[Geoserver-devel] WFS functions

Hi list,

Is there any documentation on using functions in a WFS request? I'm using version 1.3-RC1 now. A lot of functions are listed in the Capabilities-doc, but can't find out how to use them. I'm especially interested in the spatial functions, like intersection, bufferWithSegments, geomLength etc. As far as I can understand these are JTS functions, but how to use them in a WFS request?

For example, when using this request (based on the FES1.0 specs):

<?xml version="1.0" encoding="iso-8859-1"?>
<GetFeature outputFormat="GML2" xmlns:gml="http://www.opengis.net/gml&quot;&gt;
<Query typeName="topp:tasmania_roads">
<Filter>
   <PropertyIsGreaterThan>
     <Function name="geomLength">
       <PropertyName>topp:the_geom</PropertyName>
     </Function>
     <Literal>1</Literal>
   </PropertyIsGreaterThan>
</Filter>
</Query>
</GetFeature>

This serviceexception is thrown:

       org.xml.sax.SAXException: Attempted to construct illegal filter - I dont understand the tag: Function. HINT: tags are case-sensitive!

So can these functions be used (since Function is not recognized) and if so, how? And the numArgs is provided, but how can one know what arguments should be provided?

Thijs