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

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Thu, 06 Nov 2003 16:00:11 +0200
To: ext Dan Brickley <danbri@w3.org>, Bill de hÓra <dehora@eircom.net>
Cc: <www-rdf-rules@w3.org>
Message-ID: <BBD0208B.4664%patrick.stickler@nokia.com>

On 2003-11-05 20:18, "ext Dan Brickley" <danbri@w3.org> 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. I believe DAML Query works this way. My
> understanding of XQuery btw is that they started out with an XML syntax
> but now mostly focus on the non-XML syntax, since it is vastly more
> usable. My hunch is that RDF Query might go the same way...

Again, "in RDF" does not have to mean "in RDF/XML".

In fact we support N3 for RDFQ queries, which results in very easy
to write, concise, queries which are nevertheless expressed fully
in RDF. 

E.g.

Match all resources where the dct:modified value is less than one week
ago (i.e. all resources modified in the last week):

[:target [dct:modified [:le :one-week-ago]]].


> 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.

Right. One is defining a template to be matched against asserted statements
in the graph.

> I think Edutella have something in this vein. Sorry
> I'm in a rush or I'd do the googling for links. Also this approach
> doesn't allow blanks for property names, since RDF/XML doesn't allow
> that.

That is true, though I've yet to see a compelling query associated
with a real-world use case that does not specify a property.

Patrick
Received on Thursday, 6 November 2003 09:02:38 UTC

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