- From: Bernardo Cuenca Grau <bcg@cs.man.ac.uk>
- Date: Wed, 28 Nov 2007 18:56:50 +0000
- To: OWL Working Group WG <public-owl-wg@w3.org>
The variant of EL++ included in the Tractable fragments Document is based on the one in the 2005 IJCAI paper by Carsten and others: http://lat.inf.tu-dresden.de/~clu/papers/archive/ijcai05.pdf At the time of writing, however, I also included domain and range axioms in the description of the fragment. Obviously domain axioms are directly expressible in EL++, as described in the paper above, but this is not the case with range axioms. At the time of writing, I had some informal discussions with people, including the people in Dresden and my understanding was that range axioms, even if not directly expressible could be easily added and handled while preserving the nice properties of EL++. It seems from what Carsten says that this is not the case and therefore the variant of EL++ in the tractable fragments document seems to be broken. 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. 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 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. Bernardo OWL Working Group Issue Tracker wrote: > ISSUE-79 (EL++): REPORTED: EL++ Variants > > http://www.w3.org/2007/OWL/tracker/issues/ > > Raised by: Bijan Parsia > On product: > > (On behalf of Carsten Lutz.) > > There are at least two versions of EL++ that are tractable. These > two versions are incomparable in expressive power, and the current > document lists only one of them. The fragment that is not listed > offers both domain and range restrictions and captures, for example, > the ontology NCI. What it does not have is role inclusions. > > An obvious remedy would be to list both fragments of EL++. However, I > have hope that we can do better. We might be able to give a fragment > that (unlike the one listed at the moment) truely resides inside OWL > 1.1, that has domain and range restrictions, and that has (acyclic) > role inclusions and is still tractable. *This* is actually the > fragment that I think should be OWL Light (see ISSUE-78 on > tractable fragments). I need some time to work out details. > > > > >
Received on Wednesday, 28 November 2007 19:01:50 UTC