[sc34wg3] a TM Application Definition example

[Steven R. Newcomb]

Robert Barta <rho@bigpond.net.au> writes:

> Do you think it would be possible to have a more
> concise notation for a TMA definition?

I hope so.  Do you have any ideas?

> Even with this tiny example the rules and constraints
> are exceedingly repetitive and make this look much
> more complicated than it might be.

Aside from that, though, does the TMA do what
needs to be done?

Sometimes we have to adapt to the complexity of the
problems we face.  I suspect that the first time people
outside the SGML movement saw DTDs, they, too, wondered
why the solution to the problem of application-neutral
information interchange should be so complicated.

> This also may apply to TMM itself.

When we drafted the current version of the TMM, we
decided to document reciprocal pointers from the
perspective of both ends, instead of from only one of
them.  This made the document larger and apparently
more complex than it would have been if we had
continued to use the idea of "bi-directional arcs", as
we had in the two previous drafts (the substance of
which, by the way, was the same at that of the current
draft).  It could be argued that the new approach is
unnecessarily repetitious, but it offers the advantage
that implementers can clearly see, as they implement
each part of the assertion model, everything relevant
to the part that they're implementing.  The new
approach is also clearer in that the consistency rules
by which the conformance of implementations will be
judged are all stated (and re-stated, as necessary)
wherever they have effect.  We thought that, this way,
implementers would be much less likely to misunderstand
the text.

Simplicity is an extremely slippery thing.  What is
simple from one perspective looks complex from another,
and vice versa.  In international standards, I
personally think it's better to err on the side of
clarity, than on the side of brevity (or on the side of
any other form of *apparent* simplicity).  I think
Einstein's famous remark applies here: "As simple as
possible, and no simpler."  That was the mark we were
trying to hit in N0393.

> And: Is the structure of such a TMA document
> predefined?

I think it makes sense to develop a DTD in the ISO
context for this purpose.  We could even call it
"TMCL", if we wanted to.  It should be a Topic Map
interchange syntax -- one that is designed for the
special purpose of specifying self-describing TMAs.
(Just as XTM is primarily designed for the special
purpose of specifying finding tools, such as indexes,
etc.)

-- Steve

Steven R. Newcomb, Consultant
srn@coolheads.com

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