Re: plain rules, please [was: Semantic Web Rule Language (SWRL) 0.5 released]

Dan Connolly writes:
> 
> "This syntax extends the abstract syntax of OWL".
> 
> Why?
>
> I was expecting plain old horn rules. I don't see
> why all the terms and structures from OWL-DL are
> carried into SWRL.
>

I can't speak for everyone on the committee, but I went along with
this because (1) it's important that the rule language be usable in
concert with OWL, and (2) several members of the JC were skeptical
that a rule language can be specified orthogonal to OWL and then
combined with it, while maintaining the proper semantics and desired
reasoner performance characteristics.  I think the sense was that such
orthogonality "might be nice" or even "would be nice", but until the
details can be worked out, this 0.5 version seemed like a good
waypoint.  A future language with orthogonality should be able to be
compatible with this one, so letting folks begin coding to 0.5 seems
reasonable.

      -- sandro