The paper illustrates the use of structured notations to support the specification of various aspects of a system design; such as organisational hierarchies, conceptual level tasks, domain semantics, human-computer interactions, etc. In contrast with formal or algebraic notations, graphical structured notations are communicated to users more easily. Thus, user feedback elicitation and design validation would be supported better throughout system development. It is expected that the structured notations illustrated in the paper, could be used more widely for two reasons; namely they support more specific task specifications, and have now been incorporated into a structured human factors method. In addition, off-the-shelf computer-based support for the notation is emerging, e.g. PDFTM.

Keywords: graphical structured notations, human factors specifications, structured human factors method.

General Requirements of a Notation for Human Factors Specification

Generally, an appropriate human factors notation should fulfil two pre-requisites, namely it should rectify the inadequacies of existing human factors notations, and accommodate additional specification demands arising from wider human factors involvement in system development. In particular, a notation should satisfy the following requirements:

1. a. Specificity. Current human factors specifications have been criticised for being insufficiently specific. This situation is aggravated further by the increasingly complex and sophisticated systems being designed. In response to these demands, human factors methods should be enhanced to include more powerful notations to support tighter design specification. For instance, in safety critical system development, task specifications should be detailed enough to support design simulation, workload assessment and probabilistic human reliability assessment. Thus, Brooks' (1991) emphasis on task specifications that reveal the hierarchical structure and operational control of the user's task, is especially pertinent. Hence, notational constructs should satisfy the demands of such design specifications;

2. […]