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Re: Question on variable scope w.r.t. multiple optional blocks

From: Yoshio FUKUSHIGE <fuku@w3.org>
Date: Tue, 14 Dec 2004 20:41:27 +0900
Message-ID: <004001c4e1d1$d8de7a90$f1e41b85@steelball>
To: "Steve Harris" <S.W.Harris@ecs.soton.ac.uk>, <public-rdf-dawg@w3.org>

>> PREFIX foaf: <http://xmlns.com/foaf/0.1/>
>> SELECT ?name, ?nick
>> WHERE (?x foaf:name ?name)
>>          [(?x foaf:nick ?nick)
>>           (?x foaf:givenname ?nick)]
>>          [(?x foaf:nick ?nick)
>>           (?x  foaf:surname ?nick)]
>
> This would be quite confusing as you could get one solution with two
> different results for ?nick, using the current execution model. I think.

Oh...
Thank you, Steve,  for pointing it out.
Yes, you are right.

The optional conditions can be met at the same time, which slipped
from my mind...

Hmm, what can I do with my uneasiness...

It comes from the fact that whenever one adds a new clause to a query
under construction, one has to check if variables in the new clause 
confilict
with other variables in existing clauses.

Do you think it is a painful but unevitable and necessary task for users?
Or at least a realistic solution?

Only if we had some mechanism for explicitly denoting the scope of the 
variables!
Introducing such mechanism, however, would be very laborious...

Hmm

Yoshio
Received on Tuesday, 14 December 2004 11:41:31 GMT

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