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Subject: RE: Syntax Free Models


I hope I don't speak out of turn here, but it seems to me that sequence is
absolutely an aspect of syntax that we *must* avoid if we are to create an
information model that is capable of being expressed freely in various
syntaxes. Hierarchy, on the other hand, is something that exists within
specific contexts and can (hopefully) be modelled effectively across

I think there is a real danger of confounding hierarchy - which is highly
variable in many cases - and sequence. These are tightly tied in both XML
and EDI syntaxes today, but in markedly different ways. It is handy to be
able to express a hierarchy (or context) with a fixed sequence, but it would
severely limit the utility of the models we create if we are deterministic
about this up front.


Arofan Gregory

-----Original Message-----
From: Martin Bryan [mailto:mtbryan@sgml.u-net.com]
Sent: Monday, February 28, 2000 11:33 AM
To: Keith.Finkelde@btfinancialgroup.com; ebxml-core@lists.oasis-open.org
Subject: Re: Syntax Free Models


In response to your helpful comments I've tried to correct some of the
errors relating to Information Sequence naming that you kindly pointed out
in the earlier draft of my paper on a Syntax-Neutral Definition of Business
Semantics, and to clarify why I feel sequences are a vital component of the
model. Your views on these clarifications would be much welcomed, as would
anyone elses.

I have also taken this opportunity of extending the paper with a first draft
on the way I would like to see definitions of Information Messages,
Information Sets and Information Units exchanged. Whilst I intend, when I
get some free time, to extend this by adding ISO11179-based neutral
definitions, the initial XML models and examples should help you to see
where I am coming from.

I still need to work out models for recording the relationships between
Informatation Units (and maybe even Information Sets) and for recording the
relationships between Information Units and datatypes, but I would like to
start getting some initial reaction to what I am proposing before completing
these sections.

I still have doubts about the relevance of using state to record the
relationship between information units, as you propound. To me there is a
fundamental difference between what goes in the definitions and what goes in
the messages. In the definitions you need to tell people that the intention
is that the contents of one type of information unit should be derived from
another type of information unit. For a message instance you need to state
that this specific information unit was derived from that specific
information unit. What is needed then is some way of checking that the
derivation in the instance conforms to the derivation rules in the model. To
date I have not had time to work out a good way to do latter part of the
process. I am wondering if XSLT templates might provide a guide, but am
unsure yet how to declare this in a syntax neutral manner. An alternative
could be to use some of the techniques for requesting the monitoring of
events that were proposed for ISENS, etc, but at present I cannot see a way
to make this work over the long periods required for message definition
maintenance.  I have yet to find time to try to read up on the UML State
Machine work. Is there a simpleton's explanation of this available that
would be understandable to someone without a background in UML? Any
suggestions on how to approach these problems would be most welcome.

Martin Bryan
Technical Manager, The Diffuse Project
Project Manager, CEN/ISSS EC Workshop DAMSAD project group
The SGML Centre, 29 Oldbury Orchard, Churchdown, Glos GL3 2PU, UK
Phone/Fax: +44 1452 714029  E-mail: mtbryan@diffuse.org

For details of The SGML Centre visit http://www.sgml.u-net.com

For details of the EU-funded DIFFUSE project visit http://www.diffuse.org

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