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Re: [Fwd: Comments on SPARQL from the XML Query and the XSL WGs]

From: Dan Connolly <connolly@w3.org>
Date: Thu, 10 Nov 2005 17:00:07 -0600
To: andy.seaborne@hp.com
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-Id: <1131663608.12579.147.camel@dirk>

On Tue, 2005-11-08 at 18:24 +0000, Seaborne, Andy wrote:
> Proposed reply:
[...]
>  > 1. If RDF triples are stored in a relational database (in-memory
>  > databases are available now) then SQL can be used to query them.  SQL
>  > has much more power and is a well-known language, but there are a
>  > couple of features peculiar to RDF that are unique in SPARQL such as
>  > the OPTIONAL clause.  An analysis of how much overlap there is between
>  > SQL and SPARQL would be useful.
> 
> There are already implementations that based on SQL so useful experience 
> reports are beginning to appear and will continue to appear throughout this 
> phase and the CR process.

I just discvoered this; seems worth citing in our reply...


A relational algebra for SPARQL


Cyganiak, Richard

HPL-2005-170 
20050928 
External

Keyword(s): RDF; semantic web; databases; query

Abstract: The SPARQL query language for RDF provides Semantic Web
developers with a powerful tool to extract information from large
datasets. This report describes a transformation from SPARQL into the
relational algebra, an abstract intermediate language for the expression
and analysis of queries. This makes existing work on query planning and
optimization available to SPARQL implementors. A further translation
into SQL is outlined, and mismatches between SPARQL semantics and the
relational approach are discussed.

http://www.hpl.hp.com/techreports/2005/HPL-2005-170.html

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Thursday, 10 November 2005 23:00:14 GMT

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