A Modeling Methodology for Hierarchical Control Systems and its Application

Current and future computerized systems and infrastructures are going to be based on the layering of different systems, designed at different times, with different technologies and components and difficult to integrate. Control systems and resource management systems are increasingly employed in such large and heterogeneous environment as a parallel infrastructure to allow an efficient, dependable and scalable usage of the system components. System complexity comes out to be a paramount challenge to solve from a number of different points of view, including dependability modeling and evaluation. Key directions to deal with system complexity are abstraction and hierarchical structuring of the system functionalities. This paper addresses the issue of an efficient dependability evaluation by a model-based approach of hierarchical control and resource management systems. We exploited the characteristics of this specific, but important, class of systems and derived a modeling methodology that is not only directed to build models in a compositional way, but it also includes some capabilities to reduce their solution complexity. The modeling methodology and the resolution technique are then applied to a case study consisting of a resource management system developed in the context of the ongoing European project CAUTION++. The results obtained are useful to understand the impact of several system component factors on the dependability of the overall system instance.