- From: Alistair Miles <a.j.miles@rl.ac.uk>
- Date: Thu, 23 Nov 2006 14:58:49 +0000
- To: "Williams, Stuart \(HP Labs, Bristol\)" <skw@hp.com>
- CC: public-esw-thes@w3.org
Hi Stuart, Quick comment without having read the subsequent thread in detail ... I think you have revealed a potential inconsistency in the design of SKOS. Certainly worthy of an item in the issues list - I'll do that when I get a chance. Cheers, Alistair. Williams, Stuart (HP Labs, Bristol) wrote: > Hello, > > Firstly I am new to SKOS, so apologies if this has come up before. > > The SKOS guide (as indicated in this thread) discourages the use of owl:sameAs to establish equivalence relations between skos:Concepts because: > > <http://www.w3.org/TR/swbp-skos-core-guide/#secidentity> > "The property owl:sameAs should not be used to express the fact that two conceptual > resources (i.e. resources of type skos:Concept) share the same meaning. The property > owl:sameAs implies that two resources are identical in every way (they are in fact > the same resource). Although two conceptual resources may have the same meaning, > they may have different owners, different labels, different documentation, different > history, and of course a different future." > > However, the use of skos:subjectIndicator, defined inverse functional, is described in: > > <http://www.w3.org/TR/swbp-skos-core-guide/#secpsi> > "The property skos:subjectIndicator allows you to assert a link between a concept > and a human-readable document that provides a complete, definitive description of that concept. > ... > The skos:subjectIndicator property is an owl:InverseFunctionalProperty, which means that > if any two nodes in an RDF graph have the same value for this property, then they are the > same resource [OWL]. Therefore you can use the skos:subjectIndicator property to > indirectly identify a concept by reference to the URI of the document that is the > published subject indicator for that concept." > > So... if the same skos:subjectIndicator is asserted for two (or more) skos:Concepts then it can be inferred that they are the same skos:Concept which seems to be at odds with the desire *not* to establish such equivalences as expressed in the narrative above discouraging the use of owl:sameAs. > > Is there a reason why concept equivalences established via the skos:subjectIndicator are "good" and equivalencies established via owl:sameAs are bad? > > Thanks, > > Stuart Williams > -- > HP Labs, Bristol. > >> Hi, >> >> There is a confusion of different things here. >> >> 1- skos:Concept is a class. >> 2- instances of skos:Concept are called "concepts" in the SKOS documents. >> >> 3- mapping of skos:Concept to another class can be done with >> owl:equivalentClass >> 4- mapping of instances of skos:Concept to other skos:Concept >> instances (from other vocabularies) can be done with owl:sameAs >> 5- mapping of instances of skos:Concept to other instances (from other >> vocabularies) can also be done with the SKOS mapping properties, e.g. >> exactMatch [1] >> >> Now the confusion is about which kind of mapping (3-5) is meant. The >> "Concept Identity and Mapping" section [2] states that mapping type 4 >> should not be used, instead type 5 is better. This is because the >> former states that they are the same *in every respect*, while the >> latter only states that their extensions are the same (set of docs >> indexed with one concept is also properly indexed with the other). If >> you use the former you also merge their metadata, e.g. date of >> creation and scheme they belong to. They become indistinguishable. The >> latter keeps them distinguishable. >> >> The text mentioned does not refer to type 3 at all. This mapping would >> be required if someone is not using the SKOS schema for a vocabulary, >> but something similar. Then a mapping >> >> skos:Concept owl:equivalentClass my:Concept >> >> can be used to make all instances of my:Concept also skos:Concepts, so >> they can be manipulated by software that understands SKOS. >> >> Hope this helps, >> Mark. >> >> [1]http://www.w3.org/2004/02/skos/mapping/spec/#exactMatch >> [2]http://www.w3.org/TR/2005/WD-swbp-skos-core-guide-20051102/#secidentity >> >> Nabonita Guha wrote: >>> */Bernard Vatant <bernard.vatant@mondeca.com>/* wrote: >>> >>> >A skos:Concept is not a class, and the domain of owl:equivalentClass is >>> >owl:Class >>> >>> Whereas in SKOS Core guide >>> (http://www.w3.org/TR/2005/WD-swbp-skos-core-guide-20051102/#secconcept), >>> skos:Concept has been described as a class. If it's not a Class then >>> what it can be considered as? >>> >>> Best, >>> >>> Nabonita Guha >>> >>> Senior Research Fellow >>> Documentation Research & Training Centre >>> Indian Statistical Institute >>> Bangalore INDIA >>> >>> >>> >>> >>> >>> Hi Andrew >>> > The SKOS guide [1], in the "Concept Identity and Mapping" >>> section, states that owl:sameAs *should not* be used to indicate >>> that two concepts share the same meaning. It gives some rationale in >>> the section for this. Looking at the OWL guide [2], in the "4.1. >>> Equivalence between Classes and Properties" section, I'm wondering >>> whether one can use owl:equivalentClass to indicate that two >>> concepts share the same meaning. If there is a reason why >>> owl:equivalentClass can/cannot be used for this, should it also be >>> mentioned in "Concept Identity and Mapping" section? >>> > >>> Yes, there is a good reason. >>> A skos:Concept is not a class, and the domain of owl:equivalentClass is >>> owl:Class >>> >>> Cheers >>> >>> Bernard >>> >>> > >>> > Thanks, Andy. >>> > >>> > [1] >>> > [2] >>> > >>> > >>> > >>> >>> -- >>> >>> *Bernard Vatant >>> *Knowledge Engineering >>> ---------------------------------------------------- >>> *Mondeca** >>> *3, cité Nollez 75018 Paris France >>> Web: www.mondeca.com >>> ---------------------------------------------------- >>> Tel: +33 (0) 871 488 459 >>> Mail: bernard.vatant@mondeca.com >>> Blog: Leçons de Choses >>> >>> >>> >>> ------------------------------------------------------------------------ >>> Want to start your own business? Learn how on Yahoo! Small Business. >>> <http://us.rd.yahoo.com/evt=41244/*http://smallbusiness.yahoo.com/r-index> >> -- >> Mark F.J. van Assem - Vrije Universiteit Amsterdam >> markREMOVE@cs.vu.nl - http://www.cs.vu.nl/~mark > -- Alistair Miles Research Associate CCLRC - Rutherford Appleton Laboratory Building R1 Room 1.60 Fermi Avenue Chilton Didcot Oxfordshire OX11 0QX United Kingdom Web: http://purl.org/net/aliman Email: a.j.miles@rl.ac.uk Tel: +44 (0)1235 445440
Received on Thursday, 23 November 2006 14:59:18 UTC