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Re: RE : Suggestion for SKOS FAQ

From: Stella Dextre Clarke <stella@lukehouse.org>
Date: Fri, 14 Mar 2008 11:32:20 +0000
Message-ID: <47DA6244.8010501@lukehouse.org>
To: Antoine Isaac <Antoine.Isaac@KB.nl>
CC: Simon Spero <ses@unc.edu>, al@jku.at, iperez@babel.ls.fi.upm.es, SKOS <public-esw-thes@w3.org>

I tend to look at this question in quite a simple way.
the relationship "A NT B" says that B must be totally contained within A 
(in one of three carefully specified ways - generic, instantial or 
partitive). Likewise, "B NT C" says C is totally contained within B. It 
follows logically that C must be totally contained within A. In a 
Boolean representation, you can think of this as three concentric circles.

The thesaurus convention is not to insert a direct reference from C to 
A, not because it is logically wrong, but because it could confuse 
people to see "C NT A".

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?


Antoine Isaac wrote:
> Hi Simon,
> Two objections to your mail:
> 1. I still don't get it why ISO2788 says BT *should* be transitive. Of 
> course there can be interpretations that leads to this, but it's still 
> not 100% clear to me. Can you quote a sentence that makes you say so?
> 2. In the exemple you give, SKOS does not prohibit A broader C. We say 
> that broader is *not transitive*, that different from saying that it is 
> *intransitive* (or "antitrantisitive") ! "transitivity does not hold" 
> does *not* mean that (NOT A broader C) is valid in all cases.
> Maybe actually point 2 is an answer to point 1, if you got our proposal 
> for skos:broader semantics wrong.
> To sum up:
> - from A skos:broader B, B skos:broader C you cannot automatically infer 
> A skos:broader C: there are concept schemes for which this would be 
> assuming too much coherence for the hierarchical links.
> - there can be concept schemes for which the co-existence A skos:broader 
> B, B skos:broader C and A skos:broader C is OK. Maybe all thesauri that 
> are compliant with ISO2788, if ISO2788 say BT is always transitive. But 
> the A skos:broader C was in that case produced by some knowledge that is 
> not in the SKOS semantics.
> Does it make the situation clearer? You can also go to [1], when 
> Alistair noticed this subtle differences (that had been also interfering 
> with the SWD working group discussions)
> Best,
> Antoine
> [1] http://lists.w3.org/Archives/Public/public-esw-thes/2007Dec/0052.html
> -------- Message d'origine--------
> De: public-esw-thes-request@w3.org de la part de Simon Spero
> Date: ven. 07/03/2008 23:58
> : al@jku.at
> Cc: iperez@babel.ls.fi.upm.es; SKOS
> Objet : Re: Suggestion for SKOS FAQ
> On Fri, Mar 7, 2008 at 4:54 PM, Andreas Langegger <al@jku.at> wrote:
>  >
>  >  thanks for the pointer to issue-44. I didn't read deep into the thread.
>  > But as Antoine pointed out, there is the transitive version also 
> (obviously
>  > the result of the issue-44 discussion). So both kinds of semantics can be
>  > expressed in the model and are not defined by the application.
>  >
> The problem with the introduction of an intransitive "broader" relationship
> is that such a relationship is fundamentally incompatible with the Broader
> Term relationship as defined in ISO-2788 et. al.
> The defining characteristic of hierarchical relationships  is that they are
> totally inclusive.  This property absolutely requires transitivity.  If this
> condition does not apply, the relationship is associative, not hierarchical.
>   Renaming the broader and narrower term relationships doesn't change this;
> all it has done is cause confusion.
> As an example of the confusion so caused, note that associative
> relationships remain disjoint from broaderTransitive (S24)?    If "broader"
> can be intransitive, this constraint is inexplicable.
> Let A,B,C be Concepts,
>        A broader B,
>        B broader C,
> and suppose that transitivity does not hold (  NOT A broader C)
> By S18,  we have
>       A broaderTransitive B,
>       B broaderTransitive C,
> By S21,
>       A broaderTransitive C
> and hence, by S24,
>       NOT A related B,
>       NOT B related C,
>       NOT A related C
> We have NOT A broader C and NOT A related C, so there can't be any
> relationship between A and C  at all!
> Simon

Stella Dextre Clarke
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Received on Friday, 14 March 2008 15:02:09 UTC

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