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Re: rq25 aggregate functions

From: Andy Seaborne <andy.seaborne@talis.com>
Date: Mon, 21 Dec 2009 18:10:43 +0000
Message-ID: <4B2FBA23.6010303@talis.com>
To: Steve Harris <steve.harris@garlik.com>
CC: "public-rdf-dawg@w3.org Group" <public-rdf-dawg@w3.org>


On 20/12/2009 19:59, Steve Harris wrote:
> Hi all,
>
> I've just added the text on aggregate functions to
> http://www.w3.org/2009/sparql/docs/query-1.1/rq25.xml#aggregateFunctions
>
> The main new content is a new definition of Aggregation, to match the
> groups intentions for the use of aggregate functions, and definitions
> for COUNT, SUM, MIN, MAX, AVG, GROUP_CONCAT, and SAMPLE.
>
> The notation around “exp · μ'” in Aggregation is questionable, so if
> anyone has a better suggestion I'm all ears.
>
> I'm hoping to put the definitions for sub-select in rq25 on Monday.
>
> - Steve
>

[[
Definition: GroupConcat

The multiset of values passed as an argument is converted to a sequence S.

GroupConcat(S) = fn:string-join(S, " ")

@@ do we want space as the seperator? It's annoying in names for 
example. Other reasonable choices include ",", "\n", or "\t".
]]

All reasonable, none always right. I suggest that GroupConcat take an 
optional separator defaulting to a single space.

If the elements are "a" "b" "c"

CONCAT(?x) -> "a b c"
CONCAT(?x, "/") -> "a/b/c"

If the elements are integers 1 2 3

CONCAT(str(?x)+1) -> "2 3 4"
CONCAT(str(?x)+1, "+") -> "2+3+4"

	Andy
Received on Monday, 21 December 2009 18:11:08 GMT

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