Vocab AND Ontology?

Ed Shaya eshaya at umd.edu
Mon Sep 24 08:55:54 PDT 2007 

Bernard,
	Well, I have to agree to the point that OWL and SKOS have different 
aims.  The aim of OWL is nothing less than expressing knowledge in 
computer readable form.  SKOS is aimed at relating vocabulary terms, 
which one has to admit is a subset of knowledge.
Therefore, you can easily incorporate the skos terms into an OWL 
ontology if you like.  I provide an OWL skos ontology below.
So now you can have within OWL skos:related, broader, narrower, and the 
various types of notes (description, historyNote, etc...), Concept and 
subjectOf property. And keep rigorous rdf:subClass.  And make use of all 
of the OWL tools and utilities.  In fact most of these "concepts" 
(including Concept) were already in our ontology 
http://archive.astro.umd.edu/ont/index.html at the top level, 
Science.owl), but I am happy to hand these over to the skos namespace as 
they are not really science terms.

One should be careful though to use subClassOf if the thing is really a 
subClass and narrower if it is not a subClassOf but a related term 
within the scope of the broader term.

As for the specific example of white dwarf and Chandrasekhar limit (CL). 
  In OWL you can restrict the WhiteDwarf to have Mass hasValue (maxValue 
hasValue CL).  The CL is an instance of MassLimit.  MassLimit are a 
subClassOf  Mass.  Measurements have property sci:of, which allows 
restriction: "CL of WhiteDwarf".  The question then is, do you bother to 
mention that CL and WhiteDwarf are also SKOS:related?

Ed

skos.owl
<rdf:RDF xmlns="http://www.w3.org/TR/swbp-skos-core-guide#"
      xml:base="http://www.w3.org/TR/swbp-skos-core-guide"
      xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
      xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
      xmlns:owl="http://www.w3.org/2002/07/owl#"
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
     <owl:Ontology rdf:about=""/>
     <owl:ObjectProperty rdf:ID="broader"/>
     <owl:DatatypeProperty rdf:ID="changeNote">
         <rdfs:subPropertyOf rdf:resource="#note"/>
     </owl:DatatypeProperty>
     <owl:Class rdf:ID="Concept"/>
     <owl:DatatypeProperty rdf:ID="definition">
         <rdfs:subPropertyOf rdf:resource="#note"/>
     </owl:DatatypeProperty>
     <owl:DatatypeProperty rdf:ID="editorialNote">
         <rdfs:subPropertyOf rdf:resource="#note"/>
     </owl:DatatypeProperty>
     <owl:DatatypeProperty rdf:ID="example">
         <rdfs:subPropertyOf rdf:resource="#note"/>
     </owl:DatatypeProperty>
     <owl:DatatypeProperty rdf:ID="historyNote">
         <rdfs:subPropertyOf rdf:resource="#note"/>
     </owl:DatatypeProperty>
     <owl:ObjectProperty rdf:ID="isPrimarySubject">
         <owl:inverseOf rdf:resource="#primarySubject"/>
         <rdfs:subPropertyOf rdf:resource="#isSubjectOf"/>
     </owl:ObjectProperty>
     <owl:ObjectProperty rdf:ID="isSubjectOf">
         <rdfs:domain rdf:resource="#Concept"/>
         <owl:inverseOf rdf:resource="#subject"/>
     </owl:ObjectProperty>
     <owl:ObjectProperty rdf:ID="narrower"/>
     <owl:DatatypeProperty rdf:ID="note">
         <rdfs:range rdf:resource="&xsd;string"/>
     </owl:DatatypeProperty>
     <owl:ObjectProperty rdf:ID="primarySubject">
         <owl:inverseOf rdf:resource="#isPrimarySubject"/>
         <rdfs:subPropertyOf rdf:resource="#subject"/>
     </owl:ObjectProperty>
     <owl:ObjectProperty rdf:ID="related"/>
     <owl:DatatypeProperty rdf:ID="scopeNote">
         <rdfs:subPropertyOf rdf:resource="#note"/>
     </owl:DatatypeProperty>
     <owl:ObjectProperty rdf:ID="subject">
         <rdfs:range rdf:resource="#Concept"/>
         <owl:inverseOf rdf:resource="#isSubjectOf"/>
     </owl:ObjectProperty>
     <owl:ObjectProperty rdf:ID="subjectIndicator">
         <rdf:type rdf:resource="&owl;InverseFunctionalProperty"/>
         <rdfs:domain rdf:resource="#Concept"/>
     </owl:ObjectProperty>
</rdf:RDF>


