Function analysis often leads to a form of function diagram. One basic rule in this work is that it should be free from preconceptions and not bound by any special components or solutions worked out previously. As an example, consider the transport of goods through a supermarket checkout. The question is whether this should be done mechanically or manually with the aid of a conveyor belt for use by the customer or the cashier. This choice should only be made at the function allocation stage, and then only on the basis of certain given criteria (those produced at the goal-setting stage and ergonomic factors are of primary interest in this case). The function analysis must be achieved without prejudice as this is the basis for the resultant allocations being the optimum solutions. The unprejudiced function analysis can then help to create new solutions that are better for mankind.
Thinking without preconceptions is difficult, as it involves having to think in abstractions. When we think, we generally prefer to be concrete. Abstract thought allows us to think about the things we are used to seeing or noticing from a new perspective. If we consider the cleaning of textiles we immediately think of the physical objects that we connect with this task, such as the washing machine, spin drier, or a person in a specific role. But we do not necessarily have to have these components to fulfil the given task in the way stated in the goals. Figure 13.2 shows a simplified function for the task of cleaning textiles.
The various subfunctions needed for the execution of a particular task can each be treated as subtasks with their own criteria and limitations. In this way it becomes easier to think in abstractions, as the tasks and goals are expressed in abstract terms.
In general, it may be said that function analysis should be carried out in as much detail as possible. From the ergonomic point of view, however, it is not desirable to go further than the level determined by the human operator’s inherent method of functioning.
Let us take the hypothetical case where all functions to be defined must be able to be carried out by people (if this is thought to be desirable in the subsequent function allocation process). It will not then be necessary for these functions to be expressed in such detail that it is possible to say beforehand that several different subfunctions must necessarily belong together, for example, for physiological reasons. The visual centre and decision centres in the human brain are, of course, connected. It is therefore meaningless to separate these functions. If it is decided to let the person carry out a visual function, such as identifying the price on an item, the subsequent decision functions (for example, which keys are to be pressed) must also be carried out by a person.
It may be desirable from the technical point of view to carry out a more detailed function analysis after the first allocation of functions. This is because during the choice between the various technical solutions it may be necessary to go into considerably more detail.