></td></tr></table>

<h5>Existence Predicate</h5>

&lt;existence_predicate> :=
    &lt;attribute_name> EXISTS
    | &lt;attribute_name> DOES-NOT-EXIST

</pre></td></tr></table>

<h5>Comparison Predicate</h5>

&lt;comparison predicate> ::=
    &lt;attribute name> &lt;comp op> &lt;literal>
    | &lt;attribute name> &lt;comp op> &lt;expression>

</pre></td></tr></table>

</pre></td></tr></table>

<h5>Text Predicate (or Like Predicate)</h5>

&lt;text predicate> ::= &lt;attribute name> [ NOT ] LIKE &lt;character pattern>

</pre></td></tr></table>

&lt;character pattern> ::= &lt;character string literal>

(* pattern examples :
        attribute like '%contains_this%'
        attribute like 'begins_with_this%'
        attribute like '%ends_with_this'
        attribute like 'd_ve' will match 'dave' or 'dove'
        attribute not like '%will_not_contain_this%'
        attribute not like 'will_not_begin_with_this%'
        attribute not like '%will_not_end_with_this' *)

</pre></td></tr></table>

<h5>NULL Predicate</h5>

&lt;null predicate> ::= &lt;attribute name> IS [ NOT ] NULL

</pre></td></tr></table>

<h5>Between Predicate</h5>

&lt;between predicate> ::= &lt;attribute name> [ NOT ] BETWEEN &lt;literal> AND &lt; literal > [1]

</pre></td></tr></table>

<h5>Temporal Predicate</h5>

&lt;temporal predicate> ::=
    &lt;attribute_name> "BEFORE" &lt;date-time expression>
    | &lt;attribute_name> "BEFORE OR DURING" &lt;period>
    | &lt;attribute_name> "DURING" &lt;period>
    | &lt;attribute_name> "DURING OR AFTER" &lt;period>
    | &lt;attribute_name> "AFTER" &lt;date-time expression>

&lt;date-time expression ::= &lt;date-time> | &lt;period>

</pre></td></tr></table>

<table class="wysiwyg-macro" data-macro-name="noformat" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e25vZm9ybWF0fQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
&lt;date-time> ::= &lt;full-date> "T" &lt;UTC-time>
&lt;full_date> ::= &lt;date-year> "-" &lt;date-month> "-" &lt;date-day>
&lt;date-year> ::= &lt;digit>&lt;digit>&lt;digit>&lt;digit>
&lt;date-month> ::= &lt;digit>&lt;digit>
&lt;date-day> ::= &lt;digit>&lt;digit>
&lt;UTC-time> ::= &lt;time-hour> ":" &lt;time-minute> ":" &lt;time-second> "Z"
&lt;time-hour> ::= &lt;digit>&lt;digit>
&lt;time-minute> ::= &lt;digit>&lt;digit>
&lt;time-second> ::= &lt;digit>&lt;digit>[.&lt;digit>...]
&lt;duration> ::= "P" &lt;dur-date> | "T"&lt;dur-time>
&lt;dur-date> ::= &lt;dur-day> | &lt;dur-month> | &lt;dur-year> [&lt;dur-time>]
&lt;dur-day> ::= &lt;digit>... "D"
&lt;dur-month> ::= &lt;digit>... "M" [&lt;dur-day>]
&lt;dur-year> ::= &lt;didit>... "Y" [&lt;dur-month>]
&lt;dur-time> ::= &lt;dur-hour> | &lt;dur-minute> | &lt;dur-second>
&lt;dur-hour> ::= &lt;digit>... "H" [&lt;dur-minute>]
&lt;dur-minute> ::= &lt;digit>... "M" [&lt;dur-second>]
&lt;dur-second> ::= &lt;digit>... "S"
&lt;period> ::=
    &lt;date-time> / &lt;date-time>
    | &lt;date-time> / &lt;duration>
    | &lt;duration> / &lt;date-time>
</pre></td></tr></table>

<h5>INCLUDE/EXCLUDE Predicate</h5>

<h5>Expression</h5>

&lt;term> ::=  &lt;factor> { &lt;multiplication operator> &lt;factor> }
&lt;multiplication operator> ::= &lt;asterisk> | &lt;solidus>

&lt;factor> ::=
	  &lt;function>
	| &lt;literal>
	| &lt;attribute>
	| ( &lt;expression> )
	| [ &lt;expression> ]

