Man is still the most extraordinary computer of all.
John F. Kennedy, 21 May 1963
The Human Factors approach is to position the human at the centre of all activities and to consider the human system and interactions from this perspective. An example of a simple model that portrays this is the SHEL concept (Edwards, 1972; Hawkins, 1984). The SHEL concept was named after its components: software, hardware, environment and liveware. The latter, liveware, represented the human. There have been a number of pictorial representations of the SHEL concept as ideas concerning the system resources have been refined. An example of one diagrammatic representation of the model is to place L (for liveware) in the centre of a square surrounded by four other squares (S, H, E, and L) in a symmetrical cross shape. This is shown in Figure 2.1.
A feature of the model was that all five squares were given undulating edges to demonstrate the need to ‘match’ each of the components to the human, i.e. the edges were not deliberately simple or straight. The model also indicates the need to consider human to human communications in system design because liveware appears twice—at the centre and at the edge. This and other similar models (such as the user-centred design model illustrated by Noyes and Baber, 1999:xi) indicate how essential it is to have a sound and thorough understanding of human beings, their capabilities and limitations, both physical and psychological.
The physical aspects relating to the human can be considered in relation to the anatomy and physiology of the human body/system, because these are two key components of Human Factors (see Figure 1.1). Anatomy relates to describing and measuring various dimensions of the body, and includes anthropometry (studying the human when at rest, i.e. static—also referred to as ‘structural’) and biomechanics (studying the human when moving, i.e.