[xtm-wg] Status of the Conceptual Model

[Daniel Rivers-Moore <daniel.rivers-moore@rivcom.com>]

There have been several statements recently on this list about the current
state of the XTM Conceptual Model. We have heard that it is "not finished";
we have heard that there are several "layers" still to be done. Let me
clarify.

The layers of the model, as specified in the brief to the Conceptual
Modelling Subgroup when it was formed by the XTM Authroring Group, are as
follows:
1) A UML model formalising the conceptual model underlying XTM.
2) A UML model formalising the constructs of the XTM interchange syntax.
3) A UML model formalising the mappings between 1 and 2 above.

Item 1 was finished on day 2 of the Dallas meeting, and presented to the
plenary session on the morning of day 3.

Items 2 and 3 can only be done when the interchange syntax is known. On the
morning of day 3 of the Dallas meeting, the Interchange Syntax Subgroup
indicated that it had not finished its work, and requested a further
session. To this it was countered that there would then be insufficient time
to ensure harmonisation between the syntax and the conceptual model. Both
groups were therefore dissolved by the Authoring Group, and it was decided
that the remaining work would be done by the Authoring Group as a whole. The
Group then did some work on harmonising vocablary, and delagated various
subgroups to undertake various writing and editorial tasks in order to
produce a spec for publication.

The current status of the Conceptual Model itself (item 1 above) is as
follows:
- It is complete, in the form presented by the Conceptual Modelling
Subgroup, and deemed by the members of that subgroup to be sufficient and
appropriate for XTM 1.0
- It is subject to review, and may be modified if deemed appropriate by the
Authoring Group as a whole
- There are some requests on the table for further enhancements to the
templating construct. It was the view of the Conceptual Modelling Subgroup
that such enhancements are not needed for XTM 1.0 but would be very useful
in subsequent versions of XTM. (For what it is worth, that is still my
personal view.)

The status of the UML model of the syntactic constructs of the XTM
interchange syntax (item 2 above) is as follows:
- The syntactic constructs are currently expressed in DTD syntax
- They are currently under review
- Some members of the group have expressed the view that, notwithstanding
that review process, they should not be changed; others have expressed the
opposite view
- Once there is agreement on what the interchange syntax is (expressed in
the form of a DTD), it will be a quite simple matter to create a UML
representation of those constructs, but this task has not yet been begun.

The status of the mapping between 1 and 2 (item 3 above) is as follows:
- I have prepared a first draft of a prose description of that mapping,
based on the current state of the syntax, and have postged it to this list
- In that document, I have raised specific issues where I find that that
mapping does not work
- In order to make the mapping work, either the conceptual model, or the
syntax, or both, will therefore need to be changed, or I will have to be
shown that I am mistaken and that an adequate mapping can be found without
changing either.
- The UML representation of the mapping has not yet been done. This will not
be a large task, once the mapping itself is clarified and the issues
resolved, though it will be a slightly larger task than making the UML
representation of the syntactic constructs themselves.
- The UML representation of the mapping cannot be done until we have done
the UML representation of the syntax, because it will consist of defined
relationships between the components of the syntax and the components of the
conceptual model.

A request has been made for a copy of the complete conceptual model in its
current form to be made available. I shall do that in a separate posting.

Daniel
(chair of the former Conceptual Modelling Subgroup of the XTM Authoring
Group)


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