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Re: [proposed close: pfps-05]

From: pat hayes <phayes@ihmc.us>
Date: Thu, 14 Aug 2003 01:00:00 -0700
Message-Id: <p06001a08bb5effff2f65@[10.0.1.2]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-rdf-comments@w3.org


>The last-call version of RDF Semantics contains many significant errors.  I
>have pointed out many of these.  I even pointed out some of them in the
>last-call version before RDF Core went to last call.  Nevertheless, the RDF
>Core WG decided to go to last call with these comments unaddressed.
>
>One of these signficant errors was that the RDFS closure rules were
>incomplete.  I have pointed out problems with the closure rules in various
>versions RDF Semantics, starting on 26 September 2001
>(http://lists.w3.org/Archives/Public/www-rdf-logic/2001Sep/0031.html).  I
>reported problems with the closure rules in the last-call candidate on 27
>December 2002
>(http://lists.w3.org/Archives/Public/www-rdf-comments/2002OctDec/0297.html).
>
>On 24 January 2003, I made a formal last-call comment concerning the
>completeness of the RDFS closure rules
>(http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0090.html),
>which states
>
>>The closure rules for RDFS are incomplete.  For example,
>>     ex:foo ex:prop "a" .
>>RDFS-entails
>>     ex:foo ex:prop _:x .
>>     _:x rdf:type rdfs:Resource .
>>However, this does not come out of the RDFS closure rules.
>>This means that the RDFS entailment lemma is false.
>
>Since then many changes have been made to the RDF model theory that have
>affected this issue.  In each version of RDF Semantics up until at least
>the 15 July 2003 version the RDFS closure (or entailment) rules have been
>incomplete and the RDFS entailment lemma has been false.  I have
>repeatedly pointed out these problems.

All of this is correct. There have been many 
errors of detail, many of which you have caught, 
and for which detailed checking I am grateful. 
However, the W3C process requires us to identify, 
respond to and gain reactions to particular 
comments, one at a time. The prehistory of these 
comments has to be put aside in order that the 
process may be formally closed; in any case, the 
prehistory seems to me to be irrelevant to the 
current issue. There were many reasons (some of 
them personal, some of them concerned with global 
timeschedules) why we went to LC with errors in 
the document. If you feel personally offended by 
this, I am sorry that you should have felt that 
this action was in any way a personal affront: it 
was not meant or intended to be so.

>In the 31 July 2003 version of RDF Semantics, the RDFS entailment rules are
>still incomplete.

I do not believe this to be true, and you have 
not provided any evidence for it. Your message 
referring to the 31 July 2003 version complained 
that you "had hoped that the entailment rules 
would finally end up as complete syntactic 
characterizations of entailment." You gave no 
indication what had given rise to this hope, and 
it was not one that you had ever expressed 
before.   No version of the semantics document 
has ever claimed to offer a set of rules which is 
complete in this strong sense ; strong 
completeness was never the goal of the rule 
systems.  This was perfectly clear in the LC 
version of the documents.

If this is what you now mean by 'incomplete', 
then the sense of this word has changed between 
your previous comments, cited earlier, and your 
recent response.

I believe that the rules are complete in the 
sense stated in the document, a sense which has 
been stable since the very first version of the 
document.

>  I view this as distasteful, even just by itself.

Under the circumstances, I do not feel obliged to 
respond to this. I do not agree with it, 
naturally enough. If this is a comment, then I 
will advise the WG not to accept it. In the 
meantime, however, we still need a response from 
you on substance of the previous comment, to wit, 
the completeness of the entailment rules, in the 
sense stated in the text.

>It is
>not obvious to me that the RDFS entailment is false.  (See below for a vital
>caveat on this.) However, I have not yet had a chance to investigate the
>situation in as much depth as I would like so I am not prepared to indicate
>that I view the RDFS entailment lemma as true.

There is a proof sketch in the document which you 
might find useful; and the document has been 
reorganized so as to make the correspondences 
between the semantic conditions and the 
entailment rules more apparent.

>I believe that my messages concerning this issue have not gone beyond the
>incompleteness of the RDF closure (now entailment) rules.

Until recently that was true, and the response to 
which I was referring in my message also referred 
to completeness of the rules in the sense that we 
have been discussing until recently.  But as I 
indicated, the meaning of 'complete' seems to 
have changed, which is why we are having this 
debate.  Your 'dissatisfaction' expressed on the 
3 August seems to refer to a new topic.

>  I further
>believe that the known problems going into last call and the significant
>post-last-call changes require that the RDF Core working group adequately
>address new comments on their documents and not limit simply address a
>narrow reading of the comments received during that last-call review
>period.

I do not accept this. The WG has tried to adhere 
to W3C process rules as far as possible. We 
allowed comments for a considerable period after 
the LC, and followed up with you and other 
commentors to clarify the issues that were 
raised. We have responded as promptly as possible 
to subsequent comments and observations of a 
technical nature; but at some stage this process 
has to stop. I do not accept that your having 
made a detailed technical observation on the LC 
documents gives you an open-ended licence to 
create new objections or raise new 
dissatisfactions.

>I categorically reject the view that changes to one of the RDF documents
>must be considered in isolation to determine whether a comment has been
>adequately or satisfactorily addressed

The W3C process requires us to identify comments, 
respond to them and to seek acceptance of the 
responses, one at a time.

