Incorporating Unbounded Algorithms into Predictable Real-Time Systems

The incorporation of unbounded components (i.e. software modules that cannot be analysed to produce realistic worst case execution times) into hard real-time applications has been recognised as a key issue for the next generation of systems. We present an system model that caters for the three main approaches to integrating unbounded components --- imprecise computation, sieve functions and multiple versions. This model is feasible because it is supported by schedulability tests that will guarantee the bounded tasks. These test are defined in the paper. A simple computational model that uses preemptive priority-based dispatching is required. The wide-spread use of techniques such as imprecise computation will only happen if they are integrated into standard software engineering methods. We therefore show how the techniques can be realised in Ada 9X. ############### + This work is supported, in part, by the UK Information Engineering Advanced Technology Programme, Grant GR/F 35920/4/1/..