Michael D. Harrison

Model Checking Interactor Specifications

Recent accounts of accidents draw attention to “automation surprises” that arise in safety critical systems. An automation surprise can occur when a system behaves differently from the expectations of the operator. Interface mode changes are one class of such surprises that have significant impact on the safety of a dynamic interactive system. They may take place implicitly as a result of other system action. Formal specifications of interactive systems provide an opportunity to analyse problems that arise in such systems. In this paper we consider the role that an interactor based specification has as a partial model of an interactive system so that mode consequences can be checked early in the design process. We show how interactor specifications can be translated into the SMV model checker input language and how we can use such specifications in conjunction with the model checker to analyse potential for mode confusion in a realistic case. Our final aim is to develop a general purpose methodology for the automated analysis of interactive systems. This verification process can be useful in raising questions that have to be addressed in a broader context of analysis.

Allocation of function: scenarios, context and the economics of effort

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 operators 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 operators 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.

Formally Verifying Interactive Systems: A Review

Although some progress has been made in the development of principles to guide the designers of interactive systems, ultimately the only proven method of checking how usable a particular system is must be based on experiment. However, it is also the case that changes that occur at this late stage are very expensive. The need for early design checking increases as software becomes more complex and is designed to serve volume international markets and also as interactions between operators and automation in safety-critical environments becomes more complex. This paper reviews progress in the area of formal verification of interactive systems and proposes a short agenda for further work.

Systematic Analysis of Control Panel Interfaces Using Formal Tools

The paper explores the role that formal modeling may play in aiding the visualization and implementation of usability requirements of a control panel. We propose that this form of analysis should become a systematic and routine aspect of the development of such interfaces. We use a notation for describing the interface that is convenient to use by software engineers, and describe a set of tools designed to make the process systematic and exhaustive.

A toolset supported approach for designing and testing virtual environment interaction techniques

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.

A Review of Formalisms for Describing Interactive Behaviour

This paper reviews the state of research linking formal specification and interactive systems. An appreciation of Human Computer Interaction has become increasingly important within Software Engineering. As systems have become more complex there is an increasing awareness of the consequences of human error. As a result the formal specification of interactive behaviour has become a pressing topic of research. The notations considered here describe both the capabilities and resources of users in relation to a specific system and those aspects of an interactive system that must be analysed from a user perspective before implementation. The review concludes by surveying ongoing work which attempts to bridge the gap between disciplinary standpoints.

Unifying views of interactors

Interactors are components in the description of an interactive system that encapsulate a state, the events that manipulate the state, and the means by which the state is made perceivable to users of the system (the presentation). This paper concerns the relationship between the models of interactors that are being developed, at York and Pisa, in the context of Esprit Basic Research Action 7040 (Amodeus-2). The models differ in their expression of the three components of an interactor, and after relating the models to the informal notion of interactor we describe the context in which the view of interaction afforded by each model is appropriate.

Interaction engineering using the IVY tool

This paper is concerned with support for the process of usability engineering. The aim is to use formal techniques to provide a systematic approach that is more traceable, and because it is systematic, repeatable. As a result of this systematic process some of the more subjective aspects of the analysis can be removed. The technique explores exhaustively those features of a specific design that fail to satisfy a set of properties. It also analyzes those aspects of the design where it is possible to quantify the cost of use. The method is illustrated using the example of a medical device. While many aspects of the approach and its tool support have already been discussed elsewhere, this paper builds on and contrasts an analysis of the same device provided by a third party and in so doing enhances the IVY tool.

Reviewing Designs for a Synchronous-Asynchronous Group Editing Environment

The roots of computer supported cooperative work (CSCW) are in the observation that a great deal of our daily activity involves some form of collaboration (Olson 1989). Much early research in CSCW considered ways of supporting a general concept, that of cooperative work. More recently CSCW research has begun to focus on specific applications. Computer support for collaborative writing, particularly in the form of a shared editing environment, emphasizes a more task-focused approach to CSCW applications.

Using Interaction Framework to guide the design of interactive systems

Understanding the properties of interactions is essential to the design of effective interactive systems involving two or more agents, and to the evaluation of existing systems. This understanding can inform the design of multi-agent systems by helping the designer identify properties that a system should conform to. In addition, a focus on the properties of interactions can lead to a better understanding of the space of possibilities, by recognizing features of multi-agent systems which are often simply incidental outcomes of design, not explicitly considered in the design specification. We present an Interaction Framework, in which abstract interactional requirements and properties can be expressed in a way which is not biased towards the perspective of any one agent to the interaction. These can be used to derive requirements on the design of computer systems, to highlight those aspects of users which influence the properties of the interaction, and hence to guide the design of the interactive system.