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RE: comment - RDFTM: Survey of Interoperability Proposals

From: Bernard Vatant <bernard.vatant@mondeca.com>
Date: Wed, 9 Mar 2005 03:07:35 +0100
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, <public-swbp-wg@w3.org>
Message-ID: <GOEIKOOAMJONEFCANOKCAEPLFKAA.bernard.vatant@mondeca.com>


Peter

Even if I am not responsible for a single line in the survey, please let me answer to some
of your remarks.

> First, however, a disclaimer:  I am a long-time skeptic of the entire Topic
> Maps paradigm.  I have tried several times to determine whether there is
> something interesting in Topic Maps and each time I have been unsuccessful.
> My skepticism colors many of these comments.

I remember some exchange we had a while ago and I see your viewpoint is steady on that ...
Could you be a little more explicit on what you mean here by "something interesting",
which you define in a very negative way by the fact that you did not find it. I've hard
time understanding negative definitions, sorry :)) What is it exactly you were looking
for, and that you did not find? Is it that you did no find anything useful at all (for
you), or anything usable, or anything that cannot be expressed otherwise, and better? Do
you think that what Topic Maps try to achieve has no interest, or is it the way they take
to do it? Or what? If I say : "I have tried several times to determine whether there is
something interesting in football and each time I have been unsuccessful" that only means
my incapacity to find interest in football,  but it does not change the fact that a few
people find it interesting, which I fail to understand, but which is a reality. So maybe
if I was looking at what people are finding in football rather than to football itself, I
would understand the interest of football :))

> The first problem that I see with the document is that it doesn't define
> the two paradigms.  There are no references to any of the defining RDF
> documents.  There are several references that could be considered to be
> defining Topic Maps - however, these do not show up until very late in the
> text and thus cannot be considered to be a definition for the purposes of
> this document.

Fully agreed

> This lack of a definition matters for reasons from both the RDF and the
> Topic Maps side.  RDF has undergone a significant change in the last few
> years from a pre-theoretic language with no firm foundation (see Resource
> Description Framework (RDF) Model and Syntax Specification
> http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/) to a full-fledged logic
> (see RDF Semantics http://www.w3.org/TR/rdf-mt/).  Which version of RDF is
> meant in the document?  Which version of RDF to the interoperability
> proposals refer to?  As well, what is the place of RDFS in the document?
> Is it included?  Is it excluded?

Good questions again.

> Topic Maps also are undergoing change, from the ISO definition (ISO/IEC
> 13250:2000 Topic Maps: Information Technology -- Document Description and
> Markup Languages, Michel Biezunski, Martin Bryan, Steven R. Newcomb, ed., 3
> Dec 1999.  http://www.y12.doe.gov/sgml/sc34/document/0129.pdf) to some
> recent draft proposals (Garshol, Lars Marius; Moore, Graham: ISO/IEC 13250:
> Topic Maps - Data Model (Final Committee Draft, 2005)
> http://www.isotopicmaps.org/sam/sam-model/ and Durusau, Patrick; Newcomb,
> Steven R.: ISO/IEC 13250: Topic Maps - Reference Model (Working Draft,
> 2004) http://www.isotopicmaps.org/tmmm/TMMM-4.6/TMMM-4.6.html).  Which
> version of Topic Maps is under consideration?  Does it matter?

Yes it matters a lot. Everyone having more or less followed the Topic Maps story over the
past years is aware of the neverending and passionate debate on what Topic Maps are, could
or should be, between tenants of the Topic Maps as data model (SAM) and tenants of a more
generic model(was TMMM, now TMRM). Actually the latter has considerably been changed since
the quoted reference, current version is
http://www.isotopicmaps.org/TMRM/TMRM-5.0/TMRM-5.0.pdf.

It's also true that none of the above makes for a formal semantic model. But please
consider that those who invented the paradigm, brought it to the status of an ISO
standard, and to the point of public consideration it is now, are a handful of dedicated
people who never had the support of neither major industries, nor academic research
credits. Several times I have asked some people as knowledgeable as you are, Peter, to
consider helping the TM community to try and deliver some formal model, or to come to
figure why there is no formal model possible, whatever. But I must admit that the answers
I had were not very helpful, more like "go and learn FOL, it's easy, all is right there in
my book, page x to y, come back when you have learnt and made your homework". Not very
helpful. In Mondeca we proposed at a point a mathematical model based on hypergraphs,
which we had used to built our software meta-model and architecture. It was neither well
received by TM folks (because it was maths, hence not readable) nor by RDF people (because
it was graph theory, hence "only syntax, not semantics" - that's what I was said).

> The second problem is that many of the interoperability proposals predate
> the finalization of the RDF Semantics.  Their current applicability is thus
> very suspect.  The document needs to carefully consider this aspect of each
> proposal.

I'm not sure of what you mean by "predate" here. Sorry.

> The third problem is that RDF and Topic Maps belong to different
> categories, at least so far as I can determine.

By essence, yes. But their story tends to show that differences in nature seem less and
less important compared to the community of what they both want to achieve. People do
things with TM that they could do with RDF, and vice-versa. Maybe they should not, maybe
it's hacking, in any case they do it. Why? Only out of poor understanding and mental
confusion, like football fanatics?

> RDF is now a formally-specified logic with a model-theoretic semantics.
> Topic Maps is not.  This difference matters, and needs to be taken into account in every
> discussion of the relationship between RDF and Topic Maps.

Agreed again.

> At best, there needs to be some way to determine that the interoperability proposals
> preserve logical equivalence on the RDF side.  At worst, there is no point
> in doing any mappings, as RDF and Topic Maps are simply incomparable.

Sorry but I think this latter position is not more sustainable that saying, say, English
and Chinese are simply incomparable. Sure there are many things in Chinese that are not
translatable in English, and maybe the other way round, but that does not mean there is no
point in trying to make Chinese-speaking and English-speaking folks trying to understand
each other.

> [For indications why this might be the case, consider that Topic Map merging as
> defined in http://www.isotopicmaps.org/sam/sam-model/ is claimed to not
> remove all redundant information in a topic map.  How then can it be
> determined whether a mapping is reasonable?  As well, the procedure defined
> therein does not terminate.]

It may be that here, TM folks have gone quite a long way on the issue of identification.
Merging is simply the final cleaning process triggered by identification, which is, as
Chris Welty pointed out in a recent message, a very important and difficult issue, and I
remember Pat Hayes also writing quite a while ago that identification issue was "sadly
overlooked" by various SW specifications. What TMDM acknowledges, if I catch it well, is
that even when process of merging is achieved, following the identification rules, one can
never be sure if some elements which have not been merged could yet still actually
represent the same subject, but had not been merged because there was no identification
rule allowing to merge them. That's what "remaining redundant information" means. In what
is OWL-RDF different in this respect? The famous example of the robber and the speeder is
a too well ending story ... most of the time, the robber and the speeder *are* actually
the same guy, but there is neither facts nor rules sufficient to prove it, and, as in the
real life, "the procedure does not terminate", and the robber keeps speeding (and the
other way round), and the police does not know.

Best regards

**********************************************************************************

Bernard Vatant
Senior Consultant
Knowledge Engineering
bernard.vatant@mondeca.com

"Making Sense of Content" :  http://www.mondeca.com
"Everything is a Subject" :  http://universimmedia.blogspot.com

**********************************************************************************
Received on Wednesday, 9 March 2005 02:07:48 GMT

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