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More minimalisic proposal than potentially bound (http://www.w3.org/2009/sparql/track/actions/329)

From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Date: Tue, 26 Oct 2010 17:55:21 +0100
Message-ID: <AANLkTim23KqSg8MMT_2A9ypGQN90QNPjXEzA1OtCgp1F@mail.gmail.com>
To: SPARQL Working Group <public-rdf-dawg@w3.org>
Hi all,
as I got an action (ACTION-329) today to come up with a definition for
what SELECT * actually means (possibly by rephrasing the potentially
bound text). Here's mmy attempt.

Ideally, I would just want to say:
If Q is a query with * in the select clause (SELECT *), then * is an
abbreviation for all variables that are in scope for Q.

This requires, however, that variable scope of a query is properly
defined and in the current Query 1.1 spec we just have:
4.1.3 Syntax for Query Variables
@@SPARQL 1.1 : need to modify the variable scope description to
reflect subqueries.

Thus, here's my attempt of defining scope, so that I can use the
definition for SELCT * as above:

Let Q be a query with group graph pattern G. The variables in scope
for Q, written scope(Q) are the variables in scope of G, written
scope(G). The variables in scope of a group graph pattern are
recursively defined as follows:
A group graph pattern G can either be a sub-select query (SubSelect
from the grammar) or a sub-group graph pattern (GroupGraphPatternSub
from the grammar). If G is a sub-group graph pattern, then G can
contain blocks of triples in addition to a non-triple graph pattern
(GraphPatternNotTriples in the grammar). Variables occurring in the
blocks of triples are in scope of G. If G contains a non-triple graph
pattern composed of one or more group graph patterns G1 to Gn, e.g.,
OPTIONAL G1 or G1 UNION G2, then variables in scope(Gi) for each 1 <=
i <= n are in scope for G. If G is a sub-select query with group graph
pattern G', then scope(G) = scope(G').

Any comments are welcome as usual.


Dr. Birte Glimm, Room 309
Computing Laboratory
Parks Road
United Kingdom
+44 (0)1865 283520
Received on Tuesday, 26 October 2010 16:55:54 UTC

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