Evaluation: 16 powerful reasons why not to do it--and 6 over-riding imperatives.

Evaluation is a concept which appears logical, and supplies the evidence which is sought by policy makers and those interested in obtaining and implementing an information system. However, it is difficult to obtain resources or other support to undertake evaluation studies, and indeed active opposition is often encountered. Unless this mistaken attitude is analysed and overcome, it will be impossible to optimise system applications, produce sound information policies, or practice evidence-based decision making in the information field. Experience is drawn from a range of applications in order to analyse the issues.