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owl:sameAs (Re: RDF Recommendation Set comments (re agenda for 6th April))

From: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>
Date: Thu, 07 Apr 2011 15:24:29 +0200
Message-ID: <4D9DBB0D.6060501@liris.cnrs.fr>
To: William Waites <ww@styx.org>
CC: "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>

may be I did open this can of worm with owl:inverseOf, I'm sorry about

The point here is not to improve/augment RDFS, IMHO. It is to move into
plain RDF(S) a feature of OWL that is intensively used by people who,
otherwise, do not rely (heavily) on OWL -- namely, the linked data

Improving RDFS is a completely different matter (and probably out of
scope for the group, if I read the charter correctly). However, my gut
feeling is that introducing contradictions in RDFS would have much
bigger impacts than introducing equality... (just an intuition, though)


On 04/06/2011 08:02 PM, William Waites wrote:
> Apologies for top-posting,  writing from my phone. 
> I generally agree and have been thinking about the minimum that you
> have to take from owl to be able to derive contradictions using rdfs.
> The use case for this is debugging - detecting modelling errors. I think
> owl:disjointFrom is in the list. SameAs definitely isn't. Despite its
> clear analytical meaning for all practical purposes it means
> RelevantlySimilarTo and should not be taken literally except perhaps in
> some very well defined limited domains...
> Cheers
> Antoine Zimmermann <antoine.zimmermann@insa-lyon.fr> a écrit :
>> Le 06/04/2011 18:22, Pat Hayes a écrit :
>>> On Apr 6, 2011, at 10:19 AM, fensel wrote:
>>>> At 13:39 06.04.2011, Pierre-Antoine Champin wrote:
>>>>> On 04/06/2011 05:14 AM, Pat Hayes wrote:
>>>>>> We might want to think about incorporating some version of sameAs
>>>>>> into RDFS, as this seems to be fundamental to linked data and also
>>>>>> widely misused. Having the real meaning of equality exposed in the
>>>>>> RDF standard itself might be doing the world a favor. (?)
>>>>> +1e99
>>>> I think this may be a very bad idea. You would force all languages
>>>> layering on top of RDF to include equality.
>>> It depends what you mean by 'include'. A language based on RDF can always declare that it will use some other term and refuse to accept the RDF one, just as OWL uses owl:Thing rather than rdf:Resource.  BUt it would be more useful and more in the spirit of interoperability to use the same term and just acknowledge that it is not using all the intended meaning of that term.
>> I'd say that the comparison with OWL is not particularly appropriate. 
>> OWL Full is an extension of RDFS and as such, preserves the meaning of 
>> all the RDF/RDFS vocabularies. rdfs:Resource means the same in OWL Full. 
>> owl:Thing does not replace it.
>> OWL DL is not an extension of RDFS and it does not try to replace 
>> rdfs:Resource by owl:Thing. rdfs:Resource simply has no meaning in OWL 
>> DL while owl:Thing has a much more specific meaning than "the class of 
>> all resources". OWL DL is very different thing from RDF which just 
>> happens to be serialisable in RDF.
>>>> There are reasons
>>>> to prevent equality because it turns unification from a syntactical
>>>> operation into reasoning.
>>> Only if you claim to be logically complete. A reasoner can always just ignore the equalities, or use them in a limited but useful way. Reasoners are not *obliged* to squeeze every last drop of meaning from all the RDF they encounter. Still, the RDF means what it means :-)
>> I don't think this is a good way of doing things in a standardisation 
>> working group. People can always disregard standards or parts of it, of 
>> course. But going further in this direction, why not adding the whole 
>> OWL 2 vocabulary to RDF since reasoners are not obliged to implement it?
>> The WG should not define things that have a risk of being disregarded by 
>> implementers.
>> If one implements a system that deals with RDF, it's ok if it includes 
>> bits from RDFS but not all. Similarly, if an implementation is doing 
>> RDFS reasoning, it's ok if it include bits of OWL reasoning. But if one 
>> wants to define an extension of RDFS, it's not ok that a portion of it 
>> is disregarded. So, I'd say that adding owl:sameAs to RDFS is a pretty 
>> strong extension that needs to be pondered carefully and I find Dieter's 
>> concern quite reasonable.
>> AZ
>>> Pat
>>>> Dieter
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>> -- 
>> Antoine Zimmermann
>> Researcher at:
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>> Database Group
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>> Lecturer at:
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>> antoine.zimmermann@insa-lyon.fr
>> http://zimmer.aprilfoolsreview.com/
Received on Thursday, 7 April 2011 13:24:57 UTC

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