There are three purposes for evaluation: evaluation for action to aid the decision making process, evaluation for understanding to further enhance enlightenment and evaluation for control to ensure compliance to standards. This article argues that the primary function of evaluation in the "Catherine Wheel" computer-based assessment (CBA) cyclic model is evaluation for action and secondary functions are evaluation for understanding and control. By studying segment and cyclic dependencies, conducting a risk analysis and identifying key stakeholders it is possible to identify where action evaluation has the most effect, what is required to be evaluated, who will perform the action and how it will be controlled. Each segment and cycle in the CBA model must therefore be monitored and the observations made must have meaning for the elimination or reduction of pedagogic, operational, technical non web-based, web-based and financial risks. It is important to consider stakeholders because they have differing views on what is most important in the evaluation process and inevitably will be involved in the evaluation process itself. CBA system stakeholders include management, academic, support and administrative staff together with external verifiers and students. The information gained from these stakeholders provides quality enhancement and assurance and forms the basis for change. (Contains 2 figures and 3 tables.)