Re: I have a trouble with The RDF Model

>At 09:44 AM 11/27/00 -0600, pat hayes wrote:
>>The domain of a model theory, more or less by definition of the 
>>term "model theory", is the expressions of the language (or perhaps 
>>more exactly, the parsings of those expressions according to the 
>>syntactic rules of the language.)
>I'm not sure I'd know a model theory if it leapt up and bit me, but 
>that's a useful start for me.  What would you say is the "range" of 
>a model theory?

I'm glad you asked. The range is the interpretations. Thats what a 
model theory does: it defines (a mathematical model of) what counts 
as an interpretation of the language, and gives rules for how to 
interpret the expressions of the language in such an interpretation. 
(Other names for interpretations are 'possible world', 'set of 
circumstances' 'state of affairs' and 'model of the world'.) Exactly 
what counts as an interpretation, speaking now mathematically, 
depends on the language; more intricate langauges require more 
complicated notions of 'interpretation'. Propositional logic requires 
simply an assignment of truth-values to the basic proposition 
letters. First-order relational logic requires a set over which the 
quantifiers range, and denotations defined over this set for all the 
names and relation names in the language. Programming languages have 
traditionally required functional domains obeying certain fixpoint 
properties. Modal logics require more complicated interpretations 
with multiple domains linked by accessibility relations, and so on. 
'Ontology' lanugages like DAML, which essentially describe a 
heirarchy but don't say anything much about it, seem to require only 
some sets with some relations between them as an interpretation, as 
in Peter Patel-Schneider's OIL semantics. Right now Im not yet sure 
what RDF really needs, but Im working on it.

>>So I repeat: are you saying that the 'at' assertions are part of RDF, or not?
>I'd say not, but that it is possible to _model_ the 'at' assertions in RDF.

The trouble with that answer is, I really do not know what it means. 
What sense of 'model' are you using? Do you mean it is possible to 
*describe* them in RDF? Or that it is possible to *simulate* them in 
RDF? Or that they are some kind of assertional *extension* to RDF? Or 
*axioms written in RDF syntax*? Any help would be appreciated.

Pat Hayes

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Received on Wednesday, 29 November 2000 17:38:42 UTC