Re: Semantics Wrinkle

* Jeremy Carroll <jjc@hpl.hp.com> [2003-01-03 22:55+0100]
> 
> (continuing thread "Semantics Review")
> e.g.
> 
> http://lists.w3.org/Archives/Public/www-webont-wg/2002Dec/0337.html
> 
> I have been thinking some more about the text:
> [[
> Individual-valued properties that are transitive, or that have transitive 
> sub-properties, may not have cardinality conditions expressed on them, either 
> in restrictions or by being functional, or inverse functional. This is needed 
> to maintain the decidability of the language. 
> ]]


Jumping in with only partial context... I'm worried a little by the "or 
that have transitive sub-properties". It is very likely that 
rdfs:subPropertyOf will see considerable use as a relationship between 
independently invented RDF properties. It is also likely that the creators 
of an ontology/schema (unless psychic) won't have advance knowledge of 
future ontologies, so they won't know whether their ontology will need to 
be used alongside one that declares sub-properties of their various properties.
So if someone declares a property, and is wondering whether to describe 
cardinality constraints, they'll have to have a think about whether 
its likely that someone will want to make a sub-property of their property
that is transitive. If so, that's an interesting constraint on deployment
practices that could maybe get documented somewhere... (the Guide?).

(I don't think this relates to your proposed clarification Jeremy, you just 
pointed out something I hadn't noticed about OWL)

Hope this makes sense. Wish I could think of a nice example...

Dan

Received on Friday, 3 January 2003 17:21:42 UTC