New answers tagged ogc
You can find the definitive answer from the OGC standards. Current Feature Encoding standard 2.0 is at http://docs.opengeospatial.org/is/09-026r2/09-026r2.html and I fear that you are right. There is an example (number 12) in the standard about this ( <fes:Or> <fes:PropertyIsEqualTo> ...
CSIRO makes them available: https://www.seegrid.csiro.au/wiki/AppSchemas/HollowWorld Also look at ShapeChange as a way to transform UML to GML
Top 50 recent answers are included