[OpenLayers-Users] Is there any way to avoid loading spatial data when using OpenLayers.Control.GetFeature?

[Michael O'Cleirigh]

Hello,

I have a WMS layer containing various polygons that are used to 
subdivide a map.  The boundaries run along the street center line and 
rivers, etc. It is a transparent layer sitting on top of google maps.

When the user clicks on the map I want to use WFS to get the zone number 
of the polygon that contains the clicked point.

But the problem is that I don't need the geographic detail of the zone.  
I add the zone number into the WMS layer logical filter which toggles 
the polygon visibility.

Because the performance is slow I want to avoid fetching the spatial 
data as part of the WFS request.

In the browser I can add a 'propertyName' parameter and this will 
constrain the attributes returned to only include the zone number (i.e. 
to exclude the spatial column).  But I can't figure out how to do this 
to a OpenLayers.Protocol.WFS object.

Does anyone have an example of how I can do this? or do I need to craft 
a custom OpenLayers.Request call?

Thanks for your help,

Mike

References:

The control is registered as:

control = new OpenLayers.Control.GetFeature( {
        protocol : OpenLayers.Protocol.WFS.fromWMSLayer(wmsLayer),
        box : false,
        hover : false,
        multiple : false,
        click : true,
        clickout : false,
        toggle : false,
        clickTolerance : 0,
        maxFeatures : 5

    });

My click hander is:

control.events.register("featureselected", this, function(e) {

        // get the zone number from the feature attributes returned 
through WFS
            var selectedZone = e.feature.attributes[this.zoneFilterName];

            if (this.containsZone(selectedZone) == 1) {
                // this is a remove
            this.removeZoneFromFilter(selectedZone);
      
        } else {
            // this is an add
            this.addZoneToFilter(selectedZone);
      
        }
      
        // update the filters on this.wmsLayer
        this.update();

    });


In Browser WFS request:

If I run the WFS GET query in the browser I can add a propertyName 
parameter that will cause only that named value to be returned

http://10.0.16.100:8081/geoserver/wfs?request=GetFeature&service=WFS&version=1.1.0&typeName=zone_boundary&srs=urn:x-ogc:def:crs:EPSG:900913&maxfeatures=1&propertyName=zoneNumber

Response:

<wfs:FeatureCollection numberOfFeatures="1" 
timeStamp="2009-08-11T11:56:30.764-04:00" 
xsi:schemaLocation="http://10.0.16.100:8081/geoserver/wfs?service=WFS&version=1.1.0&request=DescribeFeatureType&typeName=zone_boundary 
http://www.opengis.net/wfs 
http://10.0.16.100:8081/geoserver/schemas/wfs/1.1.0/wfs.xsd">

<gml:featureMembers>

<GEO:zone_boundary gml:id="zone_boundary.nfm--7e5195b1_1230a1029de_-76c4">
<GEO:zoneNumber>1</GEO:zoneNumber>
</GEO:zone_boundary>
</gml:featureMembers>
</wfs:FeatureCollection>