</pre></td></tr></table>

&lt;function arguments> ::= &lt;literal> | &lt;attribute> | &lt;expression></pre></td></tr></table>

&lt;literal> ::= &lt;signed numeric literal>| &lt;general literal>

&lt;signed numeric literal> ::= [ &lt;sign> ] &lt;unsigned numeric literal>

&lt;general literal> ::=
    &lt;character string literal>
    | &lt;boolean literal>
    | &lt;geography literal

&lt;boolean literal> ::= TRUE | FALSE | UNKNOWN

</pre></td></tr></table>

<h5>Georutine and Relational Geooperations</h5>

&lt;routine invocation> ::=
     &lt;geoop name>&lt;georoutine argument list>
    | &lt;relgeoop name>&lt;relgeoop argument list>
    | BBOX &lt;bbox argument list>

&lt;routine name> ::= &lt; attribute name>

</pre></td></tr></table>

Since 2.6.1

</pre></td></tr></table>

&lt;bbox argument list>::= "(" &lt;attribute> ","&lt;min X> ","&lt;min Y> ","&lt;max X> ","&lt;max Y>["," &lt;crs>] ")"  [1]

&lt;min X> ::= &lt;signed numerical literal>
&lt;min Y> ::= &lt;signed numerical literal>
&lt;max X> ::= &lt;signed numerical literal>
&lt;max Y> ::= &lt;signed numerical literal>
&lt;crs> ::=  ... (* default: EPSG:4326. *)

</pre></td></tr></table>

&lt;relgeoop name> ::= DWITHIN | BEYOND

&lt;argument list> ::= &lt;left paren> [ &lt;positional arguments> ] &lt;right paren>

&lt;positional arguments> ::= &lt;argument> [ \{ &lt;comma> &lt;argument> \} ...]

&lt;argument> ::= &lt;literal> | &lt;attribute name>

&lt;georoutine argument list> ::=  &lt;left paren>&lt;attribute name>&lt;comma>&lt;geometry literal>&lt;right paren>

&lt;relgeoop argument list> ::= &lt;left paren>&lt;attribute name>&lt;comma>&lt;geometry literal>&lt;comma>&lt;tolerance>&lt;right paren>

&lt;tolerance> ::=&lt;unsigned numeric literal>&lt;comma>&lt;distance units>

&lt;distance units> ::= = "feet" | "meters" | "statute miles" | "nautical miles" | "kilometers"
</pre></td></tr></table>

<h5>Geometry Literal</h5>

&lt;Point Tagged Text> ::= POINT &lt;Point Text>

&lt;LineString Tagged Text> ::= LINESTRING &lt;LineString Text>

&lt;Polygon Tagged Text> ::= POLYGON &lt;Polygon Text>

&lt;MultiPoint Tagged Text> ::= MULTIPOINT &lt;Multipoint Text>

&lt;MultiLineString Tagged Text> ::= MULTILINESTRING &lt;MultiLineString Text>

&lt;MultiPolygon Tagged Text> ::= MULTIPOLYGON &lt;MultiPolygon Text>

&lt;GeometryCollection Tagged Text> ::=GEOMETRYCOLLECTION &lt;GeometryCollection Text>

&lt;Point Text> := EMPTY | &lt;left paren> &lt;Point> &lt;right paren>
&lt;Point> := &lt;x>&lt;space>&lt;y>
&lt;x> := numeric literal
&lt;y> := numeric literal
&lt;LineString Text> := EMPTY | &lt;left paren> &lt;Point> \{&lt;comma>&lt;Point >\}...&lt;right paren>
&lt;Polygon Text> := EMPTY | &lt;left paren>&lt;LineString Text>\{&lt;comma>&lt;LineString Text> \}...&lt;right paren&gt;
&lt;Multipoint Text> := EMPTY | &lt;left paren>&lt;Point Text>\{&lt;comma>&lt;Point Text >\}...&lt;right paren>
&lt;MultiLineString Text> := EMPTY | &lt;left paren>&lt;LineString Text>\{&lt;comma>&lt;LineString Text>\}...&lt;right paren>
&lt;MultiPolygon Text> := EMPTY | &lt;left paren>&lt;Polygon Text>\{&lt;comma>&lt;Polygon Text>\}...&lt;right paren>
&lt;GeometryCollection Text> := EMPTY | &lt;left paren>&lt;Geometry Tagged Text>\{&lt;comma>&lt;Geometry Tagged Text>\}...&lt;right paren>
&lt;Envelope Tagged Text> ::= ENVELOPE &lt;Envelope Text>
</pre></td></tr></table>

