Process Algebra

For systems of sequential agents the fundamental relations between events — causality and conflict — are naturally connected to a global dependency relation on the system's alphabet. Action refinement as a strictly hierarchical approach to system design should preserve this connection. Then it can be guaranteed that also more complex temporal properties of the refined system are inherited from the abstract level. The behaviour of a system of sequential agents is given in terms of synchronisations structures, a location-based subclass of prime event structures. The action refinement operator inherits causality and conflict according to the dependency relation. To express temporal properties of the systems we use vTrPTL, a linear time temporal logic for Mazurkiewicz traces. The logical framework, based on local modalities and fixpoints, allows to define refinement transformation on formulae. Under certain constraints on the refinement function, satisfaction of a formula for the abstract system turns out to be equivalent to satisfaction of the transformed formula for the refined system.

This paper introduces a graphical notation called algebraic state transition diagrams (ASTD), which allows for the combination of state transition diagrams using classical process algebra operators like sequence, iteration, parallel composition, quantified choice and quantified synchronization. It is inspired from automata, statecharts and process algebras. Hence, it combines the strength of all these notations: graphical representation, hierarchy, orthogonality, compositionality, abstraction. Quantification is one of the salient features of ASTDs, because it provides a powerful mechanism for modeling an arbitrary number of instances of an ASTD. A formal operational semantics is given. Our target application domain is the specification of information systems, but ASTDs are presented in a generic manner.

We propose a process algebra, the Algebra of Behavioural Types, as a language for typing concurrent objects in process calculi. A type is a higher-order labelled transition system that characterises all possible life cycles of a concurrent object. States represent interfaces of objects; state transitions model the dynamic change of object interfaces. Moreover, a type provides an internal view of

A fundamental problem in the design and development of embedded control systems is the verification of safety requirements. Formal methods, offering a mathematical way to specify and analyze the behavior of a system, together with the related support tools can successfully be applied in the formal proof that a system is safe. However, the complexity of real systems is such that automated tools often fail to formally validate such systems.

Most recently, the concept of business documents has started to play double role. On one side, a business document (word
processing text or calculation sheet) can be used as specification tool, on the other side the business document is an immanent
constituent of business processes, thereby essential component of business information systems. The recent tendency is that the
majority of documents and their contents within business information systems remain in semi-structured format and a lesser part
of documents is transformed into schemas of structured databases. The semi structured documents can be stored and processed in
the modern database management systems, in compliance with the requirements of business processes. In order to keep in hand
the emerging situation, we suggest the creation (1) a theoretical framework for modelling business information systems; (2) and a
design method for practical application based on the theoretical model that provides the structuring principles. The modelling
approach that focuses on documents and their interrelationships with business processes assists in perceiving the activities of
modern information systems. The interrelationships between documents-centric modelling, the Enterprise Architecture and
systematic approach for design provides an opportunity for a unified modelling.

In this deliverable we introduce ambient LCC, a language to program interaction models for P2P networks. The language is based on process algebra concepts and is specially designed to support the execution of electronic institutions. An algorithm that automatically translates electronic institution specifications into ambient LCC code is presented and illustrated though an example. Background material on electronic institutions, LCC,

In this tutorial we present two major applications of process algebras to performance modelling. Thefirst is the use of classical or timed process algebra to verify simulation models. The second is the directuse of stochastic process algebras to construct and solve performance models. The tutorial presents anoverview of the current trends and areas of active research, as well as their

SUMMARY We have already proposed a process algebra µLOTOS as a mathematical framework to synthesize a process from a number of (incomplete) specifications, in which requirements for the process do not have to be completely determined. It is guaranteed that the synthesized process satisfies all the given specifications, if they are consistent. For example, µLOTOS is useful for incremental design. The advantage of µLOTOS is that liveness properties can be expressed by least fixpoints and disjunctions ∨. In this paper, we present µLOTOS R , which is a refined µLOTOS. The improvement is that µLOTOS R has a conjunction operator ∧. Therefore, the consistency between a number of specifications S1, ··· ,S 2 can be checked by the satisfiability of the conjunction specification S1 ∧ · ·· ∧S2. µLOTOSR does not need the complex consistency check used in µLOTOS.

We develop a 2-categorical theory for recursively defined domains.<br />In particular, we generalise the traditional approach based on order-theoretic structures to category-theoretic ones. A motivation for this development is the need of a domain theory for concurrency, with an account of bisimulation. Indeed, the leading examples throughout the paper are provided by recursively defined presheaf models for concurrent process calculi. Further, we use the framework to study (open-map) bisimulation.