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Re: Fw: No way to specify an RDF dataset of all the known named graphs

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 5 Apr 2007 14:20:35 -0500
Message-Id: <p06230914c23afc1ba535@[10.100.0.26]>
To: Lee Feigenbaum <feigenbl@us.ibm.com>
Cc: public-rdf-dawg@w3.org

>I'd like to know if anyone is motivated by Chimezie's comment suggesting
>that a FROM * and a FROM NAMED * be added to SPARQL to "provide an
>unambiguous way to specify a dataset which corresponds to all the known
>named graphs."
>
>I'm wary of adding this

Agreed. I don't even know what it could reasonably be understood to 
mean. Search through ALL the named graphs on the entire Web? (Why 
only the named graphs??)

Pat

>for a couple of reasons:
>
>1/ I can't imagine how such a construct would be defined such that it was
>any different from the implementation-defined state which currently exists
>when FROM and FROM NAMED are omitted. (And, therefore, the construct
>doesn't seem to add anything new or newly interoperable to the
>specification.)
>
>2/ Existing implementations solve this problem within the current bounds
>of SPARQL (see the IRC chat log cited for two examples)
>
>
>If you have a strong feeling one way or the other, please let it be known
>so that I can gauge whether the group has consensus (and either reply to
>Chimezie or slot this item on our teleconference agenda for next week).
>
>Lee
>
>
>----- Forwarded by Lee Feigenbaum/Cambridge/IBM on 04/05/2007 03:16 AM
>-----
>
>"Chimezie Ogbuji" <ogbujic@ccf.org>
>Sent by: public-rdf-dawg-comments-request@w3.org
>04/04/2007 05:05 PM
>Please respond to
>ogbujic@ccf.org
>
>
>To
>public-rdf-dawg-comments@w3.org
>cc
>
>Subject
>No way to specify an RDF dataset of all the known named graphs
>
>
>
>
>
>
>
>This was discussed in #swig
>(http://chatlogs.planetrdf.com/swig/2007-04-03.html#T20-38-01)
>
>SPARQL currently does not provide an unambiguous way to specify a
>dataset which corresponds to all the known named graphs.  The only way
>this can be done is to leave out FROM <..> and FROM NAMED <..>
>directives in the prolog (and from the protocol, for SPARQL services).
>The corresponding dataset in this case depends on the host application -
>not very consistent. The only other alternative is to explicitly
>enumerate the known universe in the prolog:
>
>FROM NAMED G1
>FROM NAMED G2
>...
>FROM NAMED GN
>
>This is not practical for a dynamic dataset.
>
>There is plenty of value in querying against the known universe
>consistently especially for applications which make use of a dataset as
>a named graph partition that can grow indefinitely.  Consider XPath
>2.0 / XQuery 1.0 which supports querying a collection of XML documents
>without having to explicitly enumerate all the XML documents in the
>collection.
>
>This is a very useful 'database-wide' query pattern which is well
>supported in document-management languages but not supported in SPARQL
>without assuming the implementation will consistently supply the dataset
>corresponding to all the known named graphs in persistence in the
>absence of any dataset directives in the prolog or at the protocol
>level.
>
>Other than OWA or CWA issues, I don't see why an explicit syntax for
>binding to such a dataset is not supported by SPARQL to provide a
>consistent way for applications to dispatch these kinds of queries.
>Such a syntax was suggested in the above conversation:
>
>FROM NAMED *
>
>[1] http://www.w3.org/TR/xquery-semantics/#sec_fn_doc_collection
>
>--
>Chimezie Ogbuji
>Lead Systems Analyst
>Thoracic and Cardiovascular Surgery
>Cleveland Clinic Foundation
>9500 Euclid Avenue/ W26
>Cleveland, Ohio 44195
>Office: (216)444-8593
>ogbujic@ccf.org
>
>
>
>
>
>
>Cleveland Clinic is ranked one of the top 3 hospitals in
>America by U.S.News & World Report. Visit us online at
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>
>===================================


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Received on Thursday, 5 April 2007 19:20:59 GMT

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