Deriving real-time requirements for software from safety analysis

One of the main problems in industrial applications of computer systems is software safety, i.e. question if software can contribute (often indirectly, through a long chain of intermediary events) to an accident. Adequate identification and definition of safety requirements is crucial for safety-critical software systems. The paper presents a systematic way of derivation of software safety requirements based on a formalised model of fault trees. The approach is demonstrated through a case study. The presented approach is particularly focused on timing requirements for software which result from the safety analysis performed for the whole application.