Re: Semantics, in particular DAML+OIL semantics

Ian, thank for posting these to rdf-logic. It would be good to have a 
discussion on the issue of different approaches to providing a semantics 
for the languages of the semantic web.

I agree with you that for the purpose of providing a semantics for any 
one particular language, a "native" model theory, i.e., one that maps 
sets of expressions in that language to satisfying interpretations, is 
best in terms of perspicuity and pedagogy. So, I agree that it is 
important that RDF, OWL, ... be given native model theories.

I would however argue that in the context of the Semantic Web, we are 
dealing with a situation that is quite different from when we are 
developing a single, standalone language. We are developing a set of 
languages, that are supposed to work together, i.e., wffs on the SW may 
include constructs from multiple of these languages. More so, these 
languages are expected to be layered on top of each other. Now, one can 
argue, as some have, that this charter is ill-concieved, but for the 
purpose of this email, I will assume that as a given. Further, I am also 
not going to get into a discussion of whether RDF/OWL should include 
certain features. That is the topic of another email.

The problem, in this context, with relying solely on model theories, is 
that this does not give us a tool for providing a semantics for 
expressions that mix constructs from  different languages. That is a 
rather severe limitation of relying solely on model theories.  Axiomatic 
approaches on the other hand, by mapping everything into a common 
language, do enable us to provide a semantics for such "mixed expressions".

I am not advocating that we abandon model theoretic approaches in favour 
of the other approach. I would like to see both. Which of course brings 
us to the issue of making sure that both are saying the same thing. 
Fortunately, since the whole semantics game grounds out in 
interpretations, I believe we can have a formal model of what it means 
for these two approaches to say the same thing. Pat Hayes and I have 
taken a stab at this in our Lbase document.

I look forward to your reactions.

thank you

Guha

Received on Monday, 12 August 2002 13:17:25 UTC