&lt;Envelope Text> ::= EMPTY |
    &lt;left paren>&lt;WestBoundLongitude>&lt;comma>
        &lt;EastBoundLongitude>&lt;comma>
        &lt;NorthBoundLatitude>&lt;comma>
        &lt;SouthBoundLatitude>&lt; &lt;right paren>
</pre></td></tr></table>
<table class="wysiwyg-macro" data-macro-name="noformat" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e25vZm9ybWF0fQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>

&lt;WestBoundLongitude> ::= numeric literal
&lt;EastBoundLongitude> ::= numeric literal
&lt;NorthBoundLatitude> ::= numeric literal
&lt;SouthBoundLatitude> ::= numeric literal
</pre></td></tr></table>

<table class="confluenceTable"><tbody>
<tr>
<th class="confluenceTh"><p> Sym </p></th>
<th class="confluenceTh"><p> Note </p></th>
<th class="confluenceTh"><p> Reference </p></th>
</tr>
<tr>
<td class="confluenceTd"><p> <img class="emoticon emoticon-information" data-emoticon-name="information" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/information.png" alt="(info)" title="(info)" /> </p></td>
<td class="confluenceTd"><p> extensions </p></td>
<td class="confluenceTd"><p> <strong>1</strong> </p></td>
</tr>
<tr>
<td class="confluenceTd"><p> <img class="emoticon emoticon-warning" data-emoticon-name="warning" border="0" src="/s/en_GB/3278/15/_/images/icons/emoticons/warning.png" alt="(warning)" title="(warning)" /> </p></td>
<td class="confluenceTd"><p> warning </p></td>
<td class="confluenceTd"><p> <strong>2</strong> </p></td>
</tr>
</tbody></table>

<h4>Lexical Rules</h4>

| &lt;simple Latin lower case letter>
&lt;simple Latin upper case letter> ::=
       A | B | C | D | E | F | G | H | I | J | K | L | M | N | O
       | P | Q | R | S | T | U | V | W | X | Y | Z
&lt;simple Latin lower case letter> ::=
       a | b | c | d | e | f | g | h | i | j | k | l | m | n | o
       | p | q | r | s | t | u | v | w | x | y | z
&lt;digit> ::=
       0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
&lt;SQL special character> ::= &lt;space>
                           | &lt;double quote>
                           | &lt;percent>
                           | &lt;ampersand>
                           | &lt;quote>
                           | &lt;left paren>
                           | &lt;right paren>
                           | &lt;asterisk>
                           | &lt;plus sign>
                           | &lt;comma>
                           | &lt;minus sign>
                           | &lt;period>
                           | &lt;solidus>
                           | &lt;colon>
                           | &lt;semicolon>
                           | &lt;less than operator>
                           | &lt;equals operator>
                           | &lt;greater than operator>
                           | &lt;question mark>
                           | &lt;left bracket>
                           | &lt;right bracket>
                           | &lt;circumflex>
                           | &lt;underscore>
                           | &lt;vertical bar>
                           | &lt;left brace>
                           | &lt;right brace>
&lt;space> ::= /*space character in character set in use
              In ASCII it would be 40*/
&lt;double quote> ::= "
&lt;percent> ::= %
&lt;ampersand> ::= &amp;
&lt;quote> ::= '
&lt;left paren> ::= (
&lt;right paren> ::= )
&lt;asterisk> ::= *
&lt;plus sign> ::= +
&lt;comma> ::= ,
&lt;minus sign> ::= -
&lt;period> ::= .
&lt;solidus> ::= /
&lt;colon> ::= :
&lt;semicolon> ::= ;
&lt;less than operator> ::= &lt;
&lt;equals operator> ::= =
&lt;greater than operator> ::= >
&lt;question mark> ::= ?
&lt;left bracket> ::= [
&lt;right bracket> ::= ]
&lt;circumflex> ::= ^
&lt;underscore> ::= _
&lt;vertical bar> ::= |
&lt;left brace> ::={
&lt;right brace> ::=}
&lt;separator> ::= { &lt;comment> | &lt;space> | &lt;newline> }...
&lt;token> ::= &lt;nondelimiter token>
            | &lt;delimiter token>
&lt;nondelimiter token> ::= &lt;regular identifier>
                        | &lt;key word>
                        | &lt;unsigned numeric literal>
</pre></td></tr></table>

