The evaluation of software usability

The first type of definition was common in the 1970s but has proved largely useless for design purposes since it offers neither useful guidance for designers nor perspective for evaluators. The feature-based approach stems from the longstanding desire to specify in advance desirable interface attributes that enhance usability. However, this type of definition rests on an assumption that usability is an inherent part of the application. This assumption is false since one could always envisage a combination of users, with certain task demands, in a particular environment, for whom a given set of features would be sub-optimal. Recognizing this, most human factors professionals now employ an operational definition in their work.