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Re: RE : Suggestion for SKOS FAQ

From: Antoine Isaac <aisaac@few.vu.nl>
Date: Tue, 18 Mar 2008 12:40:08 +0100
Message-ID: <47DFAA18.2080601@few.vu.nl>
To: Simon Spero <ses@unc.edu>
CC: SKOS <public-esw-thes@w3.org>

Hi Simon,

Again, Stella's point is right. And what Simon cite is true: there are 
thesauri which are well structured for which transitivity is valid. But:
- I don't assume that the world only contain thesauri with valid structure
- there are other KOS than thesauri
So we can allow transitivity of skos:broader to be ok locally, over some 
SKOS, but we cannot assume it holds over the global graph of 
skos:broader (that is, all the statements that are made using it, over 
all KOSs)
That's what the current specification allows.


> On Fri, Mar 14, 2008 at 7:32 AM, Stella Dextre Clarke 
> <stella@lukehouse.org <mailto:stella@lukehouse.org>> wrote:
>     However, SKOS may not choose to apply constraints too strictly,
>     because:
>     (a) some thesauri are carelessly constructed, and may not apply
>     the standard rules very strictly, and
>     (b) other types of vocabulary do not apply all the thesaurus
>     rules, and SKOS wants to be flexible.
>     Am I right in thinking this is the SKOS mainstream view?
> I can't  speak for the mainstream :-)    Your chapter in Bean and 
> Green (2001) has been cited in support of this view, but this appears 
> to be a misreading.  To the extent that these statements are true, 
> they don't imply an intransitive semantics of 'broader':
> Dextre Clarke defines a hierarchical relationships as one "assigned to 
> a pair of terms when the scope of one of the terms totally includes 
> (is broader than) the scope of the other." (Dextre Clarke 2001, p. 42)
> Milstead confirms that total inclusion is the key criteria: "[The 
> part-whole relationship] only has to meet the test of always being 
> true, just as with the other hierarchical relationships."(Milstead 
> 2001, p.60)
> Example given in the SKOS Primer may be the result of subconsciously 
> treating  SKOS Concepts as if they were OWL Classes:
> Consider for instance a case where |ex2:vehicles| is said to be 
> broader than |ex2:cars|, which is itself asserted to be broader than 
> |ex2:wheels|. It may be debatable to automatically infer from this 
> that wheels is a narrower concept to vehicles.   (Isaac and Summers 2008)
> If SKOS Concepts are treated as if they defined sets of Things, then 
> this concern is valid.  A wheel is not a kind of vehicle.
>  However, as Fischer points out, the the standards "more or less 
> implicitly allow that these different types of hierarchy relations may 
> be conflated into one hierarchical relationship in an actual 
> thesaurus; we see this also reflected in the title "The Hierarchical 
> Relationship" (ISO 2788, 8.3)".  (Fischer 1998)
> He explains this permissiveness with reference to the document 
> retrieval definition of broader-narrower given by Soergel :
> "Concept A is broader than concept B whenever the following holds: in 
> any inclusive search for A all items dealing with B should be found. 
> Conversely B is narrower than A."(Soergel 1974, p. 78)
> If (within the scope of the controlled vocabulary) documents about 
> wheels are always about cars, and documents about cars are always 
> about vehicles, then it must be the case that all documents about  
> wheels are  documents about  vehicles, from the definition of subset.
> Since SKOS was created to  model controlled vocabularies,  the broader 
> relationship in SKOS must be transitive.
> Simon
> ------
> Dextre Clarke, Stella G (2001). "Thesaural Relationships". In: 
> Relationships in the Organization of Knowledge. Ed. by Carol A Bean 
> and Rebecca Green. Information science and knowledge management. 
> Dordrecht: Kluwer Academic Publishers. Pp. 37–52.
> Fischer, D.H. (1998). "From Thesauri towards Ontologies?". In: 
> Proceedings of the 5th ISKO Conference on Knowledge Organization. URL: 
> http://ipsi.fraunhofer.de/topas/publications/Fischer_1998.pdf.
> Isaac, Antoine and Ed Summers (2008). SKOS Primer. W3C.
> Milstead, Jessica L. (2001). "Standards for Relationships between 
> Subject Indexing Terms". In: Relationships in the Organization of 
> Knowledge. Ed. by Carol A Bean and Rebecca Green. Information science 
> and knowledge management. Dordrecht: Kluwer Academic Publishers. Pp. 
> 53–66.
> Soergel, Dagobert (1974). Indexing languages and thesauri: 
> construction and maintenance. Los Angeles: Melville Pub. Co.
Received on Tuesday, 18 March 2008 11:40:52 UTC

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