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Re: Converting VALUES to SPARQL algebra

From: james anderson <james@dydra.com>
Date: Mon, 2 Mar 2015 12:18:27 +0000
Message-ID: <0000014bda6c540c-20a08003-7d8f-4a4e-afbb-44534e5d0c44-000000@eu-west-1.amazonses.com>
To: public-sparql-dev@w3.org
good afternoon;

On 2015-03-02, at 12:53, Joachim Van Herwegen <Joachim.VanHerwegen@ugent.be> wrote:

> My problem is actually more of a syntax problem: I want to know what the exact SPARQL algebra syntax is when converting one of these queries, I understand what they are supposed to do but I don't know how to write it in algebra format.
> As mentioned before, I find examples using table/row, but I don't think these are part of the spec?

as well-intentioned as 18.2 (http://www.w3.org/TR/2013/REC-sparql11-query-20130321/#sparqlQuery) of the recommendation may be, it does not specify a notation for the algebra, as such, just translation a process which targets certain algebra expressions from respective sparql expressions.
given which, it is no surprise that some gaps would exist, leaving 18.2.4.3 with a description of the intent, but lacking the notation.

if there were a normative notation for the abstract algebra, that would be very nice.
as matters stand, there are gaps.
my recollection is that the circumstances surrounding aggregation, ordering and limits was particularly intriguing.
in such cases - even though our own notation for the algebra is not identical with arq’s, that implementation has been invaluable in filling in for the recommendation.

best regards, from berlin,
---
james anderson | james@dydra.com | http://dydra.com
Received on Monday, 2 March 2015 12:18:56 UTC

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