Using system architecture considerations to analyze allocation of functions

摘要

A number of methods exist for analysing 'Allocation of Functions' (AoF) from a Human Factors Engineering (HFE) perspective (e.g., Fitts List [1]). These methods have been criticised as being of limited practical value in a design and engineering sense. In particular, the fundamental assumption that AoF is a discrete and orderly part of system design, or can be separated from lower-level considerations of how a system function is executed in practice, has been challenged [2]. In response to the priority placed on AoF by nuclear industry regulators and the apparent shortfalls in existing approaches, this paper presents how approaches from Systems Engineering Architecture Description (AD) can be used to address AoF difficulties. AD is defined as the "fundamental organisation of a system, embodied in its components, [and] their relationships to each other and the environment" [3]. An AD representation of a system is expressed as a set of interlinked models. The intention being that the goals, functions, and relationships can be captured and used as aids for discussion and change. By considering the elementary properties of each function, and their structure and relationships as shown via AD views, the following questions can be considered: (1) Is the allocation of a function to a particular system actor compatible with the strengths of that actor? (2) Do transitions between system functions introduce any adverse effects? (3) Does the set of functions allocated to a particular system actor form a coherent grouping? The AD-orientated approach has been encouraging as it is more closely aligned with modern systems engineering practice. Further work to verify the outputs of the method against existing facilities and designs is proposed.