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DISTINCTness of literals

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Mon, 25 Sep 2006 11:22:10 +0100
Message-ID: <4517ADD2.4070204@hp.com>
To: RDF Data Access Working Group <public-rdf-dawg@w3.org>

We left open what to do about literals of the same value in DISTINCT results.

I propose that term-distinct apply to literals, and not a form of value-distinct.

SPARQL is defined for simple entailment anyway so for this entailment regime 
it would be term-distinct for literals.  I propose that rq24 only talk about this.

Some considerations:

1/  It's terms that are returned, not values, when encoded into the result 
set.  But which term should be returned if two literals are value-distinct and 
not term-distinct?



The SPARQL test suite is based on RDF graph equality [1] which uses term 
equality for literals.

2/ XPath/XQuery Functions&Operators [2] allows numeric type promotion - but 
XML schema datatypes does not and double/float/decimal have different value 
spaces.  See [3].

"1.3"^^xsd:double != "1.3"^^decimal

I've checked in a test [4] for literal distinctness.


[1] http://www.w3.org/TR/rdf-concepts/#section-graph-equality
[2] http://www.w3.org/TR/xpath20/#promotion
[3] http://www.w3.org/TR/swbp-xsch-datatypes/
[4] http://www.w3.org/2001/sw/DataAccess/tests/data/Distinct/
Received on Monday, 25 September 2006 10:22:32 UTC

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