From http://www.controlchaos.com/debate.htm ( Broken Link )

Models of empirical processes are derived categorizing observed inputs and outputs, and defining controls that cause them to occur within prescribed bounds. Empirical process modeling involves constructing a process model strictly from experimentally obtained input/output data, with no recourse to any laws concerning the fundamental nature and properties of the system
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The ScrumProcess, and other AgileProcesses, use an empirical process control model instead of a DefinedProcess control model.  This means that they depend on InspectAndAdapt cycles, instead of phases, hand-offs, sign-offs and blame.