Agile Attitudes- The Essence of Agile - Empirical Process vs. Defined Process

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Agile Attitudes
Volume 2, Issue 08                                    July 25, 2005
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The Essence of Agile - Empirical Process vs. Defined Process

                by Nancy Van Schooenderwoert

In software development there are two choices: either you plan your
project thoroughly or you just "wing it". Right? I used to think so, but
not any more. There is a third alternative.


In the world of industrial process control there are two major
approaches to controlling any process " the "defined" process control
model and the "empirical" model. The defined model is what you are using
when you attempt to thoroughly plan a software project. "Winging it" is
just another word for chaos. So that leaves the empirical process
control model " what is that?


Empirical process control is the essence of all agile methodologies. It
expects the unexpected. In defined process control, every piece of work
must be completely understood. Given a well-defined set of inputs, the
same outputs are generated every time. Given clear, stable requirements
and well-understood technologies, a software project can be predicted.
But when do we ever see those preconditions?


Empirical process control is used in situations where the inputs are
varying, and the process is too complex to produce repeatable outputs.
Frequent inspection and adaptation is used to control such processes.


In his book "Agile Software Development with Scrum", Ken Schwaber
describes how he tried using defined software process methods in his
software company with very unsatisfactory results. He met a group of
leading process theory experts at DuPont, and described his problem to
them. As Ken tells it: "They inspected the systems development processes
I had brought them. I have rarely provided a group with so much
laughter. They were amazed and appalled that my industry, systems
development, was trying to do its work using a completely inappropriate
process control model. They said systems development had so much
complexity and unpredictability that it had to be managed by a process
control model they called 'empirical'. They said this was nothing new,
and all complex processes that weren't completely understood required
the empirical model."


This was a turning point for Ken. He realized what was so wrong in the
software industry " "we were wasting our time trying to control our work
by thinking we had an assembly line when the only proper control was
frequent and first-hand inspection, followed by immediate adjustments."


On first hearing about agile software practices, many people wrongly
assume that it's just a form of "winging it" since it certainly is
different from the defined process control method. Nothing could be
further from the truth. Empirical control is a completely legitimate,
disciplined way to control a complex process like software development.
When you use a defined approach to control software development, you go
too far on assumptions in an attempt to plan sufficiently. You get a
false sense of security. Now you know what we meant last time when we 
said that your "plan" will build nothing but a house of cards.


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