http://distributedteams.org/2007/06/08/defined-vs-empirical-process-control/
http://en.wikipedia.org/wiki/Empirical_process_%28process_control_model%29
The empirical model of process control provides and exercises control through frequent inspection and adaptation for processes that are imperfectly defined and generate unpredictable and unrepeatable outputs. See statistical process control.
For many years software development methodologies have been based on the defined process control model. But software development isn’t a process that generates the same output every time given a certain input.
The agile software development method Scrum is based on the empirical process control model.
