RE: Could owl:sameAs reference non-OWL resources?

Peter

Thanks for your answer. Some precisions below, and further question at the
end about owl:sameAs

> I'm not sure what you are trying to get at with the phrase "OWL
resource''.

I guess I mean here an XML element in an OWL document, not the (abstract)
thing represented by it (also called a resource in RDF land, right). Note
that I'm certainly biased here by the distinction made in XTM between the
following.

<resourceRef xlink:href = "foo">
used to identify the subject as *being* the information resource found at
"foo"

<subjectIndicatorRef xlink:href = "foo">
used to identify a subject *somehow defined* by the information resource
found at "foo"

I'm not sure which one of the above is the closest to owl:sameAs, if I want
to express the topic map concepts in OWL (that's what I am trying to do,
remember). In fact what I would do after your answer and a night over it,
would be to use in a Topic Map ontology a specific Datatype Property like:

      <owl:DatatypeProperty ID="subjectIndicatorRef">
            <rdfs:label>Subject Indicator</rdfs:label>
            <rdfs:domain rdf:resource="#Topic"/>
            <rdfs:range
rdf:resource="http://www.w3.org/2000/10/XMLSchema#anyURI"/>
      </owl:DatatypeProperty>

>> What about DAML legacy for instance?

> No problem, except, of course, that what you probably want is to include
> the DAML+OIL meaning for any DAML+OIL ontologies that concern this
entity,
> which you are not going to get.

I'm not sure I catch you here. Could you give an exemple?

>> Will owl:sameAs ensure backward compatibility with DAML+OIL
>> libraries? Or support XTM subject indicators? Or UDDI, XRI ... whatever.

> No.  At least not unless someone builds a system that can handle both OWL
> and DAML+OIL or XTM or UDDI, or whatever.

Well, this is indeed the kind of stuff we are up to in Mondeca. Very
arrogant indeed :))

If you have a system where the internal representation is not bound to a
specific markup, you want to be as "syntax-omnivorous" as possible and be
able to exchange files in various formats. That's why we want to be able to
swallow both XTM and OWL, and make sense of both internally if possible.
For example importing an XTM file using OWL elements as subject indicators,
we want to be able to import the properties asserted in the OWL document
about those classes. This is not completely obvious, but that's what we are
working out right now.
The round trip I was about is, if a OWL ontology can reference an XTM
subject indicator, then a system knowing how to parse both XTM and OWL
would be able to make sense of such references.

> You appear to be asking for a system that can handle
multiple formalisms.  This is not a trivial thing, and can often be very
problematic, or even impossible.

Our semantic ambition has no limits :))

Further question, BTW, this time internal to OWL universe.
How is an OWL parser supposed to deal with owl:sameAs referencing an
external OWL file? Is it supposed to parse also the referenced file? Has it
to check for consistency of properties asserted in the referenced file with
the ones asserted in the source file about the "same" individual? Has it to
import those properties, and the objects referenced by those properties,
and so on ... What happens if inconsistencies are found?
IOW, widespread use of sameAs could lead the parsing of a single file to
trigger the parsing of thousands of ontologies, if not of whole continents
of the Semantic Web... which is quite frightening.

Note that I have also found this issue in Topic Map land, where a
<topicRef> in an XTM file could in theory call another XTM file anywhere on
the Web, and trigger the same issues (except that Topic Maps can live with
inconsistencies ...). Nobody ever was able to give me a clear answer about
it, and I guess nobody has ever really implemented it.

Is this a known issue?

Thanks again for your time

Bernard

Bernard Vatant
Senior Consultant
Knowledge Engineering
Mondeca - www.mondeca.com
bernard.vatant@mondeca.com

-----Message d'origine-----
De : www-rdf-logic-request@w3.org
[mailto:www-rdf-logic-request@w3.org]De la part de Peter F.
Patel-Schneider
Envoye : lundi 28 avril 2003 13:59
A : bernard.vatant@mondeca.com
Cc : www-rdf-logic@w3.org
Objet : Re: Could owl:sameAs reference non-OWL resources?



[This is a reply to the posting of this message on www-rdf-logic.]

