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Re: SPARQL Update 1.1 review part1

From: Paul Gearon <gearon@ieee.org>
Date: Mon, 7 Feb 2011 22:38:56 -0500
Message-ID: <AANLkTikDGy9dttN8M+SOTpSLUYnFNPXD81nCiKEX26TZ@mail.gmail.com>
To: Axel Polleres <axel.polleres@deri.org>
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>, Alexandre Passant <Alexandre.Passant@deri.org>
Alex originally dealt with Axe's review, but I am going over it now.

I have a question about Axel's point 27:

On Thu, Sep 30, 2010 at 6:10 PM, Axel Polleres <axel.polleres@deri.org> wrote:
> 27)
> "Using a new blank node in a delete template will lead to nothing being deleted, as the new blank node cannot match anything that already exists."
> this seems to contradict resolution http://www.w3.org/2009/sparql/meeting/2010-03-09#resolution_2
> I haven't seen any resolution overriding that, but I might have missed that. Even if we decided to override that resolution, it is not entirely clear to me what "new" blank node means exactly here.

Here is a copy of the resolution that Alex mentions:

"Blank nodes in DELETE templates act as "wild cards", effectively as
variables bound to all RDF terms; the same blank node cannot be used
in the WHERE clause and the template, or in multiple BGPs"

Unfortunately, I was not at this meeting, and it's something that I
missed when the minutes came around. I find this to be an unfortunate
decision, as it effectively makes the template part of the WHERE
clause. To illustrate, the operation:

DELETE { [] :p ?x }
WHERE { ?x :q :z }

Is going to be effectively the same as:

DELETE { ?a :p ?x }
WHERE { ?x :q :z . ?a ?p ?o }

(ignoring the existence of the ?p and ?o)

I'm really uncomfortable with this. Is it set in stone?

Paul Gearon
Received on Tuesday, 8 February 2011 03:39:29 UTC

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