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Re: Web Rule Language - WRL vs SWRL

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Wed, 29 Jun 2005 17:37:38 -0400
To: Ian Horrocks <horrocks@cs.man.ac.uk>
Cc: Bijan Parsia <bparsia@isr.umd.edu>, Jim Hendler <hendler@cs.umd.edu>, www-rdf-rules@w3.org, dreer@fh-furtwangen.de, Jos de Bruijn <jos.debruijn@deri.org>
Message-Id: <20050629213739.6921D19E75F@kiferdesk.lmc.cs.sunysb.edu>


> On 29 Jun 2005, at 19:09, Michael Kifer wrote:
> 
> >
> >> On 28 Jun 2005, at 20:17, Michael Kifer wrote:
> >>
> >>>
> >>> Ian,
> >>>
> >>> The difference is really between SWRL and everything else,
> >>
> >> I don't understand what leads you to this bizarre conclusion! (See
> >> comments bellow w.r.t. your N3 argument.)
> >
> >
> > I don't understand your argument either.
> 
> The difference is that I *have* an argument - what you have is just a 
> statement.

Actually, I misused the word "argument".  You certainly didn't provide any
argument above.


> >>> and SWRL should
> >>> be developed by a different WG, if there is a need for a rules 
> >>> language
> >>> sitting on top of OWL.
> >>
> >> OK, so you favour option (c) - several working groups developing
> >> unrelated rules languages. Interesting plan. Surely we should try to 
> >> do
> >> something better than that.
> >
> >
> > Do you have a better plan (and reasons to believe that it will 
> > succeed)?
> 
> Yes, I believe that I *do* have a better plan. Like Bijan, I would like 
> to see "a task force, or working group, or *something*" develop a 
> framework that allows for multiple language types to co-exist in the 
> semantic web without giving up completely on interoperability. As has 
> been discussed in various of these threads, there is already promising 
> work in this direction from several groups, and so every reason to 
> think that such an effort can succeed *if only we have the will to do 
> it*.

This is not exactly a plan, but a good goal. I don't think it can be done
by a committee effectively, but I might be pleasantly surprised.


> >>> N3 is essentially a different syntax for F-logic and its extensions
> >>> (but
> >>> N3's semantics is defined by use cases ;-). As far as I can tell, 
> >>> with
> >>> each
> >>> new presentation that I hear N3 is moving in the direction of LP.
> >>
> >> I think that we should stick to discussing how things actually *are*
> >> rather than directions in which you hope/believe they might be moving.
> >
> > I am discussing things as they already are. N3 now has a form of SNAF.
> 
> Maybe, but this doesn't make it LP - we have long since known how to 
> support a form of SNAF in DL using the so-called K operator.

What makes something an LP language?

> N3 is also 
> based on RDF, and RDF does not make a CWA and so if fundamentally 
> incompatible with LP (as you seemed to agree in an answer to an earlier 
> email - see below).

Disagree.

> >> Surely N3 is *actually* a different syntax for RDF, plus some 
> >> rule-like
> >> extensions. As we have already agreed, LP is semantically incompatible
> >> with RDF, so it does not make sense to say that N3 can be included in
> >> LP.
> >
> >
> > Did we agree about RDF?  I didn't notice that.
> 
> To quote from one of your earlier emails:
> 
> > Your argument is well-taken. However, if you are querying an ontology 
> > with
> > an LP language then you expect that CWA will be applied in the current
> > state.
> > That is, if your DLP ontology says that John has one child, Bill, and
> > nothing else, then your query "get all people who have exactly one 
> > child"
> > (a query like the one in your paper) is expected to return John, since 
> > in
> > the current state he is not known to have more children.
> 
> So, an LP language would find an entailment that is *not* supported by 
> RDF semantics (which would allow for models in which John had other 
> children). Ergo, LP is semantically incompatible with RDF.

You misunderstood my reply.
I meant that I acknowledged your point about more expressive languages
not giving the same answers when they are both applied to the same dataset.

RDF by itself doesn't have any queries defined over it, so it is
meaningless to claim that a query language L over RDF syntax is
incompatible with RDF. 


	--michael  
Received on Wednesday, 29 June 2005 21:38:12 GMT

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