RE: comment: WD 10 May 2005

Also see the sections on 'classes of concepts' in http://esw.w3.org/topic/SkosDev/NiceIdeas

Cheers,

Al.


> -----Original Message-----
> From: public-esw-thes-request@w3.org
> [mailto:public-esw-thes-request@w3.org]On Behalf Of Miles, AJ 
> (Alistair)
> Sent: 25 July 2005 17:37
> To: public-esw-thes@w3.org
> Subject: RE: comment: WD 10 May 2005
> 
> 
> 
> Hi all,
> 
> Thanks alot to John McClure for taking the time with this, 
> very stimulating :)  Some specific comments:
> 
> 1. Domain of labelling and documentation properties
> 
> The domain of the SKOS Core labelling properties 
> (skos:prefLabel, skos:hiddenLabel, skos:altLabel, 
> skos:prefSymbol, skos:altSymbol) has so far intentionally 
> been left as rdf:Resource so that these properties may be 
> used to describe anything at all.  
> 
> The domain of the SKOS Core documentation properties 
> (skos:definition, skos:scopeNote, skos:example, 
> skos:historyNote, skos:editorialNote ...) has also been left 
> as rdf:Resource.  Again this is deliberate, as especially 
> skos:definition and skos:example were envisaged as being 
> useful to describe e.g. classes and properties in an 
> ontology.  Commonly in current practice the rdfs:comment 
> property is used to give documentation describing the meaning 
> of e.g. a class or property in an ontology, but of course a 
> class or property may have many 'comments', and rdfs:comment 
> gets used in all sorts of ways - a more precise 'definition' 
> property is undeniably useful.  
> 
> For individuals in an ontology the semantics aren't so 
> obvious ... e.g. is it ok for a resource of type foaf:Person 
> to have a 'definition' ... ?  
> 
> Also bear in mind that currently if you use any of the SKOS 
> Core documentation properties you are  in OWL full, because 
> the range of SKOS Core documentation properties is completely 
> unspecified, and both literals and resources are allowed.  A 
> hack around to keep you in OWL DL would be for you to declare 
> locally that the documentation property you are using is 
> either an object property or a datatype property, depending 
> on how you are using it. 
> 
> 2. SKOS and topic maps
> 
> I hope that as soon as the RDFTM task force [1] has published 
> some RDF - TM mapping recommendations, we can go ahead and 
> publish a natural mapping from the classes/properties of SKOS 
> Core to some appropriate published topic map associations.  I 
> spoke to Richard Light recently about this, who has worked on 
> representing thesauri using topic maps.  Also Kal Ahmed lurks 
> on this list, and I suspect he has already published a number 
> of suitable associations from his 'topic map design patterns' 
> work.  Hopefully Kal and Richard will be able to help out 
> with that :)   
> 
> 3. Can a resource be both a skos:Concept and an rdfs:Class or 
> an rdf:Property?
> 
> This is something we've spent a lot of time discussing, but 
> haven't got a strong position on yet.  There are some subtle 
> issues, and a useful starting point is the short section in 
> the guide on 'relationship to RDFS/OWL ontologies', see [2] - 
> this requires careful reading.  
> 
> For recent discussion around proposed properties for mapping 
> between RDFS/OWL ontologies and SKOS concept schemes see [3] 
> and all subsequent in thread.  There's a lot of earlier stuff 
> too, search for 'denotes' in the subject line of mails in the 
> archive [4].
> 
> What I suggest we do is address this issue directly at the 
> next (3rd) review in 2-3 months time (the second review is 
> about to get underway).  I suggest that, for that review we 
> ask someone from the Ontology Engineering Patterns (OEP) task 
> force to be a reviewer, and we try to liase with OEP as much 
> as possible.
> 
> Until then, the 'play it safe' position is: assume that 
> skos:Concept is disjoint with rdfs:Class, owl:Class, and rdf:Property.
> 
> 4. Range of skos:subject
