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Re: ISSUE-79 (EL++): REPORTED: EL++ Variants

From: Bernardo Cuenca Grau <bcg@cs.man.ac.uk>
Date: Thu, 29 Nov 2007 00:58:02 +0000 (GMT)
To: Carsten Lutz <clu@tcs.inf.tu-dresden.de>
cc: OWL Working Group WG <public-owl-wg@w3.org>
Message-ID: <Pine.GSO.4.42.0711290050530.6591-100000@kiss>

> > I have a question, however, concerning the  interaction between range
> > restrictions and role inclusion axioms. Note that the EL++ version in the
> > fragments document does impose some restrictions in the use of (complex) role
> > inclusion axioms, namely the same ones as SROIQ imposes.
> The document is a bit confusing in that respect stating that "The
> language EL++, as presented here, is not a fragment of OWL DL, since
> it provides complex inclusion axioms on Object Properties."

Well, here I meant that EL++ is not contained in OWL DL, because SHOIN
does not allow for complex inclusion axioms.

>, but also
> "in particular, this document enforces the regularity condition on
> complex property inclusion axioms required in OWL 1.1. With this
> restriction, EL++ is a fragment of OWL 1.1."

What I meant is that the EL++ Tractable Fragments document imposes the
same regularity condition on the role inclusion axioms as OWL 1.1.
Therefore, the version of EL++ in this document is not strictly the same
as the one in your IJCAI-05 paper, which didn't impose regularity
conditions. Also, I included range restrictions because I thought they
were harmless, but now I see this has to be checked out. In short, if you
can check that the role inclusion axioms and the range restrictions do not
interact badly under regularity conditions, then the document is all
right. I agree that these statements should be made clearer.


> > My question is
> > whether these restrictions are not sufficient.  If they do not suffice, I
> > agree with Carsten in that identifying a variant of EL++ that allows for
> > domain and range and imposes reasonable constraints in the use of role
> > inclusion axioms would be  a good thing to have and that version should be
> > the one included in the document.
> I suppose that they are sufficient, but I never checked the details.
> Actually, these restrictions were precisely what I meant in my last
> mail when talking of a new variant. So there is actually no disagreement
> here, only somebody has to verify that things remain tractable. I'll
> try to do that until the Manchester F2F.
> > I think that the issue whether this fragment which should be called ``OWL
> > Light" is a much more controversial one. In principle I think there should be
> > no single ``OWL Light'', but a reasonable menu of choices for such an OWL
> > Light that each particular user could pick depending on his application
> > needs.
> I disagree for the reasons given in my mail(s). Anyway, we should maybe
> not mix these two issues.
> greetings,
>  		Carsten
> --
> *      Carsten Lutz, Institut f"ur Theoretische Informatik, TU Dresden       *
> *     Office phone:++49 351 46339171   mailto:lutz@tcs.inf.tu-dresden.de     *

Dr. Bernardo Cuenca Grau
Research Fellow
Information Management Group
School Of Computer Science
University of Manchester, UK
Received on Thursday, 29 November 2007 00:58:14 UTC

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