Development of indicators for integrated system validation

Integrated evaluation of complex artefacts such as NPP control rooms are claimed to require improved validation approaches. A notion of system usability is introduced. It denotes connecting decisions concerning the appropriateness of artefacts to criteria that indicate the system's ability to fulfil the objectives of the activity system and to promote their appreciation in users' situated actions. System usability is evaluated via an operation-oriented evaluation concept. It includes evaluation of user performance and experienced appropriateness of the system. New types of performance evaluation criteria are introduced. The new indicators and criteria may be derived with the aid of a Core-Task Analysis modeling process