Sune Wolff

Collaborative modelling and co-simulation in the development of dependable embedded systems

This paper presents initial results of research aimed at developing methods and tools for multidisciplinary collaborative development of dependable embedded systems. We focus on the construction and analysis by cosimulation of formal models that combine discrete-event specifications of computer-based controllers with continuous-time models of the environment with which they interact. Basic concepts of collaborative modelling and co-simulation are presented. A pragmatic realisation using the VDM and Bond Graph formalisms is described and illustrated by means of an example, which includes the modelling of both normal and faulty behaviour. Consideration of a larger-scale example from the personal transportation domain suggests the forms of support needed to explore the design space of collaborative models. Based on experience so far, challenges for future research in this area are identified.

Deploying Co-modelling in Commercial Practice

We present observations on the initial industrial deployment of collaborative modelling and co-simulation technology using the Crescendo tools. We asked the practitioners who had undertaken the studies to comment on how the approach differed from or could be integrated with current practice, how resources were distributed, and what challenges and benefits were encountered in the process. Key observations included the value of extra time expended in early development stages being recovered later, the reduced need for physical prototypes, importance of stable and usable tools, and the need for processes to coordinate the production of co-models.

Methods for Creating Co-models of Embedded Systems

In developing an embedded system by multidisciplinary co-modelling, the choice of modelling process is at least as important as the technical decisions made in the co-models themselves. We here present several alternative routes to the development of a first working co-model, and suggest criteria for their selection based on characteristics based on features of the problem and its decomposition, and by pragmatic concerns such as the relative development risks of the system elements. We demonstrate the use of SysML to provide early clarity on the purpose of modelling and suggest structural decompositions, and illustrate the approaches on two case studies.