W3C home > Mailing lists > Public > public-swd-wg@w3.org > March 2009

Re: [SKOS] SKOS ontology sanity-check? An attempt at creating OWL2 axioms for SKOS

From: Ivan Herman <ivan@w3.org>
Date: Fri, 20 Mar 2009 14:28:39 +0100
Message-ID: <49C39A07.2010006@w3.org>
To: Antoine Isaac <aisaac@few.vu.nl>
CC: SWD WG <public-swd-wg@w3.org>
Antoine,

a heroic effort with a moving target:-)

Just a few pointers that may help:

- the editor's draft of the Syntax document for OWL 2[1] includes all
the examples in RDF, too. There is a set of buttons at the beginning of
the document where you can select which syntax you want to see for the
examples. Maybe that helps...

- it is indeed true that the core functional syntax for OWL 2 does not
define the usage of property disjointness for annotation properties.
However, in the RDF compatible semantics of OWL 2 (essentially, OWL 2
Full), propertyDisjointWith is defined on _any_ property, ie, it
provides the necessary semantics for disjoint annotation properties, too.

Disjointness of annotation properties as a requirement never came to the
OWL 2 group, to be honest...

- as an answer to one of the LC comments, the RDF encoding of property
chains have changed. In the final version of OWL 2 the encoding of your
axiom should be (in turtle):

skos:prefLabel
   owl:propertyChainAxiom (skos:prefLabel skos:literalForm).


Cheers

Ivan


[1] http://www.w3.org/2007/OWL/wiki/Syntax
[2] http://www.w3.org/2007/OWL/wiki/RDF-Based_Semantics

