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Re: Review: SPARQL 1.1 Federated Extensions

From: Carlos Buil Aranda <cbuil@fi.upm.es>
Date: Tue, 01 Mar 2011 07:12:16 -0300
Message-ID: <4D6CC680.9040907@fi.upm.es>
To: Lee Feigenbaum <lee@thefigtrees.net>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>, Axel Polleres <axel.polleres@deri.org>
  On 28/02/2011 20:44, Lee Feigenbaum wrote:
> My original comment was asking how 4.1 and 4.3 are related. I'm still 
> not sure I understand; you seem to say that they are alternatives for 
> one another, but I don't see that.
>
> 4.1 deals with the translation from grammar to algebra and then 
> evaluation of algebra. I'm not sure what 4.3 is saying; for instance, 
> it uses ep(i) and then defines it, but I can't seem to make sense of 
> the use and definition of it.
>
> Also, whereas the evaluation algorithm in 4.1 (3.1 now) talks about 
> invoking the SPARQL protocol (which makes sense to me), the definition 
> in 4.3 (3.2 now) doesn't seem to say anything about how a pattern gets 
> evaluated against a remote endpoint. So as it stands now, if they 
> _are_ alternatives, I'd prefer to remove 3.2 and stick with 3.1, while 
> cleaning up 3.1 as per my comments in the original review.
3.1 and 3.2 are alternatives. What I say in 3.2 is that a pattern P is 
evaluated in the default graph. If that pattern P is of the form SERVICE 
i {P1} where i is a URI, then P1 is evaluated in the graph that is 
pointed by the function ep(i). What ep(i) does is to get the graph 
pointed by i. So in the end, the evaluation of SERVICE is the evaluation 
of its inner pattern in a graph pointed by i, like in the query 
document, but changing the default graph.

I do not know if explained myself? these are two proposals, in the end I 
will leave only one of them in final document.

Carlos
Received on Tuesday, 1 March 2011 10:51:45 GMT

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