- From: Bernard Vatant <bernard.vatant@mondeca.com>
- Date: Thu, 23 Nov 2006 16:38:54 +0100
- To: Alistair Miles <a.j.miles@rl.ac.uk>
- Cc: "Williams, Stuart (HP Labs, Bristol)" <skw@hp.com>, public-esw-thes@w3.org
Hi Alistair Happy to see you have a look at this. Mieux vaut tard que jamais :-) Since the thread has been quite long, do you want me to try and sum up the issue? Cheers Bernard Alistair Miles a écrit : > > 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 >> > -- *Bernard Vatant *Knowledge Engineering ---------------------------------------------------- *Mondeca** *3, cité Nollez 75018 Paris France Web: www.mondeca.com <http://www.mondeca.com> ---------------------------------------------------- Tel: +33 (0) 871 488 459 Mail: bernard.vatant@mondeca.com <mailto:bernard.vatant@mondeca.com> Blog: Leçons de Choses <http://mondeca.wordpress.com/>
Received on Thursday, 23 November 2006 15:39:02 UTC