Hi,
I am currently working on making WMS work with complex features.
One of the main problems I am currently encountering, is that the
filters built from the SLD file are not working when applied in the
renderer, because the attributes inside them are x-paths, and they can't
be properly evaluated against the features.
However, I know that they would be evaluated perfectly if a
NameSpaceAwareFilterFactory (from app-schema) was used instead of the
default FilterFactory, correctly configured with the prefix/namespace
mappings provided by the user. So in fact the implementation to evaluate
these filters and expressions properly already exists in the system, it
is just not being used! And there are some other side issues related to
the same problem, like for example, testing whether the attributes
provided in the style really exist for proper error reporting, etc...
Of course we are talking about code in the render and main packages,
which aren't aware of app-schema.
I think namespace support should not be a specific app-schema thing, but
something provided through the system. Everywhere in the code I see
hacks where namespaces are actively thrown away, which is effectively
causing bugs when people have different properties with the same local
name but different namespaces, which should be supported. (see also
http://old.nabble.com/WFS-1.1-GetFeature-Attribute-missing-in-2.1-td30207470.html)
Why not move the implementation for the namespace awareness from
app-schema to the core of geotools, and allow the commonly used
filterfactory to be configured with namespace support?
I think this is the main milestone that needs to be reached before WMS
can support complex features. In fact I am pretty sure it is the only
issue that needs to be resolved, and it seems almost impossible to work
around it. And it would get rid of some buggy behaviour!
--
*Niels Charlier*
Software Engineer
CSIRO Earth Science and Resource Engineering
Phone: +61 8 6436 8914
Australian Resources Research Centre
26 Dick Perry Avenue, Kensington WA 6151
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