We propose a language for testing concurrent processes and examine its strength in terms of the processes that are distinguished by a test. By using probabilistic transition systems as the underlying semantic model, we show how a testing algorithm can distinguish, with a probability arbitrarily close to one, between processes that are not bisimulation equivalent. We also show a similar result (in a slightly stronger form) for a new process relation called $-bisimulation-which lies strictly between that of simulation and bisimulation. Finally, the ultimately strength of the testing language is shown to identify a new process relation called probabilistic bisimulation-which is strictly stronger than bisimulation. li? 1991 Academic Press. Inc. 1.

This paper examines how object-oriented extensions to the Petri Net formalism can address a number of issues in the modelling of network protocols. The object-oriented extensions lead to the formalism of Object Petri Nets, with a textual language form referred to as LOOPN++. The paper considers practical examples for which clean, well-structured models can be created because of the support for modularity, inheritance, polymorphism, genericity, and mobile objects.

Peter Sawyer B.Sc. A User Interface Framework for Object-Oriented Database Systems Submitted for the degree of Ph.D. March 1990 Object-oriented database systems (OODBs) provide support for applications which manipulate semantically rich entities of varying granularity. Many existing commercial database systems provide direct manipulation tools which permit users to access database entities and generate applications. Users of OODBs also require sophisticated tools, but the database entities manipulated are of less uniform structure and semantics. The work reported in this thesis has developed a model of a user interface framework for OODBs. The model exploits objects' encapsulation of data (attributes) and operations (methods). It is based on an abstraction from objects to dynamic forms; attributes are represented as fields and methods are represented as graphical buttons. Forms are dynamic because they reflect the functional properties of their underlying objects. A prototype sy...

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