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Re: [SKOS] ISSUE-83 semantics of scheme containment properties

From: Antoine Isaac <aisaac@few.vu.nl>
Date: Mon, 28 Jul 2008 17:13:51 +0200
Message-ID: <488DE22F.8050501@few.vu.nl>
To: Alistair Miles <alistair.miles@zoo.ox.ac.uk>
CC: "'Sini, Margherita \(KCEW\)'" <Margherita.Sini@fao.org>, public-swd-wg@w3.org

Hi Alistair,

Back to this issue: what is a valid "condition"?

The Reference says that "the formal definitions and integrity conditions 
are stated throughout using prose" [1]
It does not really rule out some kind of prose, except maybe with the 
(soft) constraint "generally follows the style used in [@@REF-RDFS], and 
should be clear to a reader with a working knowledge of RDF and OWL."

But I really do not see how this could rule out any prose that would 
actually mirror a valid OWL definition.

Cheers,

Antoine

[1] http://www.w3.org/2006/07/SWD/SKOS/reference/master.html#L1291
> Hi Margherita,
>
>   
>> If this can help, I think that
>>     
>>> ex:cs skos:hasTopConcept ex:c.
>>> entails
>>> ex:c skos:inScheme ex:cs
>>>       
>> is enough... 
>>     
>
> Well, like I said to Antoine, although this is fine for the notes sections, I'm not sure it is enough for the class & property definitions. 
>
> Usually an entailment follows from some underlying condition, which is part of the data model. Currently the SKOS Reference tries to always state the underlying condition, rather than simply state the entailments. 
>
> I'm concerned that, if we were to just state the entailments, we could run into problems. For example, what happens then if somebody declares a sub-property of skos:hasTopConcept? Maybe the answer is obvious, I'm not sure. 
>
> The underlying condition is either that the (as yet unnamed) inverse of skos:hasTopConcept is a sub-property skos:inScheme, or (equivalently?) that skos:hasTopConcept is a sub-property of the (as yet unnamed) inverse of skos:inScheme. 
>
> I think that one of those two conditions needs to be stated somehow in the class & property definitions. 
>
> The most straightforward way I can think of to do that is to give the inverse of skos:hasTopConcept a name. This means that we don't have to invent any new language for the class & property definitions in section. We can just say "skos:topConceptInScheme is a sub-property of skos:inScheme. skos:topConceptInScheme is the owl:inverseOf the property skos:hasTopConcept." These have obvious meaning in RDFS/OWL.
>
>   
>> because technically we do not gain any new information by
>> entering a new property such "skos:topConceptInScheme "... We can just
>> extract all topConcept with a query.
>>     
>
> Yes, but see above ... I think we need some way to state the underlying condition on the data model.
>
> Any further thoughts?
>
> Cheers,
>
> Alistair.
>
>
>   
>> hope this helps
>> Margherita
>>
>> 	-----Original Message-----
>> 	From: public-swd-wg-request@w3.org on behalf of Antoine Isaac
>> 	Sent: Sat 7/26/2008 00:44
>> 	To: Alistair Miles
>> 	Cc: public-swd-wg@w3.org
>> 	Subject: Re: [SKOS] ISSUE-83 semantics of scheme containment
>> properties
>>
>>
>>
>>
>> 	Hi Alistair,
>>
>> 	I agree that the first solution you propose makes the trick from
>> a
>> 	semantic perspective. But I don't like having an extra vocabulary
>> 	element just for this...
>>
>> 	I had actually written [1] to look a bit like the general
>> entailments
>> of
>> 	the SKOS Reference, thinking that we could  just have:
>> 	> ex:cs skos:hasTopConcept ex:c.
>> 	> entails
>> 	> ex:c skos:inScheme ex:cs
>> 	>
>>
>> 	Otherwise I think you can indeed introduce a non-named property
>> in an
>> 	OWL axiom, like (hoping I'm not making any mistake...)
>>
>> 	skos:hasTopconcept rdfs:subPropertyOf [ a owl:ObjectProperty;
>> 	owl:inverseOf skos:inScheme .] .
>>
>> 	Again, I would definitively favor one of these two options over
>> 	introducing a new property.
>>
>> 	Cheers,
>>
>> 	Antoine
>>
>> 	[1]
>> http://lists.w3.org/Archives/Public/public-swd-wg/2008May/0068.html
>>
>>
>> 	> Hi Antoine,
>> 	>
>> 	> I'm just trying to figure out how to implement the resolution
>> [1]
>> to
>> 	> issue 83 [2] in the SKOS reference.
>> 	>
>> 	> The most obvious way is to introduce a new property, called
>> something
>> 	> like skos:topConceptInScheme, and introduce two new statements
>> into
>> the
>> 	> SKOS data model, that skos:topConceptInScheme is a sub-property
>> of
>> 	> skos:inScheme, and that skos:topConceptInScheme is the inverse
>> of
>> 	> skos:hasTopConcept.
>> 	>
>> 	> Another way would be to avoid introducing any new properties,
>> and
>> to
>> 	> include a new statement in the data model, something like, "the
>> inverse
>> 	> of skos:hasTopConcept is a sub-property of skos:inScheme", or
>> "if a
>> 	> scheme has a top concept, then the top concept is in that
>> scheme",
>> 	> or ... ?
>> 	>
>> 	> At the moment I favour the first approach. It has an obvious
>> meaning in
>> 	> terms of RDFS/OWL. The second approach has no obvious
>> translation
>> in
>> 	> RDFS/OWL, and is difficult to word.
>> 	>
>> 	> What do you think?
>> 	>
>> 	> Cheers,
>> 	>
>> 	> Al.
>> 	>
>> 	> [1]
>> http://lists.w3.org/Archives/Public/public-swd-wg/2008May/0068.html
>> 	> [2] http://www.w3.org/2006/07/SWD/track/issues/83
>> 	>
>> 	>
>>
>>
>>
>>     
>
> --
> Alistair Miles
> Senior Computing Officer
> Image Bioinformatics Research Group
> Department of Zoology
> The Tinbergen Building
> University of Oxford
> South Parks Road
> Oxford
> OX1 3PS
> United Kingdom
> Web: http://purl.org/net/aliman
> Email: alistair.miles@zoo.ox.ac.uk
> Tel: +44 (0)1865 281993
>
>
>
>   
Received on Monday, 28 July 2008 15:14:24 UTC

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