Re: XML Schema component designators usable in OWL?

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.)


Received on Thursday, 27 November 2008 12:01:22 UTC