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Re: DAML+RDFS: potentials for simplifications?

From: Jeen Broekstra <jbroeks@cs.vu.nl>
Date: Thu, 29 Nov 2001 11:00:39 +0100 (CET)
To: Joachim.Peer@unisg.ch
cc: tpassin%home.com%UNISG_EXTERN@unisg.ch, <www-rdf-logic@w3.org>
Message-ID: <Pine.GSO.4.40.0111291038090.7079-100000@flits.cs.vu.nl>

On Thu, 29 Nov 2001 Joachim.Peer@unisg.ch wrote:

> You say, a result of the simplified syntax is, that a
> processor would need a "set of conventions". Yes, but how
> does this differ from the current situation?

It doesn't, and I think we are touching upon the core here:
by using a set of conventions (RDF!) that seems likely to be
shared by a broader community we are increasing
interoperability. Possibly at the cost of not having the
most optimal model, but this is a typical result of a
compromise. You can't have your cake and eat it, too.

> Are you aware of any DAML interpreter which has no
> hardcoded set of DAML specific instructions?

Yes. Any RDF parser for example. Or the RDF Schema query
engine that we are currently building. Any RDF or
RDFS-specific tooling in fact.

The OIL - RDFS relationship has been set up in such a way
that compatibility works in both directions: any OIL spec is
valid RDF Schema, and an RDF Schema is a valid OIL ontology.
We have tried to layer OIL on top in such a way that as much
knowledge as possible is captured within the original RDF
Schema model, thus allowing "maximum" knowledge sharing with
less semantically aware (read: RDFS-only) tooling. That is
the suspected added bonus, which I personally think will
prove very valuable in a heterogeneous environment, where
lots of different levels of expressiveness (from simple RDF
to DAML+OIL) are required for different tasks.

Btw, there is a paper which deals with this issue, which
might interest you. The paper is from some time ago and
deals with the original OIL rather than DAML+OIL, but the
arguments still hold I think:

    http://www.cs.vu.nl/~jbroeks/papers/www10.pdf

> take for example the definition of the unionOf-construct of DAML:
>
> <rdf:Property rdf:ID="unionOf">
>   <rdfs:label>unionOf</rdfs:label>
>   <rdfs:comment>
>     for unionOf(X, Y) read: X is the union of the classes in the list Y;
>     i.e. if something is in any of the classes in Y, it's in X, and vice
> versa.
>     cf OIL OR
>   </rdfs:comment>
>   <rdfs:domain rdf:resource="#Class"/>
>   <rdfs:range rdf:resource="#List"/>
> </rdf:Property>
>
> this definition tells an RDF aware application only half
> of the story... It tells nothing about the semantic
> implications of this construct. So if one wants to have a
> DAML aware agent, one will need to tell it explicitly what
> e.g "unionOf" means.

True. But the RDFS-aware application will still know that
there is a relation called UnionOf. It will know that which
classes exist, it will know their instances and it will
understand the subsumption relation.  This in itself seems
valuable to me, but your mileage may vary of course :)

Regards,

Jeen
-- 
Jeen Broekstra                                     Vrije Universiteit
jbroeks@cs.vu.nl              Dept. of Mathematics & Computer Science
                                 de Boelelaan 1081, 1081 HV Amsterdam
                                                      The Netherlands
Received on Thursday, 29 November 2001 05:00:49 UTC

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