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RE: SKOS Comment: skos:broader as subproperty of broaderTransitive seems backwards

From: Booth, David (HP Software - Boston) <dbooth@hp.com>
Date: Mon, 1 Dec 2008 14:49:12 +0000
To: Antoine Isaac <aisaac@few.vu.nl>
CC: "public-swd-wg@w3.org" <public-swd-wg@w3.org>
Message-ID: <CD2B872281385A439B98164F5351E6DD39C47792EF@GVW1144EXB.americas.hpqcorp.net>

Hi Antoine,

The explanation in the primer looks excellent:
http://www.w3.org/TR/2008/WD-skos-primer-20080829/#sectransitivebroader
I was looking at the SKOS Reference, and hadn't noticed the explanation in the primer.  Sorry!  Perhaps a link to that primer section would help: "See Primer sec. 4.5 for further explanation of transitivity and why skos:broader inherits from skos:broaderTransitive" (with a link).


David Booth, Ph.D.
HP Software
+1 617 629 8881 office  |  dbooth@hp.com
http://www.hp.com/go/software

Statements made herein represent the views of the author and do not necessarily represent the official views of HP unless explicitly so stated.


> -----Original Message-----
> From: Antoine Isaac [mailto:aisaac@few.vu.nl]
> Sent: Monday, December 01, 2008 8:54 AM
> To: Booth, David (HP Software - Boston)
> Cc: public-swd-wg@w3.org
> Subject: Re: SKOS Comment: skos:broader as subproperty of
> broaderTransitive seems backwards
>
> Hi David,
>
> There is a small note in the SKOS Primer about this issue
> [1]. Your feedback on whether this is appropriate would be
> warmly welcome!
>
> Best regards,
>
> Antoine Isaac
>
> [1] http://www.w3.org/TR/2008/WD-skos-primer-20080829/#sechierarchy
>
>
> > Hi Sean,
> >
> > Good point and explanation!  So skos:broader does have
> *some* transitivity, but it is only transitive to the extent
> that a skos:broader relations is a skos:broaderTransitive
> relation -- the semantics of skos:broader that are distinct
> from the semantics of skos:broaderTranstive are not transitive.
> >
> > It might be worth adding or linking to your explanation in
> a future draft, since others may puzzle over this also.
> >
> > Thanks
> >
> > David Booth, Ph.D.
> > HP Software
> > +1 617 629 8881 office  |  dbooth@hp.com
> > http://www.hp.com/go/software
> >
> > Statements made herein represent the views of the author
> and do not necessarily represent the official views of HP
> unless explicitly so stated.
> >
> >
> >> -----Original Message-----
> >> From: Sean Bechhofer [mailto:sean.bechhofer@manchester.ac.uk]
> >> Sent: Monday, December 01, 2008 5:18 AM
> >> To: Booth, David (HP Software - Boston)
> >> Cc: public-swd-wg@w3.org
> >> Subject: Re: SKOS Comment: skos:broader as subproperty of
> >> broaderTransitive seems backwards
> >>
> >>
> >> On 1 Dec 2008, at 07:50, Booth, David (HP Software - Boston) wrote:
> >>
> >>> In
> >>> http://www.w3.org/TR/2008/WD-skos-reference-20080829/#L2413
> >>> it says that "skos:broader is not a transitive property", but
> >>> "skos:broader is a sub-property of
> skos:broaderTransitive, which is
> >>> a transitive property".  Isn't this backwards?
> >>>
> >>> By the entailment rules for rdfs:subPropertyOf
> >>> http://www.w3.org/TR/rdf-mt/#rulerdfs7
> >>> if:
> >>>         skos:broader rdfs:subPropertyOf skos:broaderTransitive .
> >>>         uuu skos:broader yyy .
> >>>
> >>> then necessarily:
> >>>
> >>>         uuu skos:broaderTransitive yyy .
> >> David
> >>
> >> A subproperty of a transitive property is not necessarily
> transitive.
> >> As you rightly point out, if I have
> >>
> >> xxx skos:broader yyy
> >>
> >> then I can infer
> >>
> >> xxx skos:broaderTransitive yyy
> >>
> >> However, this doesn't mean skos:broader is transitive. If
> a relation
> >> R is transitive, it means that from xRY and yRz, we can
> infer xRz. So
> >> the situation with broader is as follows.
> >>
> >> If I have
> >>
> >> xxx skos:broader yyy
> >> yyy skos:broader zzz
> >>
> >> then I can infer (through subproperties) that
> >>
> >> xxx skos:broaderTransitive yyy
> >> yyy skos:broaderTransitive zzz
> >>
> >> Now, due to the transitivity of broaderTransitive, I can infer
> >>
> >> xxx skos:broaderTransitive zzz
> >>
> >> This *doesn't* mean that xxx skos:broader zzz, so I don't
> >> (necessarily) have transitivity of skos:broader.
> >>
> >> The WG spent some time discussing this. We believe that there are
> >> situations where we do not necessarily want skos:broader to be
> >> transitive, but the pattern we have used allows us to
> /query/ across
> >> something which includes the transitive closure of skos:broader,
> >> without us having to assert that skos:broader is itself transitive.
> >> We believe that this is the desirable situation.
> >>
> >> Hope that helps.
> >>
> >>         Sean
> >>
> >> --
> >> Sean Bechhofer
> >> School of Computer Science
> >> University of Manchester
> >> sean.bechhofer@manchester.ac.uk
> >> http://www.cs.manchester.ac.uk/people/bechhofer
> >>
> >>
> >>
> >>
> >
> >
>
>
Received on Monday, 1 December 2008 14:50:19 UTC

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