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[CLOSED] Re: SPARQL: Editorial comments on Last Call WD [OK?]

From: Ivan Herman <ivan@w3.org>
Date: Thu, 10 Nov 2005 05:35:59 +0100
Message-ID: <4372CE2F.5010101@w3.org>
To: andy.seaborne@hp.com
Cc: public-rdf-dawg-comments@w3.org
Andy,

thanks very much. It is all fine with me.

Ivan

-------- Original Message --------
From: "Seaborne, Andy" <andy.seaborne@hp.com>
To: Ivan Herman <ivan@w3.org>
CC: public-rdf-dawg-comments@w3.org
Subject: Re:SPARQL: Editorial comments on Last Call WD [OK?]
Date: 7/11/2005 16:29

>
>
> Ivan Herman wrote:
>
>> 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,
>
> Thank you for the comments.
>
>>
>> Ivan
>>
>> --------------------------------------------------------------------
>>
>> 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.
>
>
> The text in this section has been reworked as part of various comments.
>
> The text on multiple IRIs that may have the same appearance (I take it
> this is
> what you mean by "misuse") has been placed in a separate Security
> Considerations section.
>
>>
>> --------------------------------------------------------------------
>>
>>
>> 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
>
>
> Fixed
>
>>
>> --------------------------------------------------------------------
>>
>> "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.
>
>
> "matching" is used in all the different graph pattern types so I have
> mentioned this as covered in various sections to follow this one.  As
> solutions are used in matching there is a cirularity that is hard to
> avoid and
> still indicate what solutions are used for.
>
>>
>> --------------------------------------------------------------------
>>
>> 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.
>
>
> I have removed the use of "syntactically" which was confusing and moved
> that
> sentence so it is not first.
>
>>
>> --------------------------------------------------------------------
>>
>> 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.
>
>
> I agree it's not very clear - a variable not mentioned in a basic
> pattern will
> remain untouched (bound/unbound), and this is significant because
> OPTIONAL and
> UNIONS are combining patterns which are themselves basic patterns.
>
> Changed to:
>
> [[
> Solutions to graph patterns do not necessarily have to have every variable
> bound in every solution. SPARQL query patterns are built up from basic
> patterns which do associate RDF terms with each variable mentioned in the
> pattern; OPTIONAL and UNION graph patterns can lead to query results
> where a
> variable may be bound in some solutions, but not in others.
> ]]
>
>>
>> --------------------------------------------------------------------
>>
>> 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?
>
>
> One of the issues the working group has had to deal with is that both
> cases of
> matching, with and without RDF D-entailment are reasonable.  There is
> no requirement that RDF datatype entailment is supported, nor is there a
> prohibition that it is not supported and the spec is intentionally not
> defining one way of the other.
>
> Another example is
>
> "10"^^xsd:integer and "X"^^roman:Numeral.  Same value - matched if the
> processor does D-entailment for roman:Numerals.
>
> RDF semantics says:
>
> [[
> These rules may not provide a complete set of inference principles for
> D-entailment, since there may be valid D-entailments for particular
> datatypes
> which depend on idiosyncratic properties of the particular datatypes ...
> ]]
>
>>
>> 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.)
>
>
> It does apply in the case of RDF term equality: we have a test case for
> this:
>
> http://www.w3.org/2001/sw/DataAccess/tests/data/ValueTesting/roman.rq
>
> (ARQ now can run with or without Roman Numeral support in FILTERs - by
> default
> it's turned off :-)
>
>>
>> [The float case is relatively simple, but more complex issues arise, for
>> example, with XML Literals]
>>
>
> You're right it coudl be clearer and it is worth picking out
> explicitly.  I've added at the end of 3.1
>
> [[
> Matching with RDF D-Entailment
>
> RDF defines D-Entailment. When matching RDF literals in graph patterns, the
> datatype lexical-to-value mapping may be reflected into the underlying RDF
> graph, leading to additional matches where it is known that two literals
> are
> the same value.
> ]]
>
>>
>> --
>>
>> 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/
>
>
>
> If this addresses the comments rasied, please respond with [CLOSED] in
> the subject to allow the issue tracking scripts to close this issue.
>
>     Andy
>
>
>

--

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 Thursday, 10 November 2005 04:35:52 GMT

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