[OpenLayers-Dev] Improvements proposal : make Geoserver functions available in OL filter

Tim Schaub tschaub at opengeo.org
Thu Feb 10 12:54:47 EST 2011

I like the idea.  I've been wanting to implement something similar. 
Ideally we could serialize/deserialize with the CQL format and the 
Filter format.  And it would be nice to consider a way to evaluate 
filters with custom functions on the client as well.  I think what we 
really need is better expression support in general.

I haven't looked at your patch yet, but I like the sound of it.


On 2/10/11 10:25 AM, Ivan Grcic wrote:
> Dear devs,
> we would like to make an improvement for OL Filter, that would add the
> possibility to create Geoserver vendor ogc:Function filter elements
> inside existing spatial filter elements.
> As you probably already know,  GS has quite a lot of these handy
> functions by now, so it would be also useful to have them available in
> OL ( http://docs.geoserver.org/2.0.x/en/user/filter/function_reference.html
> )
> Recently GS filter was improved by GeoSolutions with even more
> advanced filter options that enable us to make advanced queries that
> combine different layers on Geoserver (you can read more about it on
> http://geo-solutions.blogspot.com/2011/02/developer-corner-cross-layer-filtering.html)
> I made some initial patch that achieves desired behavior, and I opened
> ticket for it (http://trac.osgeo.org/openlayers/ticket/3053)
> As I see it now, spatial filter elements accept several arguments:
> type , property, value (Geometry or BBOX), distance and distance
> units.
> With this patch it will be possible to define additional elements
> functionName and functionParams, which would be used instead of
> filter.value element to create necessary Function elements.
> In OpenLayers.Format.Filter.v1 additional writers Function elements
> was added. For each Function element two parameters have to be set:
> string functionName  and array functionParams. functionParams can
> contain various number of parameters - Literals, or another Function
> elements, allowing us to create complex filters  with nested Function
> elements.
> In OpenLayers.Format.Filter.v1_0_0  and
> OpenLayers.Format.Filter.v1_1_1 writeSpatial function check was added
> that looks if functionName  was supplied instead of value, and writes
> function node for us.
> (OpenLayers.Filter.Spatial needs to be modified I guess also to add
> additional elements there)
> So, id like to hear some comments/opinions about it, if i'm heading in
> the right directions? Should I maybe define
> functionName/functionParams inside filter.value?
> Any suggestions are more than welcomed!
> Regards,
> Ivan

Tim Schaub
OpenGeo - http://opengeo.org
Expert service straight from the developers.

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