Bernard Vatant wrote:
> Tony, and all
> 
> On the OWL vs SKOS debate, I would like to quickly stress again a point 
> I tried to make before
> http://www.ivoa.net/forum/semantics/0709/0362.htm
> ... but which was maybe blurred by other points in this verbose message 
> ;-) .
> 
> SKOS is not a "low-level-semantics" OWL, because SKOS and OWL have not 
> the same functional aims. Again, re-read above message for more details.
> Choosing either one of those representations, or both, should not be 
> based on feasibility/complexity of representation, but on functional 
> objectives. Let me take an example illustrated in both Ed's Star 
> ontology and IAU Thesaurus, the "White Dwarf Star" concept
> - If you are a documentalist want to index/search/retrieve 
> documents/data about "White Dwarf Stars", a SKOS concept "White Dwarf 
> Stars" is what you need, and the position of this concept in a Concept 
> Scheme hierarchy, and its association with other concepts such as 
> "Chandrasekhar Limit".
> - If you want to classify objects, find them using logical inference, an 
> OWL class "White Dwarf Star" is what you need, with its necessary 
> conditions, attached properties, position in a subsumption tree etc.
> 
> If you want both uses, you need both representations, BUT : *you can't 
> expect to automatically and safely transform one representation into the 
> other automatically*.
> - From SKOS to OWL : not every concept defined in a SKOS concept scheme, 
> and used for indexing/search/retrieval makes sense as a class in a OWL 
> ontology. See the "cosmology example" in my previous message.
> - From OWL to SKOS : only concepts represented as classes would be 
> available for indexing, so you would have to add indexing concepts which 
> were not present as OW classes.
> 
> Look at White Dwarf in IAU Thesaurus and in star ontology. In the former 
> you find the related concept "Chandrasekhar Limit", which makes perfect 
> sense for indexing, because there is a lot of litterature for which 
> Chandrasekar limit is a relevant indexing concept, and even the primary 
> topic. But you don't find "Chandrasekhar Limit" at all in the star 
> ontology, although it's a very pertinent concept in stellar 
> astrophysics, but there again it's perfectly normal because this concept 
> does not fit in as a class, nor even as an individual or property value. 
> One can imagine a formal definition of the white darf class including 
> indirectly this concept by putting a constraint on the mass (although 
> this is tricky in OWL), but you get the picture.
> 
> This example again to illustrate why I'm concerned about any methodology 
> based on : let's do SKOS first, and then we will transform into OWL, or 
> the other way round.
> 
> Bernard
> 
> Tony Linde a écrit :
>>> Correspondingly, the OWL is
>>> trivially produced from either format if you're interested (some of
>>> us are definitely NOT).
>>>     
>>
>> This seems the core question, Rick (whatever the starting point and I 
>> agree
>> that the IAU Thesaurus seems a good one from my naive pov): do we produce
>> the SV in OWL and derive the SKOS or produce it in SKOS and derive the 
>> OWL?
>>
>> I'd still plump for the former for the following reasons:
>>
>> a. either approach seems, at the outset, to involve little cost 
>> (though I'd
>> still assert that the availability of Protege and other ontology tools 
>> make
>> this a cheaper route);
>>
>> b. any extensions to the ontology will break the link between 
>> vocabulary and
>> ontology since the extensions could not be derived from the vocab so we
>> could well end up with divergent terms meaning the same thing;
>>
>> c. it seems that no matter how the ontology (with vocab included) is
>> extended, we can still derive the vocabulary providing we mandate that 
>> vocab
>> terms use the classes and relationships specified.
>>
>> This is a fairly simplistic view, I know. Can anyone show any 
>> methodological
>> or technical problem with this approach (I don't think Rick pointed 
>> out any
>> real problems with the OWL-based approach: what ontological baggage might
>> cause problems)?
>>
>> And this is still only my view - others will have their own position 
>> on the
>> question above.
>>
>> T.
>>
>>  
>>> -----Original Message-----
>>> From: owner-semantics at eso.org [mailto:owner-semantics at eso.org] On
>>> Behalf Of Frederic V. Hessman
>>> Sent: 24 September 2007 10:14
>>> To: semantics at ivoa.net
>>> Subject: Re: Vocab AND Ontology?
>>> ...
>>>     
>>
>>
>>
>>   
> 
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