Antoine Isaac wrote:
> Hi,
> 
> I have given a try at creating OWL 2 axioms for representating our
> non-formally stated axioms in skos.rdf and [1] for skos-xl.rdf [2], see
> below.
> 
> I found it in fact really more difficult than planned, and the lack of
> RDF/XML examples in OWL2 is really an obstacle.
> 
> Anyway, it seems a good idea to already be aware right now of the issues
> that we could have later...
> 
> I hope this will help,
> 
> Antoine
> 
> ==================
> 
>    S12.  The rdfs:range of each of skos:prefLabel, skos:altLabel and
> skos:hiddenLabel is the class of RDF plain literals.
> 
> At first sight this axiom could represented using rdf:Text. [3] reads:
>> The datatype identified by the URI
>> http://www.w3.org/1999/02/22-rdf-syntax-ns#text (abbreviated rdf:text)
>> allows for the representation of internationalized text strings. In
>> addition to the RIF and OWL specifications, this datatype is expected
>> to supersede RDF's plain literals with language tags
> 
> However, I would not recommend to use it until the "expectations" have
> been met, and RDF plain literals indeed been superseded.
> 
> ==================
> 
>    S13. skos:prefLabel, skos:altLabel and skos:hiddenLabel are pairwise
> disjoint
> 
> Here is a first try at an RDF/XML representation of this axiom:
> 
>    <owl:ObjectProperty rdf:about="#prefLabel">
>        <owl:propertyDisjointWith rdf:resource="#altLabel"/>
>        <owl:propertyDisjointWith rdf:resource="#hiddenLabel"/>
>    </owl:ObjectProperty>
>    <owl:ObjectProperty rdf:about="#altLabel">
>        <owl:propertyDisjointWith rdf:resource="#hiddenLabel"/>
>    </owl:ObjectProperty>
> 
> 
> However I'm not sure this would be ok, as [4] hints at applying it
> either to object properties or datatype properties, but says nothing on
> annotation properties...
> 
> Indeed I tried to create the axiom using Protégé 4. It assumed that
> prefLabel, altLabel and hiddenLabel were instances of DatatypeProperty,
> and represented my axioms as:
>        <owl:disjointObjectProperties rdf:resource="#hiddenLabel"/>
> But apparently this owl:disjointObjectProperties construct does not
> exist in the RDF mapping at [5]!
> 
> Note that OWL 2 also allows for group declaration of disjoint
> properties. But given that we only have three disjoint properties, and
> that group disjointness seems cumbersome to represent in RDF syntax (it
> requires using owl:AllDisjointProperties, and an owl:members which
> intuitively conflicts with rdf:member the same way as our own
> skos:member does :-/ ), I'd recommend to keep to the simple construct.
> 
> 
> ==================
> 
>  S14. A resource has no more than one value of skos:prefLabel per
> language tag.
> 
> This cannot be expressed.
> 
> =================
> 
>  S27. skos:related is disjoint with skos:broaderTransitive
> 
> With the same caveats as for S13 (my Protégé had used
> owl:disjointObjectProperties), we can represent this axiom by:
> 
>    <owl:ObjectProperty rdf:about="#related">
>        <owl:propertyDisjointWith rdf:resource="#broaderTransitive"/>
>    </owl:ObjectProperty>
> 
> =================
> 
>    S36. For any resource, every item in the list given as the value of the
>      skos:memberList property is also a value of the skos:member property
> 
> This axiom cannot be represented, unless we first introduce an auxiliary
> propery that allows a direct access to the object of the rdf:rest
> statement in the definition of the member list.
> 
> =================
> 
>    S46. skos:exactMatch is disjoint with each of the properties
> skos:broadMatch and skos:relatedMatch.
> 
> With the same caveats as for S13, we can represent this axiom by:
> 
>    <owl:ObjectProperty rdf:about="#exactMatch">
>        <owl:propertyDisjointWith rdf:resource="#broadMatch"/>
>        <owl:propertyDisjointWith rdf:resource="#relatedMatch"/>
>    </owl:ObjectProperty>
> 
> 
> ============ SKOS-XL
> 
>    S51. The range of skosxl:literalForm is the class of RDF plain literals.
> 
> Cf S12.
> 
> =================
> 
>    S55. If C skosxl:prefLabel L and L skosxl:literalForm V, then X
> skos:prefLabel V.
> 
>    <rdf:Description>
>        <rdfs:subPropertyOf
> rdf:resource="http://www.w3.org/2004/02/skos/core#prefLabel"/>
>        <owl:propertyChain rdf:parseType="Collection">
>            <rdf:Description
> rdf:about="http://www.w3.org/2008/05/skos-xl#prefLabel"/>
>            <rdf:Description
> rdf:about="http://www.w3.org/2008/05/skos-xl#literalForm"/>
>        </owl:propertyChain>
>    </rdf:Description>
> 
> 
> 
> =================
> 
>    S56. If C skosxl:altLabel L and L skosxl:literalForm V, then X
> skos:altLabel V.
> 
>    <rdf:Description>
>        <rdfs:subPropertyOf
> rdf:resource="http://www.w3.org/2004/02/skos/core#altLabel"/>
>        <owl:propertyChain rdf:parseType="Collection">
>            <rdf:Description
> rdf:about="http://www.w3.org/2008/05/skos-xl#altLabel"/>
>            <rdf:Description
> rdf:about="http://www.w3.org/2008/05/skos-xl#literalForm"/>
>        </owl:propertyChain>
>    </rdf:Description>
> 
> 
> =================
> 
>    S57. If C skosxl:hiddenLabel L and L skosxl:literalForm V, then C
> skos:hiddenLabel V.
> 
>    <rdf:Description>
>        <rdfs:subPropertyOf
> rdf:resource="http://www.w3.org/2004/02/skos/core#hiddenLabel"/>
>        <owl:propertyChain rdf:parseType="Collection">
>            <rdf:Description
> rdf:about="http://www.w3.org/2008/05/skos-xl#hiddenLabel"/>
>            <rdf:Description
> rdf:about="http://www.w3.org/2008/05/skos-xl#literalForm"/>
>        </owl:propertyChain>
>    </rdf:Description>
> 
> ==============
> 
> 
> [1] http://www.w3.org/2006/07/SWD/SKOS/reference/20081001/skos.rdf
> [2] http://www.w3.org/2006/07/SWD/SKOS/reference/20081001/skos-xl.rdf
> [3] http://www.w3.org/TR/2008/WD-rdf-text-20081202/
> [4] http://www.w3.org/TR/2008/WD-owl2-quick-reference-20081202/
> [5] http://www.w3.org/TR/2008/WD-owl2-mapping-to-rdf-20081202/
> 
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf



Received on Friday, 20 March 2009 13:28:29 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Friday, 20 March 2009 13:28:30 GMT