Hans-Dieter Ehrich

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We present two logics that allow specifying distributed information systems, emphasizing communication among sites. The low-level logic $\mbox{\sf D}_0$ offers features that are easy to implement but awkward to use for specification, while the high-level logic $\mbox{\sf D}_1$ offers convenient specification features that are not easy to implement. We show(More)
This chapter concentrates on a challenging problem of information system specification and design, namely how to cope on a high level of abstraction with concurrent behaviour and communication as implied by distribution. Since distributed information systems are reactive and open systems maintaining data bases and applications, it is crucial to develop(More)
The development of Programmable Logic Controllers (PLCs) in the last years has made it possible to apply them in ever more complex tasks. Many systems based on these controllers are safety-critical, the certification of which entails a great effort. Therefore, there is a big demand for tools for analyzing and verifying PLC applications. Among the(More)
~ e semantic domain for object-oriented languages and systems outlined in this paper is an amalgamation of two approaches: the objects-as-sheaves approach of the second author published nearly two decades ago, and the more recent ideas of the first and third authors on objects as processes endowed with observation. The basic insight is that objects in the(More)
The envisaged notion of object is presented as corresponding to the basic, universal building block of (information) systems. A simple mathematical model for fully concurrent objects (actors) is adopted that extends a suitable model for sequential processes. An object is defined as a process possibly endowed with initiative and tracedependent attributes.(More)
In this paper, we present the use of Troll for the conceptual modelling of distributed information systems. Troll offers both textual and graphical notations. Troll has been used in practice to model an industrial information system. We use an extract of this case study to describe briefly the syntax and underlying semantics of the language. We also show a(More)