as well as the dialogue level will be covered。 The corresponding submodules of advanced interfaces will more often tend to contain knowledge-based subfunctionalities。 Also, some of the decision support functionalities may be implemented directly in the human-machine interface, rather than in the advanced automated technical system (Johannsen, 1994)。

A closer look at these issues is necessary to identify the main functionalities of human-machine interfaces and leads to the definition of alternative paradigms。 

Both functionalities and paradigms will be explained in the following section。 The design of human-machine interfaces and of their submodules is a highly creative task which requires a lot of knowledge in many different disciplines (Rouse and Cody, 1988; Johannsen, 1990)。 The design process itself will be viewed in the third section of this paper as a problem-solving task with a multitude of alternative options。

The fourth section deals with concepts and examples of knowledge-based support for the design process of human-machine interfaces。 The overall concept of the knowledge-based support for the human interface designer assumes that a goal structure for a particular human-machine system had already been set up and that the function allocation between its technical system and the human operators had been accomplished, too。 An alternative but more complicated approach could combine the design of the human-machine interface with the design of the knowledge-based decision support systems for the human operators。 Here, only the visualisation form of the presentation level and the dialogue level have to be designed。 For this purpose, several knowledge modules for supporting the designer are proposed。

2。 Functionalities and Paradigms of Human-Machine Interfaces

A general specification of Human-Machine Interface (HMI) functions has to be derived。 As Fig。 2 indicates, the function specification for the human-machine interfaces depends on the goals and goal structures prescribed for the human-machine system, on all kinds of technological and intellectual means for accomplishing these goals, and on the tasks to be performed by the human operators with the purpose of achieving the goals by appropriate usage of the available means。

The overall goals of the human-machine system are mainly (1) productivity goals, (2) safety goals, (3) humanisation goals, and (4) environmental compatibility goals。 An appropriate goal structure needs to be specified in which these four goal classes are related to each other and further subpided into several hierarchical levels of subgoals。 The productivity goals include economic as well as product and production quality goals。 The importance of the safety goals is strongly influenced by the application domain。 This goal class dominates all others in many large-scale systems and, particularly, in risky systems。 The environmental compatibility goals refer to the consumption of energy and material resources as well as to impacts on soil, water, and air。

The humanisation goals comprise team and work organisation, job satisfaction, ergonomic compatibility, and cognitive compatibility。 The latter includes the subgoals of transparency and human understanding。

The means for achieving the goals can be separated into purely technological means and human-related means。 Most issues concerned with the design of the technical process itself are purely technological means。 The degree of automation also seems to belong to this category。 However, it also represents human-related means, because my decision for a particular supervision and control system prescribes tasks to be performed by the human operators。 Thus, the supervision and control systems and, even more, the knowledge-based decision support systems should be designed with a human-centred approach considering human-related means。

The human-related means comprise several issues。 Knowledge about the application domain as well as about human operator's needs and strategies can be regarded as human-related means。 This may be described by structural, functional, causal, and cognitive relationships。 Other human-related means are available through different views of the application domain。 These views consider the levels of abstraction, the levels of aggregation or detail, parallel versus serial presentation, navigational possibilities, and degrees of coherence。 All these means are implicitly inherent in the application domain but often need to be transformed for explicit usage。