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Re: "Unbound" in SPARQL

From: Andy Seaborne <andy.seaborne@talis.com>
Date: Tue, 17 Nov 2009 14:32:19 +0000
Message-ID: <4B02B3F3.1020805@talis.com>
To: SPARQL Working Group <public-rdf-dawg@w3.org>
We're mixing several things here:

1/ What happens with AS in SELECT when the expression evaluates to an error.
2/ What happens for aggregates of empty groups.
3/ What happens with errors in the expression being aggregated.

Another design to consider, is (case 1) that

   error AS ?x

leaves ?x unbound and (2) aggregates of empty sets are errors.

We then have what aggregates do about errors in their aggregate 
expression (case 3).  Skip or error.  I prefer skip because I want 
SUM(xsd:integer(?x)) to return something.

-----

To move forward, I think we should start to systematically look at use 
cases (and so get test cases).  We have been using examples to probe 
designs - now we should use them to define what matters most.  Let's not 
forget the simple cases.

Please could people contribute the cases they think matter most.  Does 
not have to a massive example: data/query/results are ideal but just 
query+description would be useful.

	Andy
Received on Tuesday, 17 November 2009 14:32:25 GMT

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