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SPARQL Semantics

From: Michael Schmidt <m.schmidt00@web.de>
Date: Mon, 11 Jun 2007 12:47:49 +0200
Message-Id: <127577031@web.de>
To: public-rdf-dawg-comments@w3.org


apologizes if this is not the right place to post my question. 

In "Semantics and Complexity of SPARQL" by Arenas, Gutierrez and Perez, a compositional and an operational semantics for the evaluation of SPARQL have been proposed.
A couple of months ago, I posted a question about the semantics of nested OPTIONALS to the ARQ mailing list (http://tech.groups.yahoo.com/group/jena-dev/message/25717), a topic that has been widely discusses in the W3C mailing list. The answer to my question was that Jena - as well as the W3C working draft at that time (http://www.w3.org/TR/2006/WD-rdf-sparql-query-20061004/), followed the operational semantics, which answered my question.

I just studied the new W3C SPARQL working draft semantics definition and it seems that, in meantime, the semantics changed and now follows the compositional approach. In spite of an extensive search in the W3C mailing list archive, I could not find any threads stating about this decision, but instead only threads containing general discussions and differences between both semantics. Have there been any public discussions on that topic, in particular why the semantics has been changed? And why did you use/propose the operational semantics before? I guess the main reason must have been not-commutativity of operator AND.

Any help would be appreciated,
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Received on Monday, 11 June 2007 14:13:24 UTC

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