Create a TXT extention of CQL
-----------------------------
Key: GEOT-1666
URL: http://jira.codehaus.org/browse/GEOT-1666
Project: GeoTools
Issue Type: New Feature
Components: core cql
Affects Versions: 2.5-M0
Reporter: Jody Garnett
One of the things that blocks wider acceptance of the excellent CQL code is the
limited scope of the common query language. In GeoTools we have a more relaxed
view of a filter:
# support for spatial and comparison filters between any two expressions (CQL
is limited to: propertyName OP expr)
#= CQL: propertyName contains geometry
#- TXT: geometry contains geometry
# support for the Id filters as defined by Filter 1.0 specification
#- CQL: n/q
#- TXT: #road.1, #road.2
This request is for a new grammar (called TXT) that extends the CQL BNF to
account for these ideas. The new format should be presented as a seperate
facade class (even though behind the scenes it will share a lot of code with
the normal CQL implementation classes).
The new TXT grammar facade class is method compatible with CQL facade class:
{code}
class TXT {
String toTXT( Expression );
String toTXT( Filter );
Expression toExpression( String );
Expression toExpression( String, FilterFactory );
Filter toFilter( String );
Filter toFilter( String, FilterFactory );
List<Filter> toFilterList(String);
List<Filter> toFilterList(String,FilterFactory);
}
{code}
Existing specificaitons like CAT2 allow the specificaiton of a *queryLanguage*;
if an application wishes to make this format available to the public it is
advised that "txt" be a more expressive alternative queryLanaguage to "cql".
Here are some technical notes from Mauricio:
{panel}
That is possible, I suggest to maintain different dialects that reuse the
existent software infrastructure.
The dialects would allow:
1 - to associate the context which the specific language must be used
2- to redefine the original rules without conflict.
3- to reuse the "builders" for semantic actions
{panel}
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