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Re: Unexpected DISTINCT?

From: Richard Newman <rnewman@franz.com>
Date: Tue, 27 Mar 2007 14:22:01 -0700
Message-Id: <4102B4E5-11CB-438E-BA4F-D29B7B5AEA5E@franz.com>
Cc: "Lee Feigenbaum" <feigenbl@us.ibm.com>, public-rdf-dawg-comments@w3.org
To: "Andrew Newman" <andrewfnewman@gmail.com>

>> In the absence of the DISTINCT or REDUCED keywords, the specification
>> gives a precise cardinality for the solutions that appear in the  
>> solution
>> sequence.
> Does this mean the DISTINCT part of the SPARQL specification is
> incorrect? It says:
> "The solution sequence with no DISTINCT or REDUCED modifier may
> include duplicate solutions"
> http://www.w3.org/TR/rdf-sparql-query/#modDistinct

It's probably more accurate to say "might" rather than "may", in that  
it depends on the data. If run against a certain dataset:

- DISTINCT is well-defined (no duplicates)
- neither DISTINCT nor REDUCED: well-defined (duplicates if the data  
includes duplicates)
- REDUCED: implementation-defined (might have duplicates).


P.S., thank you for your response, Lee. I hadn't spotted REDUCED before.
Received on Tuesday, 27 March 2007 21:22:13 UTC

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