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

| From: Paul Oldfield<[email protected]>
| 
| (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| or 20 years ago, are now out of date because the relative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.
---

The point is to try to write the code once and do limited refactoring
afterward, as opposed to writing it once, throwing it away, writing it
again, throwing it away, etc., while you try to decide whether you're
going at it the right way.  Models are cheaper than code, so it's MORE
AGILE to do the early iterations in that form.

---
| 
| >... 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.
---

The models are part of deciding what you want to do, both in terms of
what the solution looks like on the outside (to the user) and what it
looks like on the inside (what the pieces are and how they play
together).

scott

-- 
scott preece
motorola urbana design center (il67), 1800 s. oak st., champaign, il  61820  
e-mail:	[email protected]	fax:	217-384-8550
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