> 
> The property skos:subject inherits its meaning from its 
> super-property - dc:subject.  However, the range of the 
> dc:subject property can (and does) take anything and 
> everything.  The skos:subject property is primarily intended 
> as a property with the same semantics as dc:subject, but with 
> a more reliable range (i.e. you can expect to handle a 
> resource of type skos:Concept).
> 
> As others have pointed out, you can of course use e.g. OWL 
> classes in the range of skos:subject.  However, this will 
> lead to the inference that a resource is both of type 
> skos:Concept and owl:Class, and this leads you into the 
> undecided territory of point 3 above.
> 
> To 'play it safe', if you want to state that a class is the 
> subject of a document, use dc:subject, or your own refinement 
> of dc:subject; only use skos:subject with resources of type 
> skos:Concept, and assume that skos:Concept is disjoint with 
> rdfs:Class, owl:Class and rdf:Property.
> 
> 5. Broader/narrrower and class subsumption
> 
> I'm a bit confused with John's position here.  He states, 'I 
> am unable to detect any
> difference whatsoever between NT/BT and subclass/superclass 
> relations'.  This directly contradicts a large body of 
> consensus, and others have already disagreed with this 
> position.  The OEP part-whole note provides a nice 
> counter-example [5] in the section 'pattern 3'.
> 
> I'm going to leave it there for now, this email is long 
> enough already, thanks everyone for chipping in.
> 
> Cheers,
> 
> Al.
>  
> 
> [1] http://www.w3.org/2001/sw/BestPractices/RDFTM/
> [2] 
> http://www.w3.org/TR/2005/WD-swbp-skos-core-guide-20050510/#se
> cmodellingrdf
> [3] 
> http://lists.w3.org/Archives/Public/public-esw-thes/2005Jun/0002.html
> [4] 
> http://www.w3.org/Search/Mail/Public/search?keywords=&hdr-1-na
> me=subject&hdr-1-query=denotes&index-grp=Public__FULL&index-ty
> pe=t&type-index=public-esw-thes
> [5] 
> http://www.cs.man.ac.uk/~rector/swbp/simple-part-whole/simple-
> part-whole-relations-v0-2.html
> 
> > -----Original Message-----
> > From: public-esw-thes-request@w3.org
> > [mailto:public-esw-thes-request@w3.org]On Behalf Of Mark van Assem
> > Sent: 25 July 2005 10:55
> > To: John McClure
> > Cc: public-esw-thes@w3.org
> > Subject: Re: comment: WD 10 May 2005
> > 
> > 
> > 
> > 
> > Hi John,
> > 
> > Also thank you for your feedback, it is most instructive to see how 
> > someone with another perspective looks at SKOS.
> > 
> > > to associate an rdfs:Class through skos:subject with a 
> > resource. I am wondering,
> > > if an instance of rdfs:Class has a <skos:prefLabel>, then 
> > is the instance
> > > implicitly typed as a skos:Concept? I am thinking of the 
> > following triplets from
> > 
> > Nope, because <skos:prefLabel> has <rdfs:Resource> as domain 
> > (inherited from <rdfs:label>). If the domain of prefLabel was 
> > <skos:Concept> your statement is correct.
> > 
> > > Now, let me look for a moment at referencing rdfs:Class 
> > instances during
> > > construction of a ConceptSchema, the other side of the 
> > coin. Are the following
> > > triples recommended?
> > > 
> > > a:MyScheme	rdf:type		skos:ConceptScheme
> > > a:Animal	skos:inScheme		a:MyScheme
> > > a:Mammal	skos:inScheme 	a:MyScheme
> > 
> > Only if they are skos:Concepts.
> > 
> > > In any event, it seems to be a good idea to discuss in SKOS 
> > Core Guide how to
> > > reference instances of rdfs:Class as a resource subject and 
> > as a node in a
> > > concept schema.
> > 
> > I agree it would help for some people, but for others may be 
> > confusing 
> > and distracting from the main story. Am concerned that the 
> Guide gets 
> > "overloaded" with issues and becomes difficult to read.
> > 
> > Best,
> > Mark.
> > 
> > -- 
> >   Mark F.J. van Assem - Vrije Universiteit Amsterdam
> >         mark@cs.vu.nl - http://www.cs.vu.nl/~mark
> > 
> > 
> 
>

Received on Monday, 25 July 2005 16:53:22 UTC