for example, an experienced employee who operates a five-axis machining center in a shop environment may take a two-week vacation. Her temporary replacement may be less experienced.this change in one component of the system (person/host) increases t pro Such a simple example is easily understood. However. ns of are this simple. Some are so subtle quire a team of people, each with a different type of ex primary components of the systems model are the pers nt. information. decisions. risks. and the task to be perfor nents has a bearing on the probability that an accident model is illustrated in Figure 3-5