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Re: What is an RDF Query?

From: Sandro Hawke <sandro@w3.org>
Date: Tue, 11 Sep 2001 16:04:09 -0400
Message-Id: <200109112004.f8BK49V05000@wadimousa.hawke.org>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
cc: phayes@ai.uwf.edu, www-rdf-rules@w3.org

> > I
> > suggest we ignore the syntax and simply say we're using an RDF
> > assertional graph (knowledge base) to convey the query (and its response).
> 
> Now I have a real problem.  Saying that we are using an RDF assertional
> graph carries along with it a lot of baggage, at least for human readers.
> Why not just say that we want to convey a query and a response, and try to
> figure out what sorts of queries and responses we want to query?
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^
I can't quite parse that, sorry.

> Yes, I know that syntax issues can cause lots of problems.  Yes, I know
> that it is possible to get into troubles by ignoring syntax issues.
> However, I think that it is much more likely to have lots of problems by
> considering meaning secondary to syntax than by considering syntax
> secondary to meaning.

I think understand.

We need something like four languages, right?

   1) language for asserting facts in a knowledge base
   2) language for adding inference rules to a knowledge
      base which allow it to infer new facts
   3) language for expressing a query of a knowledge base
   4) language in which the knowledge base replies to 
      a query.

I think I could come up with reasonably clear candidates for these
based on SQL, n3, prolog, some ascii versions of FOL, XML, etc.  But
the interesting part is that all four languages would have a lot in
common.   They'd all be something like

   1)  tell-fact(Expression facts)
   2)  tell-rule(Expression premise, Expression conclusion)
   3)  ask(Expression pattern)
   4)  binding map and/or Expression matched_pattern

with perhaps a few more details.  So the question is: what do we use as
the Expression language?

I lean towards RDF graphs as the expression language.  If we need a
character-based language, maybe N-Triples would be the clearest.

Then we have the question of what language & protocol we embed the
expression in -- this is where we say "tell-fact", "tell-rule", etc.
I suppose we might use SOAP for that, or a C-language API.   Or reify
the expression and use RDF again, but I'm sensing some resistance to
that.  :-)

     -- sandro
Received on Tuesday, 11 September 2001 16:11:10 GMT

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