RE: [AM] justify modeling (Why Model?)

(responding to Scott P)

> I phrased the statement badly.  Some of the modeling goals
> simply aren't met by code, so there would still be value in
> modeling even if code were cheaper than modeling.  However,
> in practice, code isn't cheaper than modeling, because the
> model is an abstraction of the code.

If one needs to write the code anyway, then the model is extra
cost.  Does it give extra value?  In reality, the rules of thumb
that decided when we should model, that were created 10
or 20 years ago, are now out of date because the relative
costs of modelling and coding have changed.  In truth, the code
*is* a model, and  much of the information one may produce
from a model could be produced from the working code.

Yes, there are still reasons to model, but there are now fewer
instances where these reasons apply.


>... you do those cheap, lightweight models, walk through them in
> various ways to validate them against your stories (use cases),
> revise or replace them, all in the course of a modeling session. 
> The iteration is 1-2 orders of magnitude faster.

Yet you still need to produce the code.  Once you have the code,
you can check that it does what you want.  Agreed, in some
circumstances one doesn't know what code to write, and in
*this* case a model can help.

Agreed that in larger projects, the degree of coordination needed
increases the cost of changing code, and thus more modelling
is justified because it saves more in rework than it costs.


Paul Oldfield

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
www.aptprocess.com

any opinions expressed herein are not necessarily those of
Mentors of Cally or the Appropriate Process Movement
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For more information about AM, visit the Agile Modeling Home Page at www.agilemodeling.com
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