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Re: ACTION-178: What is ISSUE-116 (Axiomatic Triples for OWL R) about?

From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Date: Tue, 12 Aug 2008 15:18:26 +0100
Message-Id: <F6E039CC-8C9D-4B24-A97E-1469DEE4C82E@comlab.ox.ac.uk>
Cc: public-owl-wg Group WG <public-owl-wg@w3.org>, Ivan Herman <ivan@w3.org>, Zhe Wu <alan.wu@oracle.com>
To: Michael Schneider <schneid@fzi.de>

Michael (and Ivan),

I don't have any problem with axiomatic triples in principle.  
However, while they may be (relatively) harmless in principle, I  
worry that they could be extremely damaging from an implementation  
perspective.

Presumably, making axiomatic triples be part of OWL RL (Full) would  
mean extending the rule set so that it would generate such triples.  
There could be a very large (perhaps even infinite) number of such  
triples. This might be a serious burden on implementations and lead  
to a significant degradation in performance.

I CCed Zhe on this in the hope that we can get a view on this from an  
OWL R implementer.

ian






On 11 Aug 2008, at 15:15, Michael Schneider wrote:

> [cc'ing Ivan Hermann as the raiser of ISSUE-116.]
>
> Dear WG!
>
> At F2F3, ACTION-178 was put on me to explain my understanding of
>
>   ISSUE-116: "Should Axiomatic Triples be added to OWL-R Full?"
>
> Here is my understanding, after a short explanation what axiomatic  
> triples are.
>
> (A) What are axiomatic triples?
> -------------------------------
>
> These are typical examples of axiomatic triples (taken from RDFS):
>
>   (1) rdf:Property rdf:type rdfs:Class
>   (2) rdf:type rdf:type rdf:Property
>
> These axiomatic triples specify the part of the universe to which  
> certain URIs of the "system vocabulary" belong: 'rdf:Property'  
> denotes a class, while 'rdf:type' refers to a property.
>
> Note that in RDF, there is no real distinction between the  
> vocabulary specifying the language (such as 'rdf:type'), and the  
> custom vocabulary used within an ontology. Axiomatic triples  
> interpret the system vocabulary, by telling what's true for them  
> independently of the concrete ontology, in which they are used.
>
> Axiomatic triples are defined in RDF and RDFS, and also in pD*. OWL  
> 1 Full also contains lots of axiomatic triples for the OWL  
> vocabulary, though they are written in a different notation there.
>
> (B) Which axiomatic triples do typically exist?
> -----------------------------------------------
>
> Aside of type information (as in the examples (1) and (2)), RDFS  
> also specifies the domain and range for all properties in the RDFS  
> vocabulary, e.g.:
>
>   (3) rdf:type rdfs:domain rdfs:Resource
>   (4) rdf:type rdfs:range rdfs:Class
>
> (C) What is the scope of the issue?
> -----------------------------------
>
> The main question at F2F3 was whether this issue is also about  
> *additional* genuine OWL R Full axiomatic triples, or just about  
> RDFS axiomatic triples. From Ivan's mail it becomes pretty clear  
> that this issue includes axiomatic triples, which go beyond RDFS  
> (Ivan confirmed this to me in a private mail). One of his stated  
> examples is:
>
>   "owl:FunctionalProperty,rdfs:subClassOf,rdf:Property"
>
> This assertion clearly does *not* exist in RDFS, since  
> 'owl:FunctionalProperty' doesn't belong to the RDFS vocabulary.  
> (Whether this example would be a useful axiomatic triple or not for  
> OWL R Full is not a topic here.)
>
> (D) What would be the additional axiomatic triples?
> ---------------------------------------------------
>
> Defining axiomatic triples is in most times a pretty straight  
> forward task. For all OWL URIs in the OWL R vocabulary the type is  
> stated (Resource, Class, Property), and for properties also the  
> range and domain. All axiomatic triples which I have in mind would  
> follow the examples (1) to (4) above.
>
> For example, for 'owl:complementOf', I would propose the axiomatic  
> triples:
>
>     owl:complementOf
>         rdf:type rdf:Property ;
>         rdfs:domain rdfs:Class ;
>         rdfs:range rdfs:Class .
>
> Since OWL 2 Full will also have axiomatic triples (the old ones  
> from OWL 1 Full, and new ones for the new vocabulary), OWL R Full  
> can simply take what it needs from OWL 2 Full.
>
> (E) Could additional axiomatic triples lead to problems?
> --------------------------------------------------------
>
> I suppose that if RDFS axiomatic triples do not already lead to  
> problems, then additional axiomatic triples for the OWL R  
> vocabulary will not lead to problems, either.
>
> In general, I expect axiomatic triples, as long as they have the  
> form given in (D), to be semantically harmless (well, mostly  
> harmless :)).
>
>> From a spec'ing effort perspective, adding them is an easy task (I  
>> am offering to do this, should the WG decide to add them).
>
> Regards,
> Michael
>
> --
> Dipl.-Inform. Michael Schneider
> FZI Forschungszentrum Informatik Karlsruhe
> Abtl. Information Process Engineering (IPE)
> Tel  : +49-721-9654-726
> Fax  : +49-721-9654-727
> Email: Michael.Schneider@fzi.de
> Web  : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555
>
> FZI Forschungszentrum Informatik an der Universität Karlsruhe
> Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe
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>
Received on Tuesday, 12 August 2008 14:19:08 GMT

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