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Re: paper on RDF querying relevant to DAWG (and to current discussions)

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 29 Mar 2006 11:46:00 -0500 (EST)
Message-Id: <20060329.114600.95188695.pfps@research.bell-labs.com>
To: tessaris@inf.unibz.it
Cc: public-rdf-dawg-comments@w3.org, public-rdf-dawg@w3.org

I wasn't asking for a survey/comparison, just a pointer.

peter


From: Sergio Tessaris <tessaris@inf.unibz.it>
Subject: Re: paper on RDF querying relevant to DAWG (and to current discussions)
Date: Wed, 29 Mar 2006 14:34:00 +0200

> 
> On 29 Mar 2006, at 14:07, Peter F. Patel-Schneider wrote:
> 
> >
> > I am a bit confused as to just what is being proposed here.
> >
> > I would have have been satisfied with a simple acknowledgment in  
> > the SPARQL
> > documents that the work I mentioned is related to SPARQL.  I don't  
> > see any
> > reference to such an acknowledgment.
> 
> Peter, I'm not sure whether the SPARQL document is the right place  
> for a survey/comparison of different approaches to the problem of  
> querying RDF(S) documents. If this is the case I think that there are  
> other relevant references which didn't find their way into the document.
> 
> The technical contents of Mendelzon's work have been brought to the  
> attention of the WG. Moreover, changes to the initial SPARQL draft  
> have been influenced by this work. It could be worth pointing it out  
> by means of references in the WG web pages.
> 
> I reckon that a specific document on the relation of SPARQL with  
> other query languages would be a useful contribution to the Semantic  
> Web community; but I see it as a complementary document to the  
> current SPARQL document.
> 
> Cheers,
> --sergio
> 
> >
> > However, in the end, this is not a technical isues, and thus I am  
> > not going
> > to make a fuss over it, particularly as I am making a fuss over  
> > technical
> > issues.  If the DAWG feels that it does not need to reference prior
> > closely-related work, I'm not in a position to prevent it from so  
> > doing.
> >
> > What makes the lack of reference to the work by Mendelzon even more  
> > jarring
> > to me is the inclusion of at least one reference (CBD) that has  
> > less to do
> > with the design of SPARQL than Mendelzon's work does.  There is even a
> > reference in the reference list (VCARD) that is not pointed to from  
> > the
> > body of the document.
> >
> > peter
> >
> > From: Sergio Tessaris <tessaris@inf.unibz.it>
> > Subject: [OK?] paper on RDF querying relevant to DAWG (and to  
> > current discussions)
> > Date: Wed, 29 Mar 2006 09:18:46 +0200
> >
> >> ---
> >> Please respond indicating whether you are or are not satisfied with
> >> this response. If you are, you can help our issue tracking system by
> >> prefixing the subject of your response with [CLOSED] (where this
> >> subject has [OK?]).
> >> ---
> >>
> >> The mentioned papers indeed present a coherent and well defined
> >> framework for the problem of querying RDF graphs. However, the query
> >> language proposed is somewhat restricted and doesn't fulfil the
> >> requirements for SPARQL (see [UCNR]).
> >>
> >> Moreover, in its basic definitions is not far away from the current
> >> version of the SPARQL document. In fact, a tableau as defined in the
> >> paper can be seen as a CONSTRUCT query containing a single graph
> >> pattern, where the head and the body of the tableau are the template
> >> and the graph pattern respectively. The semantic definitions in
> >> Section 4.2 of the paper are substantially equivalent to those of the
> >> latest SPARQL document. In particular, the definition of pre-answer
> >> correspond to the SPARQL answer set (provided that valuations are
> >> considered instead of graphs).
> >>
> >> Note that the notion of answers to a query is defined in terms of
> >> subgraph homomorphism; so, although it works well with RDF(S) has
> >> problems in scaling up with more expressive ontology languages (see
> >> owlDisjunction  issue at http://www.w3.org/2001/sw/DataAccess/
> >> issues#owlDisjunction).
> >>
> >> In the paper, two different semantics are considered for the result
> >> of a query as the combination of the graphs in the so called pre-
> >> answer, namely the union or the (RDF) merge. In SPARQL, the CONSTRUCT
> >> operator adopts the merge semantics.
> >>
> >> Constraints, as introduced in the paper correspond to the FILTER
> >> operator in SPARQL.
> >>
> >> The paper introduces the idea of premises for a query, which can be
> >> easily handled by SPARQL by means of the ability of querying multiple
> >> graphs.
> >>
> >>
> >> Regards,
> >> --sergio
> >>
> >> [UCNR] RDF Data Access Use Cases and Requirements , K. Clark, Editor,
> >> W3C Working Draft. Latest version available at http://www.w3.org/TR/
> >> rdf-dawg-uc/ .
> >>
> >> On Sunday 18 September 2005 17:02, Peter F. Patel-Schneider wrote:
> >>> Hi:
> >>>
> >>> A couple of days ago I came across the following paper:
> >>>
> >>> 	Foundations of Semantic Web Databases.
> >>> 	Claudio Gutierrez, Carlos Hurtado - Universidad de Chile;
> >>> 	Alberto Mendelzon - University of Toronto.
> >>> 	PODS 2004, pp. 95 - 106.
> >>>
> >>> The paper refers to an earlier paper, "Formal aspects of querying  
> >>> RDF
> >>> databases", "for the case with no rdfs vocabulary" that was
> >>> presented at
> >>> the First International Workshop on Semantic Web and Databases co-
> >>> located
> >>> with VLDB held at Berlin, Germany, September 7-8, 2003.
> >>>
> >>> These papers have a very good set of definitions for querying RDF.
> >>> Although the second, more developed, paper concentrates on the case
> >>> of RDFS
> >>> its solutions appear to be directly relevant to the Data Access  
> >>> Query
> >>> Working Group.
> >>>
> >>>
> >>> Peter F. Patel-Schneider
> >>> Bell Labs Research
> >>
> >> -- 
> >> --------------------------------------------------------------------- 
> >> --
> >> Sergio Tessaris, Assistant Professor        Faculty of Computer  
> >> Science
> >> e-mail: tessaris@inf.unibz.it          Free University of Bozen- 
> >> Bolzano
> >> http://www.inf.unibz.it/~tessaris                   Piazza  
> >> Domenicani 3
> >> tel: +39 0471 016 125 (fax 009)                    39100 Bolzano,  
> >> Italy
> >
> 
> Sergio Tessaris, Assistant Professor        Faculty of Computer Science
> e-mail: tessaris@inf.unibz.it          Free University of Bozen-Bolzano
> http://www.inf.unibz.it/~tessaris                   Piazza Domenicani 3
> tel: +39 0471 016 125 (fax 009)                    39100 Bolzano, Italy
> 
> 
Received on Wednesday, 29 March 2006 16:46:29 GMT

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