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Re: Draft response to BT-1

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Fri, 07 Oct 2011 15:26:32 +0100
Message-ID: <4E8F0C18.1020301@epimorphics.com>
To: public-rdf-dawg@w3.org


On 07/10/11 13:15, Steve Harris wrote:
> Comment:
> http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2011Aug/0000.html
>
> Draft response:
> http://www.w3.org/2009/sparql/wiki/CommentResponse:BT-1
>
> - Steve
>

The example is a bit more complicated because it involved aggregation 
and select expressions.

An error in an aggregate is not trapped specifically by the aggregate - 
it's an error.  In the example it's because the select expression that 
you get an unbound.

SELECT ( 1/0 AS ?x ) {}

is:

-----
| x |
=====
|   |
-----

this then explains the second point: ?c can be bound if AVG is an error 
because the AVG error is handled in SELECT expressions.

SELECT
    ( COALESCE(SUM(?a),"error") AS ?x )
    (SUM(?a) AS ?y )
{ BIND ("abc" AS ?a) }

==>

---------------
| x       | y |
===============
| "error" |   |
---------------

and then HAVING( aggregate error ) is just like a FILTER and error.

	Andy
Received on Friday, 7 October 2011 14:27:05 GMT

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