Introducing Needs and Requirements

This section introduces the key concept of Needs and discusses the different types that Needs exist, such as Requirements, Capabilities, and Goals. We will discuss the importance of defining the exact meaning of the terminology, and the MBSE Ontology that has been developed throughout this book so far will also be expanded upon to introduce these new concepts. We will start by looking at what Needs actually are…

Defining Needs

One of the most important concepts associated with Systems Engineering is that of the Need, as shown in the following diagram:

Figure 6.1: Ontology Definition View showing basic Needs

The diagram in Figure 6.1 shows an Ontology Definition View that introduces the concept of a Need and its relationship to a System, which is visualized using a SysML block definition diagram.

The diagram shows that one or more Needs describe the purpose of one or more Systems. The concept of a Need is important...