[Crm-sig] non-existent objects

Alexander Dutton alexander.dutton at oucs.ox.ac.uk
Wed Nov 7 19:44:31 EET 2012


If you're willing to use OWL, I *think* you can do (in Turtle):

:statue a :Baseless .

:Baseless a owl:Class ;
   rdfs:subClassOf [
     a owl:Restriction ;
     owl:onProperty crm:P46_is_composed_of ;
     owl:allValuesFrom [
       a owl:Restriction ;
       owl:onProperty crm:P2_has_type ;
       owl:allValuesFrom [
         a owl:Restriction ;
         owl:onProperty rdf:value ;
         owl:hasValue "Basisplatte"
       ]
     ]
     owl:cardinality 0
   ] .

or:

:statue a [
   a owl:Restriction ;
   owl:onProperty crm:P46_is_composed_of ;
   owl:allValuesFrom [
     a owl:Restriction ;
     owl:onProperty crm:P2_has_type ;
     owl:allValuesFrom [
       a owl:Restriction ;
       owl:onProperty rdf:value ;
       owl:hasValue "Basisplatte"
     ]
   ]
   owl:cardinality 0
] .

If that doesn't work (I don't know whether using allValuesFrom and 
cardinality together is legal), it may be possible to use 
owl:complementOf to say that the statue is in the complement of the set 
of things that have bases. (http://www.w3.org/TR/owl-ref/#complementOf-def)

This is pretty much my first foray into OWL, so please forgive my 
inevitable wrongness.

Yours,

Alex

On 07/11/12 15:17, Wolfgang Schmidle wrote:
> Dear all,
>
> I am working on Arachne's Cidoc representation, and we came across a
> problem with non-existent objects and how to state their non-existence.
>
> A statue may be set up using e.g. a base or a plinth. In Arachne this
> can be specified in a data field called "Aufstellung" ("setup"). One can
> choose a description from a fixed list, for example "Basisplatte" or
> "Fußplatte/Plinthe". Now, we could model it as
>
>       E22 (the statue, without setup) P46i forms part of E22 (the statue
> plus the setup) P2 has type E55 Type e.g. "Basisplatte"
>
> but I am told that the setup should be seen as a part of the statue.
> Consequently we are modelling it as
>
>       E22 (the statue, including the setup) P46 is composed of E22 (the
> setup) P2 has type E55 Type e.g. "Basisplatte"
>
> However, Aufstellung may also have the value "ohne Basis" ("without
> base"). In this case the second E22 would denote a non-existent object,
> and its Type "ohne Basis" would state the non-existence of this object.
> (If the data field is left empty, we make no statement at all about the
> setup.)
>
> Is this the right way to model it? And is there a problem in RDF with an
> URI for a non-existent object?
>
> Additional question: Does Cidoc have an opinion about the the exact
> meaning of E22 P46 E22 P2 E55 "ohne Basis"? Let's take the word "sheep"
> as an example, where the singular and plural forms are the same: one
> sheep, two sheep. Is it comparable to A) "while most words have a plural
> morpheme, the particular word sheep has none", or B) "for systematic
> reasons we assume that all words have a plural morpheme, but for the
> particular word sheep it is null"?
>
> Thanks,
> Wolfgang
>
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