- From: Sven Groppe <Sven.Groppe@deri.org>
- Date: Wed, 18 Jan 2006 12:33:50 +0100
- To: <public-rdf-dawg@w3.org>
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 Wednesday, 18 January 2006 11:37:25 UTC