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SPARQL: Editorial comments on Last Call WD

From: Ivan Herman <ivan@w3.org>
Date: Tue, 02 Aug 2005 16:49:28 +0200
Message-ID: <42EF87F8.4050005@w3.org>
To: public-rdf-dawg-comments@w3.org
Dear all,


all these comments (maybe with the exception of the last one) are small scale
editorial, a.k.a. hair-splitting:-) and is more for readability.

Ivan

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IRI misuse issue (Section 2.1)

I wonder whether the text on IRI misuse (Section 2.1, Query Term Syntax) should
really be part of a normative text. Some other W3C recommendations separate in
the text the 'normative' and 'informative' parts; if this was done in SPARQL,
this would certainly be an 'informative' paragraph... However, SPARQL does not
do that separation, ie, everything is normative.

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Wrong link text (Section 2.2)

Section 2.2 second paragraph after the first definition says: [3987, sec. 3.1].
I presume '3987' should refer to a RFC 3987 or, more appropriately, to reference
no. 19

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"Matching dataset DS" (Section 2.4)

The formal definition in 2.4 says: "S is a pattern solution for GP matching
dataset DS". There is no formal definition of what "matching" means at that
point (it is defined in 2.5 later, ie, a 'post-definition'...). I think moving
the sententence defining matching from 2.5 to here is better and clearer.

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Editorial issue on Group Graph Pattern (Section 4.1)

Reading the spec from start to end, and getting to 4.1 gives a stange impression
on groups. The whole section seems to argue that, in fact, groups are just
syntactic sugar because they can be flattened, and that is all the section says.
If my understanding is correct, groups become important when combined with, say,
Optionals within the groups, but this comes much later in the document. For the
sake of readability some sort of an explanation would be welcome here.

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Unbound variables in a solution

Section 4.2 says: "Solutions to graph patterns do not necessarily have to have
every variable bound in every solution that causes a graph pattern to be
matched. In particular, the OPTIONAL and UNION graph patterns can lead to query
results where a variable may be bound in some solutions, but not in others."

With my English I could interpret this sentence as follows: I could have a graph
pattern match *without* OPTIONAL or UNION where not all variables are bound.
That is probably not the intention, and would be in contradiction with the
remark at the very end of 2.6 which says "This is a simple, conjunctive graph
pattern match, and all the variables used in the query pattern must be bound in
every solution."

I think it should be clearly stated somewhere in the document that *unless*
OPTIONAL and UNION is used, all variables MUST have a binding in a solution.

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Matching Literals in lexical or value space (Section 3.1)

Section 3.1 does not say whether matching datatype literals is done in lexical
or in value space. Ie, if the data is:

:a :b "10.00000000"^^xsd:double

and the query is

WHERE { ?x :b "10.0"^^xsd:double }

Do I get ":a" as a solution or not?

SPARQL may be oblivious to this and it may depend on the RDF data store. If that
data store does RDFS-D entailement, than the existence of the the

:a :b "10.0"^^xsd:double

is inferred and the query will return ":a". If not, there is no match. However,
something should be said in the SPARQL document (note that section 11, Testing
Values, does not answer this because it refers to FILTERS-s only.)

[The float case is relatively simple, but more complex issues arise, for
example, with XML Literals]


--

Ivan Herman
W3C Communications Team, Head of Offices
C/o W3C Benelux Office at CWI, Kruislaan 413
1098SJ Amsterdam, The Netherlands
tel: +31-20-5924163; mobile: +31-641044153;
URL: http://www.w3.org/People/Ivan/

Received on Tuesday, 2 August 2005 14:49:23 GMT

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