Combining specification methods for distributed systems

This thesis summarizes the theoretical results of a research project at Siemens ZT that aimed at supporting the use of formal methods in the design of distributed systems. The speci cation language UNITY formed the starting point of the investigations. However, UNITY had to be extended with additional language and structuring concepts in order to deal with realistic industrial case studies. These extensions allow the description of distributed systems as set of properly instantiated modules that communicate using both synchronous actions and shared variables. The speci cations may be represented in a UNITY-like notation, but also as ! -automata or in linear temporal logic. The choice of these three speci cation methods resulted from the observation of their supplementing advantages: the textual notation allows the concise and intuitive description of large systems. Automata are best suited for connecting simulation and veri cation tools. If the automata are nite then properties may be proven using model checking, and the automata may serve as visualization. The logical representation enables the user to describe both the speci cations and their properties in a uniform formalism. The main goal of the thesis is to formally demonstrate that these speci cation methods may be used in parallel. In order to reach this goal a standardization proved to be useful in order to be able to directly express the elementary language constructs in all methods. This is achieved by appropriate extensions for the methods. For example, it is possible to describe assumptions concerning the environment directly in the textual notation, as well as to express fairness for automata and synchronous actions in the logic. Textual speci cations can be translated to both the extended automata and the extended logic. Both translations can be proven to result in the same set of observable behavior in terms of traces. In addition to modular and hierarchical speci cations, two concepts showed to be useful to deal with realistic examples: parameterization and the extraction of nite models directly from the textual notation. Control systems serve as a typical example for distributed systems. They are built up from the base automation that traditionally is data ow-oriented and the event-oriented high level process control. By means of a case study it is nally shown, that the proposed speci cation language is suited equally for the base automation and the high level process control. Ich hatte das Gl uck, zur Erstellung dieser Arbeit mit einem Doktorandenstipendium der Siemens AG unterst utzt zu werden, f ur dessen Gewahrung ich Herrn Prof. B uttner meinen herzlichen Dank aussprechen mochte. In der Fachabteilung ZT SE 4 fand ich eine fachlich anregende Arbeitsumgebung, in der ich mich sehr wohl gef uhlt habe. Neben meinen M unchnern und Erlangern Kollegen danke ich dabei auch den Gastwissenschaftlern und Werkstudenten, die das Projekt TLT begleitet haben. Den Gutachtern, Herrn Prof. Schmitt und Herrn Prof. Rischel, danke ich f ur das meiner Arbeit entgegengebrachte Interesse und f ur die hilfreichen Anregungen. Zu guter Letzt von ganzem Herzen ein K u chen f ur Karla.