<h5>Numeric</h5>
<table class="wysiwyg-macro" data-macro-name="noformat" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e25vZm9ybWF0fQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>

&lt;unsigned numeric literal> ::= &lt;exact numeric literal>
                              | &lt;approximate numeric literal>
&lt;exact numeric literal> ::=
                &lt;unsigned integer> [&lt;period>[&lt;unsigned integer> ] ]
                | &lt;period> &lt;unsigned integer>
&lt;unsigned integer> ::= &lt;digit>...
&lt;approximate numeric literal> ::= &lt;mantissa> E &lt;exponent>
&lt;mantissa> ::= &lt;exact numeric literal>
&lt;exponent> ::= &lt;signed integer>
&lt;signed integer> ::= [ &lt;sign> ] &lt;unsigned integer>
&lt;sign> ::= &lt;plus sign> | &lt;minus sign>
</pre></td></tr></table>

<h5>Delimiter</h5>
<table class="wysiwyg-macro" data-macro-name="noformat" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e25vZm9ybWF0fQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
&lt;delimiter token> ::= &lt;character string literal>
                     | &lt;SQL special character>
                     | &lt;not equals operator>
                     | &lt;greater than or equals operator>
                     | &lt;less than or equals operator>
                     | &lt;concatenation operator>
                     | &lt;double greater than operator>
                     | &lt;right arrow>
                     | &lt;left bracket>
                     | &lt;right bracket>
&lt;character string literal> ::=
                &lt;quote> [ &lt;character representation>... ] &lt;quote>
&lt;character representation> ::= &lt;nonquote character> | &lt;quote symbol>
&lt;quote symbol> ::= &lt;quote>&lt;quote>
</pre></td></tr></table>

<h5>Character String Literal</h5>

&lt;character string literal> ::=
      &lt;quote> [ &lt;character representation>... ] &lt;quote>
&lt;character representation> ::= &lt;nonquote character> | &lt;quote symbol>

&lt;quote symbol> ::= &lt;quote>&lt;quote>
</pre></td></tr></table>

<h5>Identifier</h5>
<p>The following section is intended to give context for identifier and namespaces. It assumes that the default namespace is specified in the query request and does not allow any overrides of the namepace</p>

</pre></td></tr></table>

<h3>CQL Model</h3>

<h5>CQL Interface</h5>

<p>This diagram presents the package interface. In parser's protocol methods performs the parsing of CQL and builds the the filter.</p>

<p><img class="confluence-embedded-image" src="/download/attachments/231079978/org.geotools.filter.text.cql2+-+interface+details-2.6.jpg?version=1&amp;modificationDate=1369203093390" data-image-src="/download/attachments/231079978/org.geotools.filter.text.cql2+-+interface+details-2.6.jpg?version=1&amp;modificationDate=1369203093390" data-linked-resource-id="231375020" data-linked-resource-type="attachment" data-linked-resource-default-alias="org.geotools.filter.text.cql2 - interface details-2.6.jpg" data-base-url="http://docs.codehaus.org" data-linked-resource-container-id="231079978" title="null > org.geotools.filter.text.cql2 - interface details-2.6.jpg"></p>

<h5>CQL Implementation</h5>

<p>The figure shows the principal class in the parser and build process. CQLParser does a top down analysis of the input string and makes the parsing tree. Each time CQLParser builds a node, it  makes a call to CQLCompiler, that implements the semantic actions related and builds the product or subproduct required to make the Filter at the end of the parsing process</p>

<p><img class="confluence-embedded-image confluence-thumbnail" src="/download/thumbnails/231079978/org.geotools.filter.text.cql2-implementation.jpg?version=1&amp;modificationDate=1369203093367" data-image-src="/download/attachments/231079978/org.geotools.filter.text.cql2-implementation.jpg?version=1&amp;modificationDate=1369203093367" data-linked-resource-id="231375019" data-linked-resource-type="attachment" data-linked-resource-default-alias="org.geotools.filter.text.cql2-implementation.jpg" data-base-url="http://docs.codehaus.org" data-linked-resource-container-id="231079978" title="null > org.geotools.filter.text.cql2-implementation.jpg"></p>