On Modelling and Analysis of Dynamic Reconfiguration of Dependable Real-Time Systems

This paper motivates the need for a formalism for the modelling and analysis of dynamic reconfiguration of dependable real-time systems. We present requirements that the formalism must meet, and use these to evaluate well established formalisms and two process algebras that we have been developing, namely, Webpi and CCSdp. A simple case study is developed to illustrate the modelling power of these two formalisms. The paper shows how Webpi and CCSdp represent a significant step forward in modelling adaptive and dependable real-time systems.Comment: Presented and published at DEPEND 201

An introduction to Biomodel engineering, illustrated for signal transduction pathways

BioModel Engineering is the science of designing, constructing and analyzing computational models of biological systems. It is inspired by concepts from software engineering and computing science. This paper illustrates a major theme in BioModel Engineering, namely that identifying a quantitative model of a dynamic system means building the structure, finding an initial state, and parameter fitting. In our approach, the structure is obtained by piecewise construction of models from modular parts, the initial state is obtained by analysis of the structure and parameter fitting comprises determining the rate parameters of the kinetic equations. We illustrate this with an example in the area of intracellular signalling pathways

One Net Fits All: A unifying semantics of Dynamic Fault Trees using GSPNs

Dynamic Fault Trees (DFTs) are a prominent model in reliability engineering. They are strictly more expressive than static fault trees, but this comes at a price: their interpretation is non-trivial and leaves quite some freedom. This paper presents a GSPN semantics for DFTs. This semantics is rather simple and compositional. The key feature is that this GSPN semantics unifies all existing DFT semantics from the literature. All semantic variants can be obtained by choosing appropriate priorities and treatment of non-determinism.Comment: Accepted at Petri Nets 201

Petri nets for systems and synthetic biology

We give a description of a Petri net-based framework for modelling and analysing biochemical pathways, which uni¯es the qualita- tive, stochastic and continuous paradigms. Each perspective adds its con- tribution to the understanding of the system, thus the three approaches do not compete, but complement each other. We illustrate our approach by applying it to an extended model of the three stage cascade, which forms the core of the ERK signal transduction pathway. Consequently our focus is on transient behaviour analysis. We demonstrate how quali- tative descriptions are abstractions over stochastic or continuous descrip- tions, and show that the stochastic and continuous models approximate each other. Although our framework is based on Petri nets, it can be applied more widely to other formalisms which are used to model and analyse biochemical networks

Structuring and composability issues in Petri nets modeling

Along Petri nets' history, numerous approaches have been proposed that try to manage model size through the introduction of structuring mechanisms allowing hierarchical representations and model composability. This paper proposes a classification system for Petri nets' structuring mechanisms and discusses each one of them. These include node fusion, node vectors, high-level nets, and object-oriented inspired Petri nets extensions, among others. One running example is used emphasizing the application of the presented mechanisms to specific areas, namely to automation systems modeling, and software engineering, where object-oriented modeling plays a major role

Model-based dependability analysis : state-of-the-art, challenges and future outlook

Abstract: Over the past two decades, the study of model-based dependability analysis has gathered significant research interest. Different approaches have been developed to automate and address various limitations of classical dependability techniques to contend with the increasing complexity and challenges of modern safety-critical system. Two leading paradigms have emerged, one which constructs predictive system failure models from component failure models compositionally using the topology of the system. The other utilizes design models - typically state automata - to explore system behaviour through fault injection. This paper reviews a number of prominent techniques under these two paradigms, and provides an insight into their working mechanism, applicability, strengths and challenges, as well as recent developments within these fields. We also discuss the emerging trends on integrated approaches and advanced analysis capabilities. Lastly, we outline the future outlook for model-based dependability analysis

ACP Semantics for Petri Nets

The paper deals with algebraic semantics for Petri nets, based on process algebra ACP. The semantics is defined by assigning a special variable to every place of given Petri net, expressing the process initiated in the place. Algebraic semantics of the Petri net is then defined as a parallel composition of all the variables, where corresponding places hold tokens within the initial marking. Resulting algebraic specification preserves operational behavior of the original net-based specification