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Comments on SPARQL 1.1 Query Language

From: David Booth <david@dbooth.org>
Date: Fri, 29 Jul 2011 14:32:06 -0400
To: public-rdf-dawg-comments <public-rdf-dawg-comments@w3.org>
Message-ID: <1311964326.2100.4577.camel@dbooth-laptop>

It is great to see this in Last Call!  Just a few things I noticed:

1. Section 8.3 
says: "whereas with MINUS, there is no shared variable between the first
part (?s ?p ?o) and the second (?x ?y ?z) so no bindings are
eliminated".  However, MINUS does not appear elsewhere in the TOC, and I
do not see any other direct explanation of the relevance of shared
variables between the first and second parts.  

I think I figured it out by looking at Sec 18.3 "Definition: Compatible
Mappings" in combination with the sec 18.4 "Definition: Minus".
Basically, if I understand correctly, *any* use of a variable in the
second part that does not appear in the first part likely amounts to a
user error because it can never remove any bindings involving that
variable, because the MINUS operator removes matching bindings and a
binding includes *both* variable names and their values.  I think it
would be helpful to state this (with the rationale) more prominently and

2. In Sec 18.3 "Definition: Compatible Mappings":
Two solution mappings μ1 and μ2 are compatible if, for every variable v
in dom(μ1) and in dom(μ2), μ1(v) = μ2(v).
that should be an "iff" instead of "if", right?  Or are there other ways
that μ1 and μ2 can be compatible?

"Operations may specify graphs to work with, or they may rely on a
default graph for that operation."
But don't operations use RDF Datasets, rather than graphs?

4. Regarding the typographical conventions that you use for conformance
When this document uses the words must, must not, should, should not,
may and recommended, and the words appear as emphasized text, they must
be interpreted as described in RFC 2119 [RFC2119].
As you can see in the excerpt quoted above, the typographical emphasis
of these keywords (i.e., bolding) is lost when the document is viewed as
plain text or copied and pasted as plain text.  This makes it more
difficult to quote and discuss portions of the specification precisely.
To ensure clarity, please make these keywords UPPER CASE (perhaps in
addition to being bold).

5. Typo:  s/righ hadn side/right hand side/


David Booth, Ph.D.

Opinions expressed herein are those of the author and do not necessarily
reflect those of his employer.
Received on Friday, 29 July 2011 18:32:32 UTC

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