Re: [AM] The Spiral Model

----- Original Message ----- 
From: "Scott Ambler" <[email protected]>
To: <[email protected]>
Sent: Saturday, February 14, 2004 8:27 AM
Subject: RE: [AM] The Spiral Model


>
> I agree with Charlie.

Re: previous post.  Also, I don't see a particular connection between the
Agile Manifesto and Spiral.

> On a tangential note, here's an observation that I made about Spiral a few
> years ago in my Process Patterns book:
>
> The main advantage of the Spiral Development process pattern is that it is
> a more realistic look at software development, as it recognizes the fact
> that you often must revisit each project phase throughout the development
> process.  It also directly includes prototyping as a project phase,
> providing the opportunity to include users to a greater extent in the
> development process.  The disadvantages of the Spiral SDLC include the
fact
> that it is complex and that it still is not completely accurate: sometimes
> we realize during one phase that we need to immediately go back and redo a
> previous one, perhaps go from prototyping directly back to risk analysis,
> without continuing on to the next phase.

Good point.  The Spiral methodology, as it has been described recently and
is being taught, has no explicit activity dedicated to handle such a case as
you describe.  However, it could be argued that the description of the last
defined activity in a spiral implicitly, the planning activity, includes the
possibility to replan the current spiral if the decision is not made to
continue to the next spiral.

If one were to devise criterion based "exit" and "re-entry" points available
for each spiral, if you must have rigidity, or otherwise, a single override
activity to exit re-enter anywhere as appropriate, then perhaps it wouldn't
be such a disadvantage.

> The paragraph above accompanied a diagram of the spiral lifecycle.  In the
> diagram you "spiral through" requirements, requirements validation,
> analysis, ....  basically mini-waterfalls.  That's what I was saying
wasn't
> accurate, IMHO.

I remember a rather silly discussion here about mini-waterfalls.  To avoid a
similar discussion resulting from a comment here, is that there are certain
activities unavoidable in good software development.

1. Conceptualize what will be done such as the design or the test in TDD, or
scribbles on paper before something is coded - or at least the thought
paths - or thought then code cycles that occur during the conceptualization
of what is coded.
2. Something is coded.
3. The code is verified, either by planning or by operational use (e.g.
customer says it doesn't do what he said it should do.)

One therefore could argue that this is design, code, test, or a
mini-waterfall.

Not sure what you mean by your last sentence.

> - Scott
>
>
>
>
>
> At 10:05 PM 2/13/2004 -0800, Charlie wrote:
> >Having read the question and ensuing answers I'm struck that nobody has
> >mentioned this:
> >
> >Agile methods deal with people and how they work together. Historically,
> >this has been
> >"out of scope" for software development methodologies. If we compare
> >approaches while
> >abstracting away this important difference, they may appear similar, just
as
> >an auto
> >is like a wagon if you abstract away the source of motive power.
> >
> >When we choose to abstract away people in our discussion, we are being
> >non-agile ourselves.
> >
> >Charlie Poole
> >[email protected]
> >www.pooleconsulting.com
> >www.charliepoole.org
> >
>
> For more information about AM, visit the Agile Modeling Home Page at
www.agilemodeling.com
>
>
>

For more information about AM, visit the Agile Modeling Home Page at www.agilemodeling.com
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