- From: Carsten Lutz <clu@tcs.inf.tu-dresden.de>
- Date: Fri, 07 Mar 2008 09:45:41 +0100 (CET)
- To: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
- Cc: Jim Hendler <hendler@cs.rpi.edu>, Bijan Parsia <bparsia@cs.man.ac.uk>, "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>
On Thu, 6 Mar 2008, Ian Horrocks wrote: > > Actually, the primary idea of DL-Lite is that it has logspace data > complexity, which means that query answering can be implemented using > standard (relational) DB technology. In particular, a conjunctive query > against a DL-Lite ontology can be re-written as an SQL query against a > relational DB containing instance data. I agree, the goal of DL-Lite is: being able to answer conjunctive queries under a OWL-DL style open world semantics by storing the ABox in a relational DB, rewriting the query, and then using standard RDB query answering. This can be viewed as backward chaining and has the advantage that off-the-shelf (completely unmodified) DB technology can be used to answer conjunctive queries under an OWL-DL semantics. A slight correction though: logspace data complexity does not necessarily mean that this can be done (at least such a general result is unknown). However, the following is true: non-logspace data complexity means that this can *not* be done. greetings, Carsten > Ian > > > On 6 Mar 2008, at 19:23, Jim Hendler wrote: > >> >> I thought the primary idea of DL-Lite was that it would provide primary >> database functionality -- how can it do that without keys? >> >> >> On Mar 6, 2008, at 6:18 AM, Bijan Parsia wrote: >> >>> >>> On 6 Mar 2008, at 11:04, Ivan Herman wrote: >>> >>>> Boris, Bernardo, >>>> >>>> I went through >>>> >>>> http://www.w3.org/2007/OWL/wiki/Fragments_Proposal >>>> >>>> again today. One thing that I may have missed: I tried to see if I can >>>> use (inverse)functional properties for DL-Lite or not. I did not find any >>>> reference to those neither in 3.1 nor in 3.2. Again, I may have missed >>>> something... >>> >>> Let's see if I can discern from the text the situation. (As a test of the >>> spec.) >>> >>> In section 3: >>> http://www.w3.org/2007/OWL/wiki/Fragments_Proposal#DL-Lite >>> >>> """Several variants of DL-Lite have been described in the literature. >>> The variant presented here is called DL-LiteR since it allows for property >>> inclusion axioms; it therefore contains the intersection between RDFS and >>> OWL 1.1 DL. Other variants trade property inclusion axioms for >>> functionality and inverse-functionality of object properties.""" >>> >>> I think this is clear that functionality and inverse functionality of >>> *object* properties are forbidden. >>> >>> Actually ,the rest of the sections are quiet about data properties >>> altogether. Which would mean that data properties are forbidden in this >>> variant. Which means that it's not really the intersection of RDFS and OWL >>> 1.1 DL? >>> >>> I do think that if we make this DL Lite not have data properties, the text >>> should call that out (e.g., in the list of missing features). OTOH, I >>> think we should allow data properties ;) I would think it would be ok to >>> trade datasubproperties for keys (from a user pov)...I don't know if that >>> would be ok from the logic/impelmentation pov off the top of my had (while >>> retaining object subproperties). >>> >>> Cheers, >>> Bijan. >>> >>> >>> >> >> "If we knew what we were doing, it wouldn't be called research, would it?." >> - Albert Einstein >> >> Prof James Hendler >> http://www.cs.rpi.edu/~hendler >> Tetherless World Constellation Chair >> Computer Science Dept >> Rensselaer Polytechnic Institute, Troy NY 12180 >> >> >> >> >> > > -- * Carsten Lutz, Institut f"ur Theoretische Informatik, TU Dresden * * Office phone:++49 351 46339171 mailto:lutz@tcs.inf.tu-dresden.de *
Received on Friday, 7 March 2008 08:45:57 UTC