Syntax for Intersect filter

[Berend Veldkamp]

Surely there must be someone who can help me out? I've read the OpenGis
specifications on gml and I studied the relevant source code, but I can't
get any intersect filter to work.
Here's what I have in my sld now:

<StyledLayerDescriptor version='1 0 0'>
  <NamedLayer>
    <Name>nap</Name>
    <UserStyle>
      <Title>nap</Title>
      <FeatureTypeStyle>
        <Rule>
          <Filter>
            <Intersect>
              <PropertyName>geometry</PropertyName>
              <Polygon srsName="EPSG:28992">
                <outerBoundaryIs>
                  <LinearRing>
                    <coordinates>150000,400000 180000,400000
165000,500000</gml:coordinates>
                  </LinearRing>
                </outerBoundaryIs>
              </Polygon>
            </Intersect>
          </Filter>

          <PointSymbolizer>
            <Graphic>
              <Size>5</Size>
              <Mark>
                <WellKnownName>circle</WellKnownName>
                <Fill>
                  <CssParameter name="fill">#0000ff</CssParameter>
                </Fill>
              </Mark>
            </Graphic>
          </PointSymbolizer>
        </Rule>
      </FeatureTypeStyle>
    </UserStyle>
  </NamedLayer>
</StyledLayerDescriptor>

But when I call mapserver, all I get is an empty image.
http://localhost/ms_dev/cgi-bin/mapserv?map=../map/test.map&service=wms&request=getmap&version=1.0.0&layers=nap&styles=&sld=http://localhost/sld6.xml
when I leave out the filter part from the sld it works, so there must be
something wrong there.
I'm not entirely sure about <PropertyName>, does it make any difference what
I put in there?

Thanks in advance, Berend