ABSTRACT
In recent years, the scope of human factors (HF) involvement in interactive system2 development has become wider. For instance, increasing emphasis is placed on earlier and continued HF input throughout the design cycle (see Moraal and Kragt, 1990; Lundell and Notess, 1991). Hence, HF contributions are targeted not only at design evaluation, but also at design specification and implementation. Although designers are increasingly aware of the need for wider HF involvement, appropriate incorporation of its inputs remains hindered by notational inadequacies. In particular, the demands associated with design specification, namely the format, granularity and specificity of design descriptions, have not been satisfied by existing HF notations. This requirement for better notations is also implicated by the following observations in recent reports:
(a) current HF specifications are insufficiently specific to support design collaboration between HF designers and software engineers. This situation is aggravated further by the development of
increasingly complex and sophisticated interactive systems. For instance, in the context of safety critical system development, task specifications have to be detailed enough to support design simulation, workload assessment and probabilistic human reliability assessment Thus, Brooks (1991) emphasised that task specifications should describe the hierarchical structure and operational control of the user’s task. Consequently, it follows that more powerful notations need to be developed to support more specific design specification;
(b) the uptake of HF may be hindered by inadequate guidance on the process of design derivation. Specifically, HF has been criticised for focusing predominantly on what should be done and not on how design requirements could be met (Sutcliffe, 1989). The imbalance in focus may be an artefact of the traditionally late recruitment of HF to design. To rectify the problem, wider and more explicit conceptions of the HF design process have been defined and developed into structured methods (see Blyth and Hakiel, 1989; Damodaran, Ip and Beck, 1988; Lim, Long, and Silcock, 1992; Sutcliffe, 1988). As a result, existing notations have been enhanced to accommodate the specification of a wider range of intermediate HF design products. The notations described in this paper are a product of such developments.
