Semantics of finite and infinite networks of concurrent communicating agents

A language for describing finite and infinite networks of loosely coupled, concurrent, nondeterministic, communicating agents is introduced. To every program a finite or infinite graph (network) is related representing graphically the communication structure of the described system. A denotational semantics is defined based on fixed point theory. Algebraic laws for the networks are studied that allow to transform them without changing their denotational meaning. Following the increasing complexity of denotational models for stream-processing networks a hierarchy of five languages is treated: first a language of finite, deterministic networks, then infinite (i.e., recursively defined), deterministic ones, then nondeterministic finite and nondeterministic infinite networks with free choice merge. Finally we study a language including fair, nonstrict merge. Manfred Broy finished his studies with the Diplom in Mathematics and Computer Science at the Technical University of Munich. Till 1983 he was research and teaching assistant at the Institut für Informatik and the Sonderforschungsbereich 49 «Programmiertechnik». At the Technical University of Munich he also did his Ph.D. (in February 1980 with the subject: «Transformation parallel ablaufender Programme») and qualified as an university lecturer (in 1982 with the subject: «A Theory for Nondeterminism, Parallelism. Communication and Concurrency»). March 1982 he spent as a Visiting Professor at the University Paris Sud. Since April 1983 he has been Full Professor for Computer Science at the Faculty of Mathematics and Computer Science at the University of Passau. His fields of interest are: Programming languages, program development and distributed systems.     

Erfolgreiches Management von Software-Projekten

Für Unternehmen der unterschiedlichsten Branchen ist hohe Produktivität und Qualität bei der Entwicklung betrieblicher Informationssysteme von strategischer Bedeutung.     

Specification and design of shared resource arbitration

The specification, modular design and verification of distributed communicating systems is demonstrated by an example. The scheduling of the access to a common shared resource by a finite number of devices with priorities is a well known problem from hardware and operating systems design. Using the concepts of stream processing continuous function a variety of formal requirement and design specifications for this problem are given and the design specifications are proven correct w.r.t the requirement specifications. From the design specifications one can immediately read off applicative programs implementing the requirement specifications. Special attention is paid to the aspect of modelling time.     

A systematic approach to language constructs for concurrent programs

Several styles and notations for representing concurrent programs are shortly explained and related to each other. It is basically demonstrated how the different language concepts found in concurrent programming conceptually evolve from classical styles of functional and applicative programming.     

Partial abstract types

Summary Hierarchical abstract types, where particular sorts, operations, and axioms are designated as primitive, with conditional equational formulas are studied. Introducing notions of different homomorphisms particular models of this class can be distinguished as initial or (weakly) terminal. Sufficient conditions for the existence of such models are given and their relationship to the principle of fully abstract semantics is investigated. By this the concept of algebraic specification is extended to specify the semantics of programming languages in a completely abstract algebraic way as it is demonstrated for two toy languages.This research has been partially sponsored by the Sonderforschungsbereich 49 — Programmiertechnik, München