This paper provides a brief overview of the STATEMATE system, constructed over the past three years by i-Logix Inc., and Ad Cad Ltd. STATEMATE is a graphical working environment, intended for the specification, analysis, design and documentation of large and complex reactive systems, such as real-time embedded systems, control and communication systems, and interactive software. It enables a user to prepare, analyze and debug diagrammatic, yet precise, descriptions of the system under development from three inter-related points of view, capturing, structure, functionality and behavior. These views are represented by three graphical languages, the most intricate of which is the language of statecharts used t o depict reactive behavior over time. In addition to the use of statecharts, the main novelty of STATEMATE is in the fact that it 'understands' the entire descriptions perfectly, to the point of being able to analyze them for crucial dynamic properties, to carry out rigorous animated executions and simulations of the described system, and to create running code automatically. These features are invaluable when it comes to the quality and reliability of the final outcome.Reactive systems (see [P, HP]) are characterized as owing much of their complexity to the intricate nature of reactions to discrete occurrences. The computational and continuous parts of such systems are assumed to be dealt with using other means, and it is their reactive, control-driven parts that are considered here t o be the most problematic. Examples of reactive systems include most kinds of real-time computer embedded systems, rontrol plants, communication systems, interactive software of varying nature, and even VLSI circuits. Common t o all of these is the notion of reactive behavior, whereby the system is not adequately described by a simple relationship that specifies outputs as a function of inputs, but, rather, inquires relating outputs t o inputs through their allowed combinations in time. Typically, such descriptions involve complex sequences of events, actions, conditions and information flow, often with explicit timing constraints, that combine to form the system's overall behavior.It is fair t o say that the problem of finding good methods to aid in the development of such systems has not been satisfactorily solved. Standard structured design methods do not adequately deal with the dynamics of reactive systems, since they were proposed to deal primarily with non-reactive, datadriven applications, in which a good functional decomposition and data-flow description are sufficient. As to commercially available tools for real-time system design, most are, by and large, but sophisticated graphics editors, in which one can model certain aspects of reactive systems but in which a user can do little with the resulting descriptions beyond testing them for syntactic consistency and completeness and producing various kinds of output reports. These systems are often helpful in organizing a designer's thoughts and in communicating those thou...

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With the (necessary) condition that atomic programs in process logic (PL) be binary, we present an algorithm for the translation of a PL formula p into a program '(p) of propositional dynamic logic (PDL) such that a finite path satisfies pitt it belongs to '(p). This reduction has two immediate corollaries: 1) validity in this PL can be tested by testing validity of formulas in PDL; 2) all state properties expressible in this PL are expressible in PDL. The translation, however, is of nonelementary time complexity.The significance of the result to the search for natural and powerful logics of programs is discussed.Key words, process logic, propositional dynamic logic, temporal logic 1. Introduction. The formalism of dynamic logic [Prl] has been successfully proposed as a unifying framework for the formal reasoning about programs. It generallogic, enjoying the advantages of both. Pratt's original process logic [Pr2], Parikh's SOAPL [PA] and Nishimura's language IN], were preliminary efforts in this direction. A recently proposed system which seems to have unified the basic concepts of both dynamic and temporal logic is the system of process logic (PL) presented in [HKP]. It borrows the program constructs and modal operators and from dynamic logic, and the temporal connectives t and sut from temporal logic and combines them into a single system.The declared purpose of this new system is to enable compositional reasoning about continuous behavior of programs. As such, one would expect it to be able to express properties on the propositional level inexpressible by either PDL or TL, the propositional versions of dynamic and temporal logic, respectively. Indeed, the PL expression [a]somep, for example, states that in every execution of the program there must be at least one state satisfying p. It can be shown [HI that this property cannot be expressed in PDL. If p is some property of a second program, say then it is not expressible in TL either.Having demonstrated this greater expressibility, PL certainly becomes an attractive system for study. It is shown in [HKP] that validity in (the propositional version of) PL is decidable by reduction to SnS, the second order theory of n successors JR]. This yields a nonelementary decision procedure in general, and it is still unknown whether an alternative elementary decision procedure exists. It has also been shown that various small extensions to the system lead to undecidability [CHMP], IS]. So much for