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SPARQL Query: subqueries

From: Olivier Corby <Olivier.Corby@sophia.inria.fr>
Date: Mon, 10 May 2010 13:53:19 +0200
Message-ID: <4BE7F3AF.9080801@sophia.inria.fr>
To: SPARQL Working Group <public-rdf-dawg@w3.org>
I think we may say a word about the effect of from and from named on a 
subquery, do from and from named apply to the subquery:

select *
from <uri1>
from named <uri2>
where {
{select * where {
  graph ?g {?x ?p ?y} ?y ?q ?z
}}
}


We  may also say a word on the effect of a graph graph pattern on a 
subquery:


select *
from named <uri2>
where {
graph ?g {
   {select * where {?x ?p ?y}}
}
}

I also wonder why "It is an error to reuse variable names both inside 
and outside a subquery when the variable is not projected from the 
subquery."
Such variables may be local variables with no incidence with the outside 
of the query. In particular, if we build a complex query with copy-paste 
of existing queries, there may be duplicate variable names.


Olivier
Received on Monday, 10 May 2010 11:53:57 GMT

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