INTEGRATING OPTIONAL SOFTWARE COMPONENTS INTO HARD REAL-TIME SYSTEMS

The incorporation of optional components (i.e. software modules that c annot be analysed to produce realistic worst case execution times) int o hard real-time applications has been recognised as a key issue for t he next generation of real-time systems. A system model is presented t hat caters for the three main approaches to integrating optional compo nents: milestone methods, sieve functions and multiple versions. The f ormal language TAM is used to describe this model. Further, an approac h to ensuring that the mandatory components of this model are guarante ed to meet their deadlines is described, and the optional components a re admitted for scheduling such that the utility of the system is maxi mised.