• organizational cybernetics;
  • viable system model (VSM);
  • law of requisite variety (LRV);
  • business process management;
  • computer simulation

This paper approaches business process diagnosis from a cybernetic viewpoint. Ashby's law of requisite variety is used to understand deficiencies of business processes. A case of a purchasing process that suffers from low effectiveness and long waiting times of purchase requests is considered to be improved using cybernetic concepts and models. It is discussed that the problems with the process result from a lack of requisite variety. Then, Stafford Beer's viable system model (VSM) is used to ease the problems by balancing the varieties. The static and dynamic aspects of the process are modelled using data flow diagram (DFD) and integrated computer simulation model. It is demonstrated that after applying the VSM, the duration of the process will decrease largely. This is the first study that uses cybernetic law and VSM for improvement of a purchasing process through computer simulation and DFD. Copyright © 2011 John Wiley & Sons, Ltd.