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Comment on: rq25

From: Olivier Corby <Olivier.Corby@sophia.inria.fr>
Date: Mon, 21 Dec 2009 11:19:26 +0100
Message-ID: <4B2F4BAE.2020606@sophia.inria.fr>
To: SPARQL Working Group <public-rdf-dawg@w3.org>
I have some comments on rq25.


The structure of this doucment

8 Negation - Testing for the absence of a pattern

I am not really happy that the EXISTS and NOT EXISTS pattern can be used 
in a filter.
Should this happen, can it be used with the boolean operators: &&   ||   !

This sentence is not clear:

In the case where the NOT EXISTS pattern is used, it applies only to 
variables defined earlier in the pattern.

In the example given, the ?name variable is not defined earlier in the 

?person rdf:type  foaf:Person .
NOT EXISTS { ?person foaf:name ?name }

This sentence is odd:

Translation of a filter expression in that uses NOT EXISTS or EXIST in a 
FILTER proceeds as for all other filter operations.

The example is given twice :

 { ?s rdf:type <t>
   NOT EXISTS { ?s <p> ?v }
  ?s :p ?o


{ ?s rdf:type <t>

   NOT EXISTS { ?s <p> ?v }

   ?s :p ?o
9 Aggregate Functions - Projecting values over groups of solutions

In presence of aggregate function, is it possible to select a variable ?

For example:

select ?doc  min(?price) as ?min where {
   ?doc :price ?price
12.1.2 SELECT expressions

   in the SELCT clause
Question about this sentence:

The new variable is introduced using the keyword AS; it must not already 
be potentially bound.

What about this case with subquery:

select * where {
?doc :price ?price
{select ?x (?p + 10) as ?price where {
   ?x :price ?p}

The syntax error arises for use of a variable *in as* the target of AS 
... AS ?x) when the variable is used inside the WHERE clause of the SELECT.

Is it an error if the variable is used in  ORDER BY, GROUP BY ?
and in HAVING (in the case of aggregate) ?

What about distinct, does it select distinct values of price ?

select distinct price(?doc) as ?price where {
    ?doc :author ?a

Received on Monday, 21 December 2009 10:20:02 UTC

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