When aiming towards user-centred service design, a core issue to the design of “ergonomically correct” service interfaces is their appropriateness with respect to the particular human user behaviour attributes, as they evolve during the utilisation of an interactive service and its constituent applications. The exploitation of human behaviour aspects in the service interaction techniques design process is of significant interest and is presented in this chapter. Though it has been tempting to synthesize many of the presented service design guidelines we prefer to adopt a laundry list-like approach as the materialisation of a service interface design technique heavily depends on a plethora of parameters. In many cases, for the same audience a service implementation needs to be differentiated from other similar services, while in certain other cases this is not part of the recommended actions.
TopInterface Guidelines For The Service Development Process
When aiming towards user-centred design, a central issue to the design of “ergonomically correct” user interfaces is their appropriateness with respect to the particular human behaviour attributes, as they evolve during the utilisation of an interactive service / application. It should be noted that while the physical characteristics of a user might be viewed as static over a limited time span, human behaviour is adaptive and, thus, it might be described as an evolving process that converges to an “equilibrium” state. This state is reached, usually, after an initial period of gradual familiarisation whose duration might vary.
In such a context, the exploitation of human behaviour aspects in the interaction techniques design process is of significant interest. More specifically, the interaction techniques to be supported by the user interface of the demonstrators should meet the interaction requirements of the end users during their gradual and evolving transition from novice users to expert and frequent ones.
According to (Rasmussen, 1981), three classes of behaviour exist, namely skill-based, rule-based and knowledge-based behaviour. The Skills-Rules-Knowledge (henceforth SRK) classification aims to the reduction of human error in the control of complex systems. Reducing human error should be viewed as a problem for the system designer, but of course the designer cannot possibly predict all possible malfunctions and states of a system. SRK suggest a way human operator variability may be viewed at the design stage and is a general description of an operator's mental activities. Above all, SRK is meant to serve as a normative function in guiding the design of displays. At the skill-based level, human performance is governed by stored patterns of preprogrammed instructions represented as analogue structures in a time-space domain. Errors at this level are related to the intrinsic variability of force, space, or time coordination. The rule-based level is applicable to undertaking familiar problems in which solutions are governed by stored rules of the type IF <STATE> THEN <DIAGNOSIS> or IF <STATE> THEN <REMEDIAL ACTION>. Here errors are typically associated with the misclassification of situations leading to the application of the wrong rule or with the incorrect recall of procedures. The knowledge-based level refers to novel situations for which actions must be planned on-line, using conscious analytical processes and stored knowledge. Errors at this level arise from resource limitations and incomplete or incorrect knowledge. With increasing expertise, the primary focus of control moves from the knowledge-based towards the skill-based level; but all three levels can coexist at any one time.
Skill-based behaviour consists of the performance of more or less stored patterns of behaviour, e.g. manual control. One primary characteristic of skill-based behaviour is that no interpretation of the meaning of a display is required; the display must be unambiguous with regard to the required action to take.
Skill-based behaviour refers to highly trained sequences of “automated” behaviour typical for frequently encountered tasks and is a very close coupling between the sensory input and the response action. Skill-based behaviour does not directly depend on the complexity of the task but rather on the level of training and the degree of practice in performing the task. While different factors may influence the specific behaviour of a particular individual, a group of highly trained operators would be expected to perform skill-based tasks expeditiously or even mechanistically with a minimum of mistakes. For the two other classes of behaviour (i.e. rule-based and knowledge-based) the connection between sensory input and output actions is not as direct as in skill-based behaviour.
It should be noted that the borderline between skill-based and rule-based behaviour is fuzzy at times. A keypoint is that what is rule-based for one person can be skill-based for the person who is at such a high state of practice that he can execute a sequence of actions based on a single stimulus. For instance, we classify as skill-based behaviour the performance of well-memorised and frequently rehearsed immediate emergency actions.