- From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Date: Wed, 29 Mar 2006 11:46:00 -0500 (EST)
- 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 UTC