Separating Concerns in Requirements Analysis: An Example

Often, a requirements document is structured as a long list of individual ”requirements”, each describing an anticipated function or user interaction. An alternative approach is to identify a collection of subproblems, each representing an aspect of the larger problem, and to describe each subproblem in isolation, deferring their composition to a later stage. This paper illustrates the approach by applying it to the requirements of the positioning functions of a proton therapy installation. It explains how a flaw in the design of the system can be isolated to a single subproblem, which can be formalized and subjected to automatic analysis.