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Re: definition of INDISTINCT

From: Jeen Broekstra <j.broekstra@tue.nl>
Date: Fri, 16 Mar 2007 17:39:25 +0100
Message-ID: <45FAC83D.3000500@tue.nl>
To: Eric Prud'hommeaux <eric@w3.org>
CC: public-rdf-dawg@w3.org


Alright, nitpicking a bit:

Eric Prud'hommeaux wrote:

> persuant to
>   ACTION: ericP to draft text about a LOOSE keyword and run it by w3
>   folks to see if we're abusing the "at risk" mechanism.
> I drafted this section. It was slightly more awkward to not have an
> ALL to lean on, but I think this is pretty well defined:
> 
> 9.4 INDISTINCT

When/where was this term introduced?

If we decide to add this, I think I would actually prefer LOOSE:
INDISTINCT suggests (to me at least) that it is the opposite of DISTINCT
(which it is not; it would even be acceptable to have the same behavior
as DISTINCT).

> While the DISTINCT modifier ensures that duplicate solutions are
> eliminated from the solution set, INDISTINCT simply permits them to be
> eliminated. The cardinality of any set of variable bindings (solution)
> in an INDISTINCT solution set at least one and not more than the

...*is* at least one...

> cardinality of the solution set with no DISTINCT or INDISTINCT
> modifier.

Perhaps better formulation would be to refer to the cardinality of the
solution set as prescribed by the algebra.

> For example, the query
> 
>   PREFIX foaf:    <http://xmlns.com/foaf/0.1/>
>   SELECT INDISTINCT ?name WHERE { ?x foaf:name ?name }
> 
> may have one, two (shown here) or three solutions:
>   name
>   "Alice"
>   "Alice"

Of course, this only holds for a dataset which holds at least three
solutions for Alice, you might want to make that more explicit in this
paragraph (referring back to the example dataset explicitly?).


Jeen
-- 
Dr. Jeen Broekstra                                          Den Dolech 2
Information Systems Group                                        HG 7.76
Department of Mathematics and Computer Science              P.O. Box 513
Technische Universiteit Eindhoven                      5600 MB Eindhoven
tel. +31 (0)40 247 36 86                                 The Netherlands
Received on Friday, 16 March 2007 16:42:16 GMT

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