Classifying combined hardware/software R models

The need for a combined hardware/software reliability model is increasing day by day; the need is due, among other factors, to increasing software induced hardware failures which endanger system missions. On the other hand, already-developed models have not completely fulfilled this need. In this paper, the relevant literature is reviewed and a classification scheme for reliability models based upon model requirements, users' objectives and other related criteria is given. Some existing models are classified according to this scheme. Finally, from a macro point of view, the statement of the combined system reliability problem is approached, several areas of conflict are identified and some general conclusions are presented which may help to provide a better understanding of the problem and its eventual solution.