ABSTRACT
This chapter characterises the variability of the functions that constitute the Functional Resonance Analysis Method (FRAM) model. It addresses both the potential variability, referring to the model, and the expected actual variability, referring to an instantiation of the model. In the FRAM, the characterisation of performance variability is needed to understand how functions can become coupled and how this can lead to unexpected outcomes. The variability of a function may, of course, also be due to combination of the three conditions are internal variability, external variability and upstream-downstream coupling. One way of characterising variability is to distinguish among different types of functions, for instance technological functions, human functions and organisational functions. The simple solution to describe the consequences of performance variability is to note that the Output from a function can vary in terms of timing and precision. The FRAM model describes the possible couplings between functions, and is therefore also the basis for describing the potential variability of functions.
