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Re: Innovation, community and queries

From: Arnold deVos <adv@langdale.com.au>
Date: Tue, 4 Jun 2002 09:25:57 +1000
Message-ID: <004501c20b56$08dc6630$ea01a8c0@cockatoo>
To: "Patrick Stickler" <patrick.stickler@nokia.com>, "Danny Ayers" <danny666@virgilio.it>, "Uche Ogbuji" <uche.ogbuji@fourthought.com>
Cc: "Seaborne, Andy" <Andy_Seaborne@hplb.hpl.hp.com>, "ext Thomas B. Passin" <tpassin@comcast.net>, "RDF Interest" <www-rdf-interest@w3.org>

Thanks for the comments.

----- Original Message -----
From: "Patrick Stickler" <patrick.stickler@nokia.com>
> > [1]  http://www.langdale.com.au/RDF/NexusQueryLanguage.pdf
> This seems more like query in XML than in RDF. Perhaps I missed something.

Oops, the presentation is intended for a different audience and is given in
terms of a non-striped syntax.  Sorry for the confusion - I should have
prefaced this reference with an explanation.  The template and call elements
translate to properties in a query graph.  Internally, the implementation
accepts two graphs (the query and the context) and produces XML.

> The template priority looks interesting. Examples of its use in practice
> would be nice to see.

Template priority is a feature that occasionally gets used.  It is analogous
to the same feature in XSLT and disambiguates when more than one template
would otherwise match.  Consider a general template (say for matchning
serializing rdfs:label's) and a special case template (say for handling
rdf:label's of rdfs:Class's).  The latter would be given higher priority.

> > [2] http://www.langdale.com.au/RDF/DAML-Query.html
> This is clearly RDF query in RDF (well DAML ;-)
> I find the partitioning of the query into the select and from portions
> a bit cumbersome -- in the same way that trying to view an XML instance
> stored in an RDBMS is cumbersome.

Yes it looks like a throwback to RDBMS :-)

>  You have to kinda keep track of
> the target description on several levels -- first specify the properties
> of relevance in the select statements and then describe, be means of
> a class no less, the actual value constraints for those properties.

No, the from section constrains the subjects of the result statements and is
independent of of the select section which constrains the predicates of the
result statements.

> And don't the property restrictions make the property select statements
> redundant?

Well, the property restictions are part of the definition of a set of
subjects.  The select properties determine what statements about those
subjects will appear in the results.

> I think that the average RDF user (or even the average advanced RDF
> but not DAML user) will not warm too much to such a representation.
> Still, DAML die-hards may feel right at home with it ;-)

Probably needs work.  I am still looking for something to use in my
application (alluded to in the introduction)....

 - Arnold
Received on Monday, 3 June 2002 19:24:20 UTC

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