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From: Jorge Pérez <jperez@ing.puc.cl>
Date: Tue, 5 Dec 2006 10:32:32 -0300 (CLST)
Message-ID: <51177.>
To: "Jeen Broekstra" <jeen.broekstra@aduna-software.com>, "Andy Seaborne" <andy.seaborne@hp.com>
Cc: public-rdf-dawg-comments@w3.org

Seaborne, Andy wrote:
>Jeen Broekstra wrote:
>> Defn: Diff
>> At this point we got a bit lost. I have difficulties grokking why the
>> definitions of Diff and LeftJoin include an expression as one of the
>> operands. I can't even comment on how to rephrase this as I simply don't
>> quite understand it (yet; I'll keep puzzling), but I would be much
>> happier with a more 'standard' definition of both operators that just
>> takes two operands, and then later on introduce the filter expression
>> (if needed).
>> At the very least I could use some clarification here :)
> http://lists.w3.org/Archives/Public/public-rdf-dawg/2006OctDec/0115.html
> http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2006Oct/0030.html
> http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2006Oct/0031.html

Only to state my point again:

I think that the non-standard definition of Diff and LeftJoin having an
expression as one of the arguments, only to provide users with a *one
level* conditional OPT, is a bad design decision, and will raise a lot of
problems in understanding and implementations in the future. How you
explain users that they can make a *one level* conditional OPT and cannot
make a *two level* conditional OPT? and cannot make somethig similar with
other operators?


- jorge
Received on Tuesday, 5 December 2006 13:32:53 UTC

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