<excerpt>
[...] GML is not directly
composable with other XML languages. Entities that are described by other
languages cannot legally play the role of geographic features in GML. This
because all types of geographic features are required to derive from the GML
abstract class gml:AbstractFeatureType. Even if it were not for this
formal requirement, the lack of conventions about how to represent even simple
semantic notions in XML languages would prevent effective integration of GML
with XML languages developed independently.
The non-composability of GML requires that it absorb as application schemas the multitude of other domains to which geographical information is relevant. Failing this, non-standard mechanisms of some kind must be used to relate GML content with external data.
Indeed, GML positions itself as a universal, rather than geography-specific,
semantic standard by including its own general formalisms for collections,
assertion of properties (in a style very much like RDF), time and processes, and
reference between content in separate files (via Xlink). GML can be viewed as an
alternative not just to geography in RDF, but to RDF itself.
</excerpt>
This seems like a problem for us because some aspects of our biodiversity information are decidedly not spatial. Is this a problem with XML Schema generally or just the way it was used to create GML? Several TDWGers are getting enthusiastic about RDF, despite the cautions of McCool (referenced by Bob Morris earlier on the TDWG-GUID list). Should we go ahead and cast DarwinCore as a GML application while we gear up for a coordinated switch to RDF?
-Stan