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Re: Today's Minutes / Publication Plan

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Wed, 25 Apr 2012 09:38:56 +0100
Message-ID: <4F97B820.1090709@epimorphics.com>
To: public-rdf-dawg@w3.org

On 25/04/12 09:11, Polleres, Axel wrote:
> I have a question on the discussion for BINDINGS:
> Was the proposal of SA-3 to allow BINDINGS also within subselects
> considered?
> If I understand it correctly, this would be implementable by
> changing one grammar rule
>   [8]   SubSelect   ::=   SelectClause WhereClause SolutionModifier
> to
>   [8]   SubSelect   ::=   SelectClause WhereClause SolutionModifier BindingsClause

Downside - you need to add a subquery in order to put BINDINGS inside a 
query i.e. overhead.

> I actually like this, since it seems to be quite a clean and simple
> way to address the issue:
> (i)   it makes BINDINGS available essentially anywhere
> (ii)  it still keeping BINDINGS "in spirit" at query level

BINDINGS don't really have any logical connection with query level as 
they are defined to be a join of they data table to the results of the 
graph pattern before select expressions and solution modifiers.

> (iii) it would allow to address the comments
> (iv)  it wouldn't cause any algebra changes, would it?

BINDINGS don't exist in the algebra :-) in the sense there is no 
"bindings" algebra operator.  They are become a data table that is 
joined in the usual way.  So just make the data table allowed at more 
places ...

> Thoughts?
> Best,
> Axel

Better: add BindingsClause to

[58]  GraphPatternNotTriples
    ::=  GroupOrUnionGraphPattern | OptionalGraphPattern | 
MinusGraphPattern | GraphGraphPattern | ServiceGraphPattern | Filter | 
Bind | BindingsClause

{ ?s ?p ?o BINDINGS ?p ?o { (:p 157) (:q 34.7) }

execution wise - happens after 'extend' (BIND) and before 'filter' (FILTER)

then its in subqueries and everywhere else.

Received on Wednesday, 25 April 2012 08:39:37 UTC

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