This paper presents a testing-based semantic theory for reasoning about the efficiency of concurrent systems as measured in terms of the amount of their internal activity. The semantic preorders are given an algebraic characterization, and their optimality is established by means of a full abstractness result. They are also shown to subsume existing bisimulation-based efficiency preorders. An example is provided to illustrate the utility of this approach.

This paper presents a testing-based semantic preorder that relates real-time systems given in the process description language TPL on the basis of the predictability of their timing behavior. This predictability is measured in terms of the amount of variability present in processes' "activity-completion times". The semantic preorder is shown to coincide with an already existing, well-investigated implementation relation for TPL-the must-preorder. The optimality of our relation is also established by means of a full abstraction result. An example is provided to illustrate the utility of this work.