A component based approach to evaluate the system availability

Considering the current technological developments in an automated system, the design phase is of increasingly importance. Indeed, a lot of constraints have been taken into account, and it becomes necessary at each step of the design to be able to give the best evaluation of the possibilities of operation and dependability of the system. Means to obtain results in a qualitative way of these parameters without many calculations are essential. In this paper, we propose to evaluate the system availability by a component-based approach with a qualitative way, which leads on reconfiguration ability of the system. The utilized model is based on the notion of services provided by the system components and the representation of the high level services of the system into an AND/OR tree. The research of the minimal cuts of this tree allows determining the minimal hardware resources of the system and the definition of an index of partial reconfiguration. These information give to the designers a good evaluation of the operation of the system and the continuity of running when a failure occurs on a component before the setting up of the system. The two tanks system is used to illustrate the proposed approach.