Two diierent formalisms for concurrency are compared and are shown to have common foundations. The Input/Output automaton model and the theory of testing are analyzed in the framework of transition systems. The relationship between the fair and quiescent preorders of I/O automata is investigated and the two preorders are shown to coincide on a large class of automata. I/O automata are encoded i...

This paper presents a testing-based semantic preorder for reasoning about the predictability of realtime systems specified using the process description language TPL. The predictability of the systems is measured in terms of the amount of variability present in their “activity-completion times”. The semantic preorder is shown to coincide with an already existing, well-investigated implementatio...

We propose a new approach for automatic verification of programs with dynamic heap manipulation. The method is based on symbolic (backward) reachability analysis using upward-closed sets of heaps w.r.t. an appropriate preorder on graphs. These sets are represented by a finite set of minimal graph patterns corresponding to a set of bad configurations. We define an abstract semantics for the prog...

We present a simulation preorder for reactive systems modeled by fair Kripke structures whose transition relation is divided into two parts, internal and external. The first one models the internal behaviour of the system, while the second one is used to model the interaction with an environment. We show that our simulation preorder preserves a substantial subset of ∀CTL∗. Then, we present an a...

Consider the following curious puzzle: call an n-tuple X = (X1, . . . , Xn) of sets smaller than another ntuple Y if it has fewer unordered sections. We show that equivalence classes for this preorder are very easy to describe and characterize the preorder in terms of the simpler pointwise inclusion and the existence of a special increasing boolean operator f : B → B. We also show that contrary...

A testing scenario in the sense of De Nicola and Hennessy is developed to measure the worst-case eeciency of asynchronous systems using dense time, and it is shown that one can equivalently use discrete time. The resulting testing-preorder is characterized with some kind of refusal traces. Furthermore, the testing-preorder is reened to a precongruence for standard operators known from process a...

We consider decidability questions for simulation preorder (and equivalence) for processes generated by one-counter machines. We sketch a proof of decidability in the case when testing for zero is not possible, and demonstrate the undecidability in the general case.

TACS is an extension of CCS where upper time bounds for delays can be specified. Lüttgen and Vogler defined three variants of bismulation-type faster-than relations and showed that they all three lead to the same preorder, demonstrating the robustness of their approach. In the present paper, the operational semantics of TACS is extended; it is shown that two of the variants still give the same ...