From: "Bernard Vatant" <bernard.vatant@mondeca.com>
Subject: Could owl:sameAs reference non-OWL resources?
Date: Mon, 28 Apr 2003 12:14:06 +0200

> Somehow a follow-up of my previous question about "things" ...
>
> I'm currently trying to figure how OWL can interoperate with legacy in
> other languages and formats, in particular DAML libraries, Topic Maps
> Published Subject Indicators, and in general any format using URIs to
> name-define "things" (or RDF resources, or Topic Maps subjects). Could be
> as well plain on-line HTML thesaurus or glossary, Dewey Classes, LoC
> Subject Headings ...
>
> Seems to me that one important aim of OWL (the main one?) should be to
use
> those URIs to achieve the "colocation objective", which is also the main
> objective of Topic Maps and Published Subjects.
>
> The colocation objective in the distributed Web environment means being
> able to assert that two "things" are identical. owl:sameAs allows to
> achieve that it seems. But what is not clear to me is if the URI
referenced
> by owl:sameAs has to define an OWL resource, or if it could be another
kind
> of resource.

I'm not sure what you are trying to get at with the phrase ``OWL
resource''.

OWL makes the assumption that all individuals (i.e., entities that are
suitable for use with properties like owl:sameAs) belong to the class
owl:Thing.  However, there are very few restrictions on what can be an
instance of owl:Thing.  In OWL DL (and OWL Lite) the only restriction is
that instances of owl:Thing can't be classes or properties or structural
elements (like rdf:nil).  In OWL Full there are no restrictions
whatsoever.

So if you are in OWL Full there are essentially no limitations on the
applicability of owl:sameAs.

> In the example given in http://www.w3.org/TR/owl-ref/
>
> <owl:Class rdf:ID="FootballTeam">
>   <owl:sameAs rdf:resource="http://sports.org/US#SoccerTeam"/>
> </owl:Class>
>
> Is "http://sports.org/US#SoccerTeam" supposed to reference an OWL
element?

Well, yes, in that anything, in OWL Full, or just about anything, in OWL DL
and OWL Lite, can be ``an OWL element''.

> What if it reference a DAML legacy for instance?

No problem, except, of course, that what you probably want is to include
the DAML+OIL meaning for any DAML+OIL ontologies that concern this entity,
which you are not going to get.

> Or an XTM topic element?

Ditto.

> Should it be converted into OWL before being used that way?

Well, as stated above, any DAML+OIL or XTM ontologies/knowledge
bases/whatever will not be understood by an OWL-only system, and thus
probably should be converted.

> IOW, will owl:sameAs ensure backward compatibility with DAML+OIL
> libraries? Or support XTM subject indicators? Or UDDI, XRI ... whatever.

No.  At least not unless someone builds a system that can handle both OWL
and DAML+OIL or XTM or UDDI, or whatever.

Why would you expect anything different.

> Otherwise said, will one be able to use owl:sameAs with the same
> flexibility as XTM <subjectIndicatorRef> which has basically the same
> semantics? The above example would read in XTM :
>
> <topic id="FootballTeam">
> 	<subjectIdentity>
> 		<subjectIndicatorRef xlink:href="http://sports.org/US#SoccerTeam"/>
> 	<subjectIdentity>
> </topic>
>
> <subjectIndicatorRef> does not assume any particular format for the
> resource at "http://sports.org/US#SoccerTeam". Could be an XML fragment,
> could be HTML, could be OWL or any other relevant syntax. The
> recommendation on Published Subjects somehow give clues on what kind of
> resource should be used that way. BTW this recommendation is currently in
> the same final draft status than OWL. See
> http://www.ontopia.net/tmp/pubsubj-gentle-intro.htm
>
> Bottom line: OWL elements can be used as Published Subject Indicators,
> provided the OWL ontology contains some specific information (like
> publisher identity, human-readable definitions ...) that can be expressed
> in OWL. So OWL should be IMO (the most) recommended format for Published
> Subject Indicators. Please note that so far it's only a personal view,
that
> I will try to push of course on the table of Published Subjects TC ASAP
> (next week).
> But to achieve the round trip, it would be cool if through owl:sameAs,
one
> could reference a Published Subject Indicator using e.g. XTM syntax.
Being
> able to ensure that round trip would be IMO a giant step towards semantic
> integration.

What round trip?  You appear to be asking for a system that can handle
multiple formalisms.  This is not a trivial thing, and can often be very
problematic, or even impossible.

> Feedback much welcome.
>
>
> Bernard Vatant
> Senior Consultant
> Knowledge Engineering
> Mondeca - www.mondeca.com
> bernard.vatant@mondeca.com


Peter F. Patel-Schneider
Bell Labs Research
Lucent Technologies

Received on Tuesday, 29 April 2003 04:51:31 UTC