This chart describes common cycles of system definition, in general terms.
System definition is an iterative process as illustrated in the chart. The system is developed in iterations, in which each iteration involves operation disrupted by a critical incidence, followed by investigation. Each iteration has two development sessions:
The definition starts with concept definition and requirements specification. Then, a first version of the system is developed. The definition at this stage is proactive. When ready, the first version is deployed and operation begins.
A critical incidence might instigate an investigation, intended to identify changes in the requirements. The definition at this stage is reactive.
This model applies to common methodologies for system engineering. In general, a critical incidence is any input resulting in a need to change the requirements, such as market changes. This guide is about mitigating the risks of design mistakes, hence, the focus on incidences due to design mistakes.
Updated on 19 Mar 2017.