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We present a broad extension of the conventional formalism of state machines and state diagrams, that is relevant to the specification and design of complex discrete-event systems, such as multi-computer real-time systems, communication protocols and digital control units. Our diagrams, which we call statecharts, extend conventional state-transition(More)
While message sequence charts (MSCs) are widely used in industry to document the interworking of processes or objects, they are expressively weak, being based on the modest semantic notion of a partial ordering of events as defined, e.g., in the ITU standard. A highly expressive and rigorously defined MSC language is a must for serious, semantically(More)
We describe the semantics of statecharts as implemented in the STATEMATE system. This was the first executable semantics defined for the language and has been in use for almost a decade. In terms of the controversy around whether changes made in a given step should take effect in the current step or in the next one, this semantics adopts the latter approach.
Among the many approaches to formal reasoning about programs, Dynamic Logic enjoys the singulax aclv~ntage of being strongly related to classical logic. Its variants constitute natural generalizations and extensions of classical formalisms. For example, Prepositional Dynamic Logic (PDL) can be described as a blend of three complementary classical(More)
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(More)
The higraph, a general kind of diagramming object, forms a visual formalism of topological nature. Higraphs are suited for a wide array of applications to databases, knowledge representation, and, most notably, the behavioral specification of complex concurrent systems using the higraph-based language of statecharts.
This paper reports on an effort to develop an integrated set of diagrammatic languages for modeling object-oriented systems, and to construct a supporting tool. The goal is for models to be intuitive and well-structured, yet fully executable and analyzable, enabling automatic synthesis of usable and efficient code in object-oriented languages such as C++.(More)
This paper is an attempt at laying the foundations for the classification of queries on relational data bases according to their structure and their computational complexity. Using the operations of composition and fixpoints, a Σ-Π hierarchy of height, ω2, called the fixpoint query hierarchy, is defined, and its properties investigated.(More)
The concept of “reasonable” queries on relational data bases is investigated. We provide an abstract characterization of the class of queries which are computable, and define the completeness of a query language as the property of being precisely powerful enough to express the queries in this class. This definition is then compared with other proposals for(More)