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Re: Meta-classes? (layered architecture)

From: pat hayes <phayes@ai.uwf.edu>
Date: Mon, 16 Oct 2000 15:18:46 -0500
Message-Id: <v0421010ab61111b8dfdd@[205.160.76.86]>
To: Ian Horrocks <horrocks@cs.man.ac.uk>
Cc: www-rdf-logic@w3.org
>On October 16, pat hayes writes:
> > >Firstly, my main point (with which I think Pat agrees) is that we
> > >should define a simple "base" language, and then extend it as
> > >necessary with -META -SECOND_ORDER or whatever.
> >
> > Yep, I think everyone agrees with this, more or less.
> >
> > >My particular worry was the potential confusion that is derived from
> > >building on top of RDFS, which is designed so as to be able to
> > >describe itself. For example, according to the specification,
> > >rdfs:Class is a type of rdfs:Class as well as being a subClassOf
> > >rdfs:Resource, which itself is a type of rdfs:Class. An rdf:Property
> > >is also a type of rdfs:Class.
> >
> > Ah, I may have been misreading this.  Maybe it is my turn to
> > demonstrate lamentable ignorance in public, but could you briefly
> > explain what the distinction is between being a type of and being a
> > subclass of? I assumed that the fact that rdfs:Class is a type of
> > rdfs:Class means that classes are a kind of class, which seemed
> > harmless since it is a tautology. (Perhaps I should understand the
> > first occurrence of 'rdfs:Class' here to be a mention rather than a
> > use?)
>
>My understanding is that for "type" we can read "instance of". e.g.,
>rdfs:subClassOf is an instance of rdf:Property, not a kind of
>rdf:Property.

Yes, sorry, that is what I meant by 'kind of', sloppy of me (as in 
"Pat Hayes is a kind of Englishman"). But now with this sense, where 
is the meta- ? After all, this isn't saying that the expression 
"subClassOf" is an instance of Property, right? It is talking about 
the thing (what I would call the relation of being a subclass of, 
although it might not be in a class labelled rdfs:Relation), not 
about the language.

Pat Hayes

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Received on Monday, 16 October 2000 16:15:44 GMT

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