On the Reliability Analysis of Systems and SoS: The RAMSAS Method and Related Extensions

This paper aims at contributing to fill the lack of methods specifically conceived for addressing the analysis and verification of nonfunctional requirements. In particular, the attention is focused on system reliability, which is a key requirement to be satisfied particularly for mission-critical systems where system failures could cause even human losses. To this end, this paper presents an up-to-date version of RAMSAS, which is a recently proposed model-based method for the reliability analysis of systems through simulation. The present version of RAMSAS is the result of an intensive experimentation phase in several application domains (avionics, automotive, and satellite) that allowed for the improvement of the effectiveness of the method, particularly in the modeling of both the intended and dysfunctional system behaviors. Moreover, this paper discusses the specific issues that arise when moving from the reliability analysis of systems to that of systems of systems (SoSs) and proposes a possible extension of the RAMSAS method (called RAMSoS) that is able to address the identified issues and thus support the reliability analysis of SoSs through simulation.