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RE: SeRQL an RDF rule language: scoping Rules vs Query in W3C work

From: Wolf Siberski <siberski@learninglab.de>
Date: Thu, 6 Nov 2003 09:14:49 +0100
To: <www-rdf-rules@w3.org>
Message-ID: <002c01c3a43e$0c6d6790$ac574b82@ravel>

Dan Brickley wrote:
> * Bill de hÓra <dehora@eircom.net> [2003-11-05 18:12+0000]
> > 
> > Patrick Stickler wrote:
> > >
> > >I agree with Jeen's points below.
> > >
> > >To add my own 2 cents, I'd also like to see query and rules solutions
> > >for RDF expressed *in* RDF. 
> > 
> > I'm not sure how that would be done in RDF as it stands, given its
> > expressive power, but it seems like a nice thing to have.
> What you might end up with here is an RDF *description* of a query-related 
> data structure. Maybe handy for testcase-style interop, but pretty ugly
> to read and think about. 

As Edutella was mentioned: In Edutella, a datalog syntax (with N3 elements)
is used for 'human-readable/writable' queries, but each query can as well 
be represented as RDF graph. Of course, in RDF/XML syntax queries are pretty 
unreadable. But we can store them in triple stores, search for queries, etc., 
and this comes quite handy. 

> Closest you can get and still be pretty is a kind of query-by-example, 
> with bNodes for variables, perhaps decorated with variable names in a 
> well-known namespace. Such RDF/XML would never be taken assertionally 
> but used to ask questions. I think Edutella have something in 
> this vein. 

Our query-by-example syntax allows only a very restricted form of queries, 
and internally the queries are converted into a rule-based form anyway.

> Sorry I'm in a rush or I'd do the googling for links. 

You can find the language description at http://edutella.jxta.org/spec/qel.html.
Section 5 contains the RDF syntax.

Regarding the original question: IMHO we should try to tackle the query
and rule level jointly and specify the language semantics based on a
rule language approach. Then we can define different syntaxes which
serve different usage needs, e.g. a SQL-like syntax to pose queries without
rules, a Prolog-/datalog-like syntax to pose queries which need rules
to express them, an RDF representation to store and reason about queries, etc.

Received on Thursday, 6 November 2003 04:34:28 UTC

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