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Re: Query Document Review

From: Steve Harris <steve.harris@garlik.com>
Date: Tue, 29 Mar 2011 13:15:37 +0100
Cc: W3C SPARQL Working Group <public-rdf-dawg@w3.org>
Message-Id: <DABA2BA3-46A3-4C39-8B68-10C60B948E86@garlik.com>
To: Matthew Perry <matthew.perry@oracle.com>
On 2011-03-15, at 13:05, Matthew Perry wrote:

> Hi,
> 
> My review the query document is below.

[snip]

> --- 11.7 ---
> It seems that unbound and error will be treated differently now (e.g. encountering a blank node during a sum() gives an error but encountering an unbound value has no effect). I recall that errors used to have the same effect as unbound.
> 
> If I understand correctly, these queries would have different results now whereas before they gave the same result.
> 
> SELECT (SUM(?X) + SUM(?Y) AS ?XY)
> WHERE { ?X :P ?Y }

So, SUM(?X) will be an error, meaning ?XY will be an error.

> SELECT SUM(?XY)
> WHERE { SELECT (?X + ?Y) AS ?XY
>        WHERE { ?X :P ?Y }
> }

I think that it will be the same, eval(?XY) will be an error, so SUM(?XY) will also be an error.

“ListEval((unbound), μ) = (error), as the evaluation of an unbound expression is an error.”
From §18.4, but it's stated informally in a number of places too.

Though, there was a typo in the definition of Sum() I've just fixed. Sum(3) was op:numeric-add(3, 1), which is clearly not right.

...

> Minor comments / typos:
> --- 1.1 ---
> [Sections => Section] 11 introduces the mechanism to group and aggregate results, which can [be] incorporated as subqueries as described in Section 12.

Thanks, fixed.

...

> --- 11.2 ---
> In order to calculate aggregate values for a solution, the solution is first divided into one or more groups, and [the the => the] aggregate value is calculated for each group.

Thanks again.

- Steve

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Received on Tuesday, 29 March 2011 12:16:13 GMT

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