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RE: Fragments discussion, continued

From: Boris Motik <boris.motik@comlab.ox.ac.uk>
Date: Tue, 19 Feb 2008 18:01:57 -0000
To: "'Web Ontology Language \(\(OWL\)\) Working Group WG'" <public-owl-wg@w3.org>
Message-ID: <002d01c87321$849659a0$7212a8c0@wolf>


I agree with this proposal in most of its main points; however, I do believe that there is a strong case for adding DLP to the list
of the official fragments. Here is why I believe that this is so:

- DLP is distinguished by the fact that you can do reasoning by looking only at the individuals explicitly introduced in the
ontology. Many simple implementations of OWL will actually implement precisely this fragment.

- DLP seems to be the perfect vehicle for explaining the relationship between OWL Prime and the DL fragments. The reasoning in OWL
Prime is also done by just considering the individuals explicitly present in the ABox, so there is a natural correspondence between
it and DLP. 

In fact, in view of my latter statement, we might think of having an OWL Prime/DLP fragment: OWL Prime would be the RDF face and DLP
would be the DL face of the same fragment. Please note that I do not propose to use these names; the name "DLP" as such is not
important to me. I just believe that, even on the DL side, there is a strong case for having a fragment such as DLP.



> -----Original Message-----
> From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org] On Behalf Of Alan Ruttenberg
> Sent: 19 February 2008 15:27
> To: Web Ontology Language ((OWL)) Working Group WG
> Subject: Fragments discussion, continued
> It seems (I hope) we are getting closer to some sort of mutual
> understanding of our needs for fragments. I'd like to sketch out the
> shape of what I'd be happy to see as an outcome of tomorrow's meeting.
> I think we've heard convincing arguments that having a large number
> of fragments in Rec track, absent strong justification for each,
> isn't desirable. On the other hand, I'd like to put forward that
> there are compelling reasons to acknowledge OWL Lite, in the manner
> I've proposed, and to put 3 fragments on rec track, and proceed in
> subsequent meetings to nail down details of specification and
> documentation.
> The fragments:
> 1) OWL Prime (details of exactly what is in or out of OWL Prime
> remain to be worked out). Justified by specific industry interest
> from Oracle and HP, and to address the constituency that wishes to
> have a workable and more easily understandable rule-based OWL.
> 2) EL++. Justified by existing academic and commercial
> implementations, useful computational properties (polytime) and
> demonstrated use for working with important ontologies for
> biomedicine, a field which has been at the leading edge of Semantic
> Web adoption.
> 3) A fragment characterized by scalability to large numbers of
> instances (not necessarily scalable tbox) , but with strong
> guarantees with respect to completeness and consistency detection.
> This is probably DL-Lite, but I want to leave the door open to input
> from IBM, who's SHER implementation might also fit the bill. We
> haven't discussed this fragment much, so I'll give my view of why it
> is justified. Such a fragment  fills a hole that neither of two other
> fragments fill, as It is likely that OWL Prime will not allow
> existentials in  a rule head (following pD*), and EL++ is not as
> scalable. In addition DL-Lite is implementable in relational
> databases with queries translatable to SQL. I have heard of two
> academic implementations ("the italians" &  Jeff Pan) and a
> commercial implementation - Clark and Parsia's, and the nature of the
> fragment is such that it would be easily adoptable by relational
> database providers. Finally, it is my judgement, as a user, that
> strong guarantees of the ability to detect inconsistency and give
> complete answers bring high value to science applications.
> To recap the OWL Lite proposal, the suggestion is to keep OWL Lite,
> unchanged, to support existing users, verify that it behaves as
> before using OWL 1.1 DL semantics, and write a Note to explain its
> status.
> Remaining fragments in the current Fragments document, would be
> described in one or more WG Notes.
> My hope would be to not necessarily work out all the details
> tomorrow, but instead to come to agreement on this number of
> fragments (3) and their character, so that subsequent meetings  can
> be focused on implementation rather than policy.
> Regards,
> Alan
Received on Tuesday, 19 February 2008 18:03:09 UTC

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