Re: Safe Execution of Recursive Axioms + English

On Wednesday, October 1, 2003, at 04:46 PM, Adrian Walker wrote:
> We have some of the same concerns about RDF and OWL, and I have 
> occasionally questioned some of the folks preparing the W3C RDF 
> document about this.
>
> One thing that we have found that makes it easier to explore these 
> questions, is to have a mechanism that executes recursive axioms 
> safely and efficiently.  In addition, we assign an English meaning to 
> each predicate, to keep track of what we are doing.
>
> I'd be interested please in getting your set of axioms so far, plus 
> English comments where needed.
>
> If you can kindly send these, I will try rephrasing them in our 
> Internet Business Logic system.  Then, we can run them over 
> deliberately chosen tricky test examples to see what happens.  You and 
> your students will also be able to run them by pointing a browser to 
> our site if you wish.
>
> BTW, the system implements a model theory of stratified datalog 
> programs augmented with negation as failure, plus aggregation 
> predicates that support "bag", "set' and so forth.

This is soemthing I always wanted to ask: how comes that reasoning for 
a language like OWL (starting from OWL-lite itself) -- whose complexity 
has been proved to be EXPTIME-hard -- is going to be implemented with a 
polynomial language such as the datalog variant you're talking about? 
I've seen many implementations based on this idea (e.g., based on ECA 
rules), and I wonder whether there is something I'm missing.

cheers
--e.

Enrico Franconi                     - franconi@inf.unibz.it
Free University of Bozen-Bolzano    - http://www.inf.unibz.it/~franconi/
Faculty of Computer Science         - Phone: (+39) 0471-315-642
I-39100 Bozen-Bolzano BZ, Italy     - Fax:   (+39) 0471-315-649