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RE: comment - RDFTM: Survey of Interoperability Proposals

From: Steve Pepper <pepper@ontopia.net>
Date: Wed, 23 Mar 2005 19:04:05 +0100
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: "SWBPD list" <public-swbp-wg@w3.org>

* Peter Patel-Scheider

| This is collection of comments on RDFTM: Survey of Interoperability
| Proposals http://www.w3.org/2001/sw/BestPractices/RDFTM/survey-2005-02-24.
| 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.

Thank you for stating this up front.

| 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.

All relevant defining documents (i.e., RDF Concepts, RDF Schema, OWL,
and RDF Primer) are now referenced in Section 1, Introduction.

| 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?  

It is now clearly stated

1) that most of the proposals in the Survey were written before the 2004
   finalization of the above-mentioned documents; and

2) the extent to which RDF Schema and OWL are considered relevant to the
   Survey and the further work of the RDFTM task force. 

| 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 and no. Given that the proposals being discussed were written over
a three-year period, during which the ISO standard was being elaborated,
they are indeed based on different "defining documents". This is made
clear in the survey, as is the fact that a new set of definitive documents
are nearing finalization in ISO.

| 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.

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

RDF and Topic Maps may well belong to different categories (that would be
in the eye of the categorizer). Nevertheless, the SWBPD has determined
that there is both a need and a potential for achieving some level of
interoperability at the data level. That does not mean that either RDF or
Topic Maps will ever be able to replace the other: In that sense they may
be "incomparable" It does however mean that there can be some benefit to
be derived from being able to move data between the two. My personal
experience tells me that the market certainly thinks so.

| The fourth problem is that I do not see any utility for the document as a
| W3C Working Note.  What does the note have to do with any real output of
| the task force?  Perhaps the task force needs this document for its
| internal deliberations, but in my opinion this doesn't require a
| full-fledged note.  (Consider the situation in the WebOnt working group
| where there were many internal documents used to produce OWL.  These
| documents are recorded in the records of the working group kept by W3C, but
| did not become W3C Working Notes.)

The charter of the RDFTM task force states clearly that the deliverables
will be (1) a survey, and (2) interoperability guidelines. (1) was deemed
to be necessary to provide a foundation for (2), hence the intention to
publish it as a WG Note (nota bene, an SWBPD Working Group Note, not a
W3C Note).

Best regards,


Steve Pepper <pepper@ontopia.net>
Chief Strategy Officer, Ontopia
Convenor, ISO/IEC JTC 1/SC 34/WG 3
Editor, XTM (XML Topic Maps 1.0)
Received on Wednesday, 23 March 2005 18:04:45 UTC

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