Intro + question

Dear members of the DAWG working group,
 
I am an employee of the Digital Enterprise Research Institute
(DERI), which has a big focus on the Semantic Web
and contributes already to other W3C working groups like
RIF, at the University of Innsbruck.
See below for my business contact.
 
Originally, I came from the database community. My
topic of my Doctorate is "XML Query Reformulation
for XPath, XSLT and XQuery" (ISBN 3-933893-24-0).
 
I hope I can contribute to the DAWG working group
regarding my background and although the working group
seems to be nearly finished.
 
I have a question concerning the
"SPARQL Query Language for RDF
W3C Working Draft 23 November 2005".
I think it is similar to the remarks of
http://www.w3.org/2001/sw/DataAccess/issues#cascadedQueries,
but I apologize if I oversee further discussions.

I am of the opinion that is important
to support nested queries. Nested queries
are important if you want e.g. support views,
which plays is a key point for integrating
heterogeneous sources.

I would expect that the production
[9]   DatasetClause   ::=   'FROM' ( DefaultGraphClause | NamedGraphClause )


would allow to query also the result of
a ConstructQuery, i.e. 

[9]   DatasetClause   ::=   'FROM' ( DefaultGraphClause | NamedGraphClause |
ConstructQuery) 

Simple Example:

PREFIX foaf:    <http://xmlns.com/foaf/0.1/>
PREFIX vcard:   <http://www.w3.org/2001/vcard-rdf/3.0#>

SELECT ?mbox
FROM
	CONSTRUCT   { <http://example.org/person#Alice> vcard:FN ?name }
	WHERE       { ?x foaf:name ?name }
WHERE
  { ?x foaf:name "Johnny Lee Outlaw" .
    ?x foaf:mbox ?mbox }
 
Note that this is a simple example and that for
other views in real integration scenarios
of course more complicated CONSTRUCT queries
would occur.

I apologize again if I oversee something
in the specification that allows some kind
of nested queries or if there was a discussion
with the decision not allowing nested queries.
In the latter case, I would be interested
in the arguments not to support nested
queries as I cannot imagine reasonable
arguments (except implementation effort).
 
Cheers,
Sven.
_______________________________________________
 
Dr. Sven Groppe
 University of Innsbruck
 Institute of Computer Science
 Digital Enterprise Research Institute (DERI)
 EMail: Sven.Groppe@deri.org
 Phone: +43 512 507 6424
 Fax:   +43 512 507 9872

Received on Thursday, 19 January 2006 16:00:58 UTC