A Plea for Schemas

David Megginson david at megginson.com
Tue Nov 2 18:41:36 GMT 1999

Paul Prescod <paul at prescod.net> writes:

> You can also use UML, set theory or Zen meditation to flush out
> misunderstanding but schema writing has the big advantage of
> providing immediate, interactive utility. Some customers say: "You
> mean we have to go to all of this work to understand our problem
> domain before we implement the code? Who has time for that?" The
> more saavy ones say: "finally we have an excuse to map our our
> problem domain without feeling like we are wasting time drawing
> pretty pictures."

Obviously, what works best will depend on the problem and on the
people and personalities involved.  In my experience, formal
specifications (schemas, UML diagrams, etc.) tend to be a serious
distraction early in a large project, because they allow people to
caught up in details far too soon.

Later on during a project's development, object models, data models,
DTDs, and their like can also give the false impression of actually
having accomplished something ("see, here's our object model on this
wall -- just follow it around out into the hall and down past the the
lunchroom") and thus postpone the realization that a project is in
serious danger of being delayed or of failing completely.  It's always
easier to keep spewing out more UML or DTDs than it is actually to
start building a working system.

Formal models do (as Paul says) help to flush out misunderstandings,
but they tend to find misunderstandings over fairly fine details,
which are appropriate to the later stages of a project.

All the best,


David Megginson                 david at megginson.com

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