QoS Criteria for Real-time Systems

Abstract

There are many questions one may ask oneself when discussing the quality of a real-time system. Generally, there are two typical kinds of questions and answers: final and non-final. For instance, is the execution behaviour of the system (fully) predictable, i.e. is this behaviour known in all situations? If the answer is yes, then this obviously contributes to the system’s quality. If the answer is no, we may disqualify the system. Then, for example, we may inquire if the real-time system considered is fault-tolerant (see Fig. 3.1). If it is, we may proceed with our questionnaire. In the case of a negative answer, the question remains as to whether the system endangers its environment upon breaking down. If the answer to this is affirmative, then obviously the quality of the system is insufficient and it should not be used. Otherwise we may proceed with additional questions relevant to this issue or with the next topic (e.g. graceful degradation).