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[Danny Ayers]
> >
> > [Danny Ayers]
> > > ...
> > > CGs and RDF have a lot in common. Taking the main points of the
abstract
> > > syntax for CGs in the ISO standard [1] it's possible to map
> > across fairly
> > > directly to aspects of RDF (this is a 2 minute, first shot attempt) :
> > >
> > > 6.3 Conceptual Relation - Statement (/Property)
> >
> > Disagree. "In a conceptual graph, the boxes are called concepts, and
the
> > circles are called conceptual relations." (Sowa 2000, p476). RDF has no
> > conceptual relations. They have to be simulated, most likely with
bnodes.
>
> Hmm, I would have thought that most of the time CG conceptual relations
> would have mapped directly to RDF properties :
>
In general, CG conceptual relations are n-ary, not binary. Simulating an
relation with valence of 5, say, by using a bnode could be done, but there
is no way, even with OWL, so far as I can see, to declare a restriction on
the number and types of predicates that the bnode must have to match the
valence of the CG relation.
> From the CG tutorial [1] :
>
> A cat is on a mat.
>
> CG version (approx) :
>
> [Cat]->-(On)->-[Mat]
>
From CG examples at http://users.bestweb.net/~sowa/cg/cgexamp.htm#Ex_4
"A person is between a rock and a hard place}" - a relation of arity 3
[Person]<-(Betw)-
<-1-[Rock]
<-2-[Place]->(Attr)->[Hard].You need to convert the (Betw)
relation to a bnode to simulate this.
> > > 6.7 Referent - Object (of statement)
> >
> > Disagree. A referent is essential an identifier (Sowa, p 424).
>
> Ok, I must have misinterpreted that - URIref instead then.
>
Nope, a referent can have a complex structure (includng wildcards and
variable names). I suspect that a compex referent would be impractical to
represent by a URI.
> Yep, RDF itself is essentialy just e-c. But it's possible through the use
of
> RDFS to create terms outside the core, and then give those terms more than
> what's found in base level RDF. e.g. let's have :
>
> xmldev:not rdfs:subClassOf rdf:Property
>
> and with a bit of verbal fluff we have negation.
>
Wrong model - not() is a monadic relation, not binary. RDF can have no
monadic relations, even with [name your favorite] layered on top.
In RDF it is painful at best to refer to some particular GC-like context (an
arbitrary subgraph), because subgraphs are not identifiable. You have to
invent something equivalent to rdf:Statement, but more general. Unpleasant.
Anyway, the degree of extension to RDF needed would be significant. You
need negation and quantification, at least.
Cheers,
Tom P
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