HRA — The First Generation

This chapter gives a synoptic view of nine different first-generation approaches to HRA to explain and represent some of the most frequently used techniques in current times. The purpose of this chapter, however, is to characterize and not identify which approaches are better (or worse) than the others, but rather to characterize them in terms of a common frame of reference. That frame of reference is the MCM framework. Each of the nine HRA approaches is thus characterized with respect to the classification scheme it employs, the explicitness of the method, and the characteristics of the underlying operator model in terms of method descriptions (all of the survey approaches are fairly explicit, mainly because they have all been developed in answer to practical needs). None of the recognized HRA approaches seems to have developed from a theoretical or “academic” basis, which means that few of them show significant connections between the method and the classification schemes; indeed, very few of them include a well-defined classification scheme. It nevertheless represents a clear recognition of what the basic problems are, and indicates that the solution must be an approach that addresses all issues at the same time.