Abstract

Abstract
In this paper, we describe an approach to allocation of function that makes use of scenarios as its basic unit of analysis. Our use of scenarios is driven by a desire to ensure that allocation decisions are sensitive to the context in which the system will be used and by insights from economic utility theory. We use the scenarios to focus the attention of decision makers on the relative costs and benefits of developing automated support for the activities of the scenario, the relative impact of functions on the performance of the operator's primary role and on the relative demands placed on an operator within the scenario. By focussing on relative demands and relative costs, our method seeks to allocate the operator's limited resources to the most important and most productive tasks within the work system, and to direct the effort of the design organization to the development of automated support for those functions that deliver the greatest benefit for the effective operation of the integrated human-machine system.

Abstract
Usability problems associated with virtual environments are a serious obstacle to their successful development. One source of these problems is that virtual environment toolkits provide only a small number of predefined interaction techniques that are expected to be used regardless of context, hence developers are not encouraged to consider interaction. In addition, there are no generally accepted development methodologies for virtual environments. Therefore, even when developers do consider interaction, it is likely to be in an ad hoc fashion driven by technology rather than requirements. If virtual environments are to be useful in a wider context, it is important to provide developers with methods (and tools to support the methods) by which interaction techniques can be systematically designed, tested and refined. In this paper we present the Marigold toolset which supports such a development process. The process begins with a visual specification of the technique being designed. This is requirements centred because it abstracts from implementation issues. Using the toolset, this specification is refined to a prototype implementation so that the technique can be explored in the context of the other elements of the environment. In this way, the developer can verify the technique against requirements in both the specification and prototype. Additionally, because the specification is readily understandable, users can be involved at both stages of the process.

Abstract

Abstract
In this paper, we consider the concept of the impact of an action or human error. We begin from an informal definition of impact as: • the effect that an action or sequence of actions has on the safe and successful operation of a system; • and develop a quantitative measure of the impact of specified behaviours. It is important that human-machine interface designers should understand the relationship between operator actions and the hazards associated with a system. We demonstrate how impact can be assessed prior to, or in parallel with, the design of the human-machine interface, and show how impact assessments could be used to allow risk analysts to inform designers about the relationship between operator actions and system hazards. To illustrate our approach we present a simple case study.

Abstract
Function allocation, as a process used in the construction of dependable complex systems, is a significant aspect of the design and implementation of interactive systems. It involves a documented and rational process for deciding what aspects of the system should be controlled by which human roles in the system and how the system should be automated to support these roles effectively. As computer systems have become more advanced, and the control of systems more complex, the notion of dynamic function allocation becomes increasingly desirable where in certain situations the automation may take over or give back function to the human user. In this paper we explore a further variant of dynamic function allocation that reflects typical work activity where the dynamic scheduling of activities takes place on the time dimension. The paper discusses this approach to dynamic function allocation called dynamic function scheduling and discusses the role that timed model checking may play in helping identify dependable dynamic function scheduling solutions.