- From: Bijan Parsia <bparsia@cs.man.ac.uk>
- Date: Thu, 27 Nov 2008 12:04:19 +0000
- To: public-owl-comments@w3.org
Hi Dan, I think the simple answer is "No, OWL is not 'able' to use XSD types by reference using component designators." More precisely, the OWL 2 spec does not set out conditions for using XSD types by reference. The OWL 2 type system is extensible by design (and in a much more precise way than OWL 1 or RDF was...i.e., we have a very clear description of how new types can be added and the effects on ontologies), so, in principle, implementations could support this. Originally, we intended for there to be two mechanisms, internal and external, for adding use defined types. However, over time, in part due to the slowness of progress on component designators and, more seriously, some issues with the Schema types, we moved to "internal only", i.e., we've only speced how to add user defined types from within owl using the constructors we've specified (which are, as far as sensible, aligned with XSD). One additional barrier was the effort to define the constraints on sensible user derived types that must be handled by conforming implementations. This includes the fact that no owl system has any prospects of handling complex types. One *could* do something along these lines by defining a restriction on the XSD schema that made it isomorphic to the syntactic restrictions in OWL 2. You would still have some issues about the interpretation of some of the datatypes. At this point, the working group (mostly because I gave up :)) decided that the demand for this feature, esp. given the internal facilities, didn't warrant the effort at this time. It's also a fairly modular piece of work, so if demand opens up, it wouldn't need a revision to the core spec to add this feature. (This is me speaking, not on behalf of the working group.) Cheers, Bijan.
Received on Thursday, 27 November 2008 12:01:22 UTC