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SELECT to involve expressions [was: Comments list comments]

From: Dan Connolly <connolly@w3.org>
Date: Mon, 21 Mar 2005 10:53:29 -0600
To: "Seaborne, Andy" <andy.seaborne@hp.com>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-Id: <1111424009.8271.425.camel@localhost>

On Mon, 2005-03-21 at 16:04 +0000, Seaborne, Andy wrote:
> Matters arising from the comments list:
> 
> 
> 1/ SELECT to involve expressions
> 
> SQL allows constants and expressions in explicit projections (SQL SELECT in 
> other words)
> 
>    SELECT ?x "constant" ...
>    SELECT ?x (?x+?y) ...
> 
> Combined with nested SELECTs and UNIONs, we would have a way to tag which branch 
> of a union a solution came from.  This can already be done using different 
> variables in each branch.
> 
> This would require access to results by column number (or aliases which are not 
> required by SQL) and so have impact on the results format.
> 
> At the moment, SPARQL UNION is defined without the explicit SELECT projection 
> and is a graph pattern operator.  There is no no assignment of values - it's not 
> possible to return RDF terms that are not in the graph or a dataset label.

let's use technical, rather than (or in addition to) process keywords
in the subject.

[2nd issue to follow separately...]

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Monday, 21 March 2005 16:53:32 GMT

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