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RE: issues to be resolved before last call

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Fri, 17 Jan 2003 14:53:20 +0100
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, <www-webont-wg@w3.org>
Message-ID: <BHEGLCKMOHGLGNOKPGHDIEPDCAAA.jjc@hpl.hp.com>


> Here are some issues that I feel must be resolved before OWL goes to last
> call.

How many really must be resolved now, and cannot be addressed as part of the
last call process on RDF.
None of them seem to be in order for webont to discuss, other than as
comments about RDF that need fixing.

In fact, this seems to be largely a stylistic problem between Brian (series
editor) and yourself. Brian decided that he wanted to operate a document
freeze process before last call - you clearly believe that your problems are
sufficiently important to merit changing the frozen documents. I,
personally, while not much liking the document freeze policy, do not think
that your issues cross that bar - except for the social meaning one, for
which RDF Core explicitly decided to take it as a last call issue.

> I have battled to get the RDF issues resoved, but to little
> success.  I would like to have formal votes on all the proposed
> resolutions
> herein.
>
>
>
> Issues with XML Schema:
>
> 1/ The value spaces of xsd:decimal and xsd:float are not disjoint.  Right
>    now in both XSD datatyped RDF and OWL the denotation "234.5"^^xsd:float
>    is an element of the class extension of the denotation of xsd:decimal.
>
>    PROPOSED RESOLUTION:  The class extensions of xsd:decimal and xsd:float
>    are not disjoint.   The class extension of xsd:float is a subset of the
>    class extension of xsd:double.

Not acceptable.
RDF Core decided that this needed to be resolved with the XML Schema WG, and
that work will start soon (after Last Call has been entered).

>
>
> Issues with RDF Concepts:
>
> 1/ The notion of social meaning has no place in the specification of a
>    formal system.
>
>    PROPOSED RESOLUTION:  Social meaning, as defined in the RDF Concepts
>    document, has no effect whatsoever on the meaning of OWL ontologies.
>
>    NB:  I view this as an extremely serious issue.
>
>

RDF Core decided that this issue should be taken at last call. Your position
seems diametrically opposed to that of TimBL, and really we need to get the
two of you in a room and leave you to fight it out - will you be at the
plenary?

> Issues with the RDF model theory:
>
> Caveat: The RDF Semantics document may change, and has recently changed.
> The issues here may be affected by any upcoming change, and have been
> affected by the recent changes, which I have not completely analyzed.  I
> have not yet received responses to many of my recent comments on the RDF
> model theory nor have I been given any sort of change list for any of the
> recent changes to RDF Semantics.  The following is only my best guess at
> the current situation.
>
> 1/ The class extension of rdfs:Literal does not necessarily include
>    strings.  Right now, "a" rdf:type rdfs:Literal . is not
> RDFS-entailed by
>    the empty graph.  Also, without the following fix, "a" rdfs:type _:x
>    . _:x owl:complementOf rdfs:Literal . is not OWL Full entailed by the
>    empty graph.
>
>    PROPOSED RESOLUTION:  Add to the second table in the OWL model theory
>
> 	if E is 	then CEXTI(SI(E)) =
> 	rdfs:Literal	LV
>
>    As well, add a note to the effect that this is a change to the meaning
>    of rdfs:Literal.
>
>    NB:  This condition *is* already present.  However, I feel that the
>         WebOnt working group should explicitly resolve this point.
>
>    NB:  This is a significant extension of the RDFS model theory,
> with lots
>         of observable consequences.

This is a bug with RDF Semantics, work with Pat and get it fixed; either
before or after last call (IMO).

>
> 2/ XSD-interpretations in RDF include the problematic XML Schema
>    datatypes.
>
>    Current situation: OWL interpretations are defined from
>    D-interpretations where D consists of the appropriate XML Schema
>    datatypes, not from XSD-interpretations.
>
>    PROPOSED RESOLUTION:  OWL interpretations are not defined from
>    XSD-interpretations.
>
This looks like another comment about RDF docs that is best raised as a last
call comment. It really does not seem critical to me that we fix this before
OWL goes to last call.

> 3/ There is no definition of literal strings or language tags in the RDF
>    Schema document.
>
>    PROPOSED RESOLUTION:  Literal strings are Unicode strings.
>
>    PROPOSED RESOLUTION:  Language tags are as in RDF Concepts.
>

These are minor bugs with the RDF Vocabulary document. Report it and it will
be fixed.

> 4/ There is contradictory and unclear information with respect to
> what is a
>    datatype as well as to the treatment of typed literals.  Datatypes are
>    sometimes elements of the semantic domain, denoted by URI references,
>    and sometimes the URI references themselves.  There is no necessary
>    connection between the intended URI reference for a datatype and the
>    datatype itself.
>
>    PROPOSED RESOLUTION:  A datatype is a formal object, consisting of
>    a URI reference, a lexical space (which is a subset of the Unicode
>    strings), a value space, and a lexical-to-value mapping from
> the lexical
>    space into (not onto) the value space.  In a
>    D-interpretation containing the datatype d = <U,L,V,L2V>,
>    a/ D <= ICEXT(I(rdfs:Datatype))
>    a/ IS(U) = d;
>    b/ ICEXT(d) = V;
>    c/ for l in L and t a langauge tag, IL("l"^^U) = L2V(l) and
> 		IL("l"@t^^U) = L2V(l)
>    d/ for l not in L and t a language tag, IL("l"^^U) is not in LV and
>  		IL("l"@t^^U) is not in LV
>
>    NB:  Under this resolution rdf:XMLLiteral is *not* a datatype.
>
>    NB:  Under this resolution I("aa"@en^^xsd:decimal) is not necessarily
> 	the same as I("aa"@fr^^xsd:decimal).
>

This is an editorial deficiency of the RDF documents.

> 5/ The non-normative parts of the RDF model theory, including the closure
>    rules and the translation to Lbase, have many errors.
>
>    PROPOSED RESOLUTION: The W3C Web Ontology Working Group notes that the
>    RDF Semantics document has numerous errors in its non-normative
>    sections.  None of these sections are to be used to provide guidance as
>    to the meaning of RDF or OWL where the normative sections of the RDF
>    Semantics document are unclear, contradictory, or silent.
>
>    NB: I feel very strongly that WebOnt needs this resolution.  There are
>        important places, such as the definition of what is a datatype and
>        the treatment of rdf:XMLLiteral, that are unclear or contradictory
>        in the RDF Semantics document, but where the non-normative sections
>        of the document clearly use only one of the possible
>        interpretations.
>

Jeremy
Received on Friday, 17 January 2003 08:53:34 GMT

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