Abstract. This paper examines the influence of the Raf Kinase Inhibitor Protein (RKIP) on the Extracellular signal Regulated Kinase (ERK) signalling pathway [5] through modelling in a Markovian process algebra, PEPA [11]. Two models of the system are presented, a reagentcentric view and a pathway-centric view. The models capture functionality at the level of subpathway, rather than at a molecular level. Each model affords a different perspective of the pathway and analysis. We demonstrate the two models to be formally equivalent using the timingaware bisimulation defined over PEPA models and discuss the biological significance. 1

Abstract. Considering functional correctness and performance evaluation in a common framework is desirable, both for scientific and economic reasons. In this paper, we describe how the Cadp toolbox, originally designed for verifying the functional correctness of Lotos specifications, can also be used for performance evaluation. We illustrate the proposed approach by the performance study of the Scsi-2 bus arbitration protocol. 1

Numerous formal specification methods for reactive systems have been proposed in the literature. Because the significant differences between the methods are hard to determine, choosing the best method for a particular application can be difficult. We have applied several different methods, including Modechart, VFSM, ESTEREL, Basic LOTOS, Z, SDL and C, to an application problem encountered in the design of software for AT&T's 5ESS telephone switching system. We have developed a set of criteria for evaluating and comparing the different specification methods. We argue that the evaluation of a method must take into account not only academic concerns, but also the maturity of the method, its compatibility with the existing software development process and system execution environment, and its suitability for the chosen application domain.

This paper aims at demonstrating the benefits and importance of the service concept in the model-driven design of distributed applications. A service defines the observable behaviour of a system without constraining the system’s internal structure. We argue that by specifying application-level interaction aspects as a service, and designing application parts in terms of this service, the design of application parts is not constrained by interaction patterns provided by a middleware platform. Therefore, a level of platform-independence can be achieved, so that the design of application parts can be reused across a large set of middleware platforms. The service concept is also used in our approach to describe an abstract platform that defines what characteristics of a potential target middleware platform are considered in platform-independent design. We discuss the trade-offs a platform, and discuss alternatives for platform-specific realization.

. We present a simple method to associate rewards with terms of the stochastic process algebra EMPA in order to make the specification and the computation of performance measures easier. The basic idea behind this method is to specify rewards within actions of EMPA terms, so it substantially differs from methods based on modal logic. The main motivations of this method are its ease of use as well as the possibility of defining a notion of equivalence which relates terms having the same reward, thus allowing for simplification without altering the performance index. We prove that such an equivalence is a congruence finer than the strong extended Markovian bisimulation equivalence, and we present its axiomatization. 1 Introduction A commonly used method to specify steady-state performance measures for Markovian models is based on rewards [6]. The basic idea is that a number describing a reward (or weight) is attached to every state of the Markovian model, and the performance index is de...

This paper presents some basic design concepts for the design of open distributed systems. These concepts should form the basis for the development of effective design methodologies. The paper discusses how design concepts, such as interaction, action and causality relation, can be used for modelling and structuring behaviours of functional entities in a distributed environment. The paper also addresses some consequences of the application of these design concepts such as the choice of language elements and operations to represent behaviour structure, the structuring of the design process, and the definition of design operations for behaviour refinement.

Abstract. The software application domain of customer-oriented telephony is worth the attention of specialists in formal methods. Primarily this paper is a tutorial about customer-oriented telephony. It also includes observations about how this domain should be formalized, including critiques of some popular approaches. 1.

This paper proposes design concepts that allow the conception, understanding and development of complex technical structures for open distributed systems. The proposed concepts are related to, and partially motivated by, the present work on Open Distributed Processing (ODP). As opposed to the current ODP approach, the concepts are aimed at supporting a design trajectory with several, related abstraction levels. Simple examples are used to illustrate the proposed concepts.

Methods are needed to help using formal specifications in a practical way. We herein present a method for the development of mixed systems, i.e. systems with both a static and a dynamic part. Our method helps the specifier providing means to structure the system in terms of communicating subcomponents and to give the sequential components using a semi-automatic concurrent automata generation with associated algebraic data types. These components and the whole system may be verified using common set of tools for transition systems or algebraic specifications. Furthermore, our method is equipped with object oriented code generation in Java, to be used for prototyping concerns.

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