- From: Steve Harris <steve.harris@garlik.com>
- Date: Mon, 19 Apr 2010 22:43:24 +0100
- To: Andy Seaborne <andy.seaborne@talis.com>
- Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
+1 to being able to compose queries like that. It matches how I build complex queries.
- Steve
On 2010-04-19, at 09:19, Andy Seaborne wrote:
> In SPARQL 1.0 the following query is illegal because the label "a" is used twice in different BGPs.
>
> PREFIX : <http://example/>
>
> SELECT *
> {
> _:a :p ?x .
> OPTIONAL { _:a :w ?y }
> }
>
> We have a choice in SPARQL 1.1 Query as to whether this scoping rule applies to the query or the SELECT statement.
>
> In SPARQL 1.1, we now have nested SELECTs. It is convenient to be able to paste one SELECT, having got it working, into another query. Having to check labels stops a simple cut&paste of we decide the scope is the query.
>
> PREFIX : <http://example/>
>
> SELECT *
> {
> _:a :p ?x .
> { SELECT * { _:a :p ?y } }
> }
>
> I suggest that we clarify blank node scoping rule to apply to one SELECT statement, not the whole query, making the SPARQL 1.1 query above legal.
>
> Analogous things happen with unprojected variables:
>
> PREFIX : <http://example/>
>
> SELECT *
> {
> :a :p ?x .
> { SELECT (COUNT(*) AS ?C) { :a :q ?x } }
> }
>
> The two ?x are unrelated - they never meet at an operation that causes a join over them.
>
> CONSTRUCTs already allow labels to be used twice.
>
> CONSTRUCT { _:a :p ?x } WHERE { _:a :q ?x }
>
> Andy
>
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Received on Monday, 19 April 2010 21:43:54 UTC