With Complex Features, there is the possibility of properties evaluating
to multiple values (collections of values) rather than a single value.
It should be possible to apply comparison operators (like "=", "<") and
geometry operators (like overlaps/touches/etc) to multi-valued properties.
However, the current filter system in Geotools assumes a single value
for each property.
Currently in app-schema, a work-around exists for making this work on
mapped feature collections. This work-around only works when the
filtering is applied to the mapping datastore, not when applying filters
on already built complex features. Therefore it does not work in two
situations
- in WMS styling files, it doesn't work.
- I am currently creating a new post-filtering system for a performance
improved app-schema and I cannot use the old workaround any more.
Better would be provide proper support for filtering on multiple values
in the actual filters.
I could not find any information on multi-valued properties in the OGC
filter standard. But in XPath, the standard says that when comparing
nodes with multiple values, the result should be the OR-ed aggregation
of all possible combinations. My proposal is that the same principle
would be applied to geotools filters.
Any comments?
See GEOT-3576
--
*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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