Issues in building dynamic real-time systems

The issues involved in building dynamic, hard real-time systems, in which resource availability and requirements are not fixed, are discussed. It is shown that the problem of ensuring timing correctness in dynamic real-time systems has three aspects: resource requirements, resource availability, and guarantees. These issues overlap, and a single mechanism or technique may address several issues. The R-Shell, an object-oriented framework that structures resources in a class hierarchy so that they can be selected or substituted dynamically is described.<>