TOWARDS ESTABLISHING A SCORE OF USABILITY EVALUATION

The paper deals with the problem of finding a methodology which allows obtaining a score of usability evaluation for various kinds of user interfaces. The evaluation is in principle based on a definition of a set of properly chosen key characteristics affecting the usability of the user interface. Since the crisp numbers cannot directly express vague terms or ambiguities, theory of fuzzy logic has been chosen as the most appropriate apparatus to deal with the uncertainty. The evaluations expressed in users natural language are converted to the set of normalized evaluation words. A fuzzy inference system that uses expert knowledge is used to match the best possible approximation of evaluation with the knowledge included in the fuzzy rule base. The output of inference system is obtained by using common defuzzification methods. Proposed methodology was successfully implemented into software application Fuzzy Usability Evaluator that has been used for evaluating usability of Web portals in Public administration.