>and that other aspects of the RDF
>specification must be excluded from this determination.

Of course other aspects need not be excluded from 
consideration; however, the W3C process requires 
us to assign discussion to threads rooted in the 
archived comments.

>The RDFS (and RDF) semantic conditions also depend on the treatment of XML
>literals in RDF.

That is true, but that issue has been considered 
on another thread rooted in a LC comment by you, 
archived as pfps-06. I have deliberately 
refrained from asking you to respond on that 
thread until the issue has been settled.

>This treatment has recently been changed in a significant
>manner that affects both the completeness of the RDFS entailment rules and
>the correctness of the RDFS entailment lemma.  The definition of XML
>literals in RDF is in RDF Concepts, and is significantly flawed in the
>current editor's draft (of 28 July 2003).  Some of these flaws have
>reasonably obvious fixes, but others do not, and indeed appear to be the
>subject of vigorous debate.  The changes needed to fix the treatment of XML
>literals in RDF may affect the completeness of the RDFS entailment rules
>and the correctness of the RDFS entailment lemma.

I have made it clear to the WG that the semantics 
requires that XML literals denote literal values 
which are 1:1 with the lexical forms of the 
literals but distinct from them (and from 
xsd:strings). These conditions are stated 
explicitly in the semantics document. Please 
assume that these conditions will be satisfied 
and review the semantics document on that basis. 
I believe that these conditions are sufficient to 
establish the correctness of the lemmas in the 
document.

>My reading of the treatment of RDF XML literals in RDF Concepts is that
>several lexical strings can map into the same value.

That is not my understanding nor Jeremy's. If you 
are right, the wording will be changed to avoid 
the possibility of this interpretation.  It would 
be helpful if you could respond the Semantics 
document on this basis and to the Concepts 
document on the assumption that its definitions 
are intended to provide this structure.

>  Under this reading,
>the RDFS entailment lemma is false because it does not recognize different
>XML literals that denote the same value.  In any case, the situation with
>respect to the completeness of the RDFS entailment rules and the
>correctness of the RDFS entailment lemma cannot be determined until the
>treatment of RDF XML literals is fixed and finalized.
>
>
>So, I do not consider that my comment has been adequately addressed.

If the comment pfps-05 is concerned with XML 
literals, can we identify pfps-05 and pfps-06 as 
being essentially the same comment?

Pat

-------------

>Peter F. Patel-Schneider
>Bell Labs Research
>Lucent Technologies
>
>
>
>
>From: pat hayes <phayes@ihmc.us>
>Subject: [proposed close: pfps-05]
>Date: Sat, 9 Aug 2003 21:38:45 -0700
>
>>  Peter;
>>
>>  In your comment
>>
>>  http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0090.html
>>
>>  archived as pfps-05 and accepted by the WG:
>>
>>  http://www.w3.org/2001/sw/RDFCore/20030123-issues/#pfps-05
>>
>>  you indicated that the closure rules for RDFS in the LC version of
>>  the semantics document were incomplete, giving an example inference.
>>  The WG accepted this comment and made various changes to the RDFS
>>  (and other) rules, and indeed to the RDFS semantics, in order to
>>  establish completeness of a relatively simple rule set for RDFS.  You
>>  noted that a graph could be RDFS-inconsistent by virtue of the XML
>>  datatyping implicit in RDF, and we made further modifications to
>>  handle this case.
>>
>>  Your next response, however
>>
>>  http://lists.w3.org/Archives/Public/www-rdf-comments/2003JulSep/0178.html
>>
>>  seems to have enlarged the topic further, to be a kind of general
>>  complaint about the style of the document and the way that the rule
>>  sets are stated. I have replied to you on this general issue; it may
>>  be that we simply disagree about stylistic matters; but in any case,
>>  I do not feel that the discussion at this stage is concerned with the
>>  topic of the original comment which was accepted by the WG. I note
>>  that in your most recent message cited above you use 'incomplete'
>>  apparently in a non-technical sense; and that the property of the
>>  lemmas which incurs your "deep dissatisfaction"  - that they operate
>  > by reducing vocabulary entailment to simple entailment - has been
>>  present since the very first draft of the semantics document, and is
>>  stated explicitly in the test, but has never been remarked on
>>  previously: in particular, none of the comments on the LC version of
>>  the semantics document referred to this negatively. I also note that
>>  this style of rules has been used directly by implementors apparently
>>  with reasonable success with graphs of up to O(10|6) nodes.
>>
>  > As the formal process is now very late, I must ask you to please
>>  indicate whether the changes to the document mentioned in earlier
>>  emails are an acceptable response *to the point you raised in your
>>  original comment*, viz. the incompleteness, in the sense stated in
>>  the document, of the RDFS closure rules (now called entailment
>>  rules). This would not, of course, require you to register your
>>  satisfaction with every aspect of the document, but it will enable us
>>  to proceed with the W3C processes as far as this particular issue is
>>  concerned.
>>
>>  Please Cc your reply to rdf-comments.
>>
>>  Thanks.
>>
>>  Pat
>>
>>  --
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Received on Thursday, 14 August 2003 04:00:07 GMT

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