org.geotools.filter.text.cql2

Common Query Language (CQL)

CQL BNF with SQL Extensions

The original BNF was extended thinking in a SQL where expression. The original BNF is reproduced to indicate the extensions highlighted with bold characters.

Extensions in original BNF

	
    <SequenceOfSearchConditions > ::= 
              <search condition> 
         |    <SequenceOfSearchConditions> ";" <search condition> 
     
    
    <between predicate> ::= 
    		<attribute name> [ NOT ] BETWEEN <literal> AND < literal > 
	
    <routine invocation> ::= 
             <geoop name><georoutine argument list>
           | <relgeoop name><relgeoop argument list>
           | <routine name><argument list>
           | <BBOX> <bbox argument list>	
           
    <geoop name> ::= 
           EQUAL | DISJOINT | INTERSECT | TOUCH | CROSS | 
           WITHIN | CONTAINS |OVERLAP | RELATE [1]
      
    <bbox argument list>::= 
       "(" <attribute> ","<min X> ","<min Y> ","<max X> ","<max Y>["," <crs>] ")"
    <min X> ::= <signed numerical literal> 
    <min Y> ::= <signed numerical literal> 
    <max X> ::= <signed numerical literal> 
    <max Y> ::= <signed numerical literal>
    <crs> ::= [2]  
      
      
    [1] RELATE is not supported (implementation in GeoTools is required)
    [2] If not supplied, the BoundingBox CRS is EPSG:4326.

    

Implementation Notes

The parser was generated using javacc. In expr.jjt file you can see the input grammar for javacc required to parse CQL with extensions.

This implementation does not check CRS. The problem can be solved adding tokens (standards simbols in grammar) or checking in semantic actions consturction (FilterBuilder). The last solution requires to fix a bug retrieved the correspondent factory for crs (srs).

CQL is an acronym for OGC Common Query Language, a query predicate language whose syntax is similar to a SQL WHERE clause, defined in clause 6.2.2 of the OGC Catalog Service for Web, version 2.0.1 implementation specification.

This class provides three methods, CQL.toFilter(String) , CQL.toExpression(String) and CQL.toFilterList(String) ; and an overloaded version of each one for the user to provide a FilterFactory2 implementation to use.

Usage

We adds some extension to Common CQL thinking in convenient uses.