Collaborative Virtual Environments (CVEs) are shared virtual spaces designed to enhance collaboration between the -usually remote -participants. The deployment of Collaborative Virtual Environments over wide area networks increases typical network delays, potentially breaking the consistency between the replicated versions of an environment at the participants' sites. This paper presents our qualitative observations of an experiment involving two players engaged in a virtual ball game in the presence of increasing network delays. It also describes how network delay affected the participants' behaviour and produced collaboration breakdowns. We observed that, as the network delay increases, the users modify their playing strategies in an attempt to cope with the situation, presenting several types of adaptation strategy. Knowledge of the presence and effect of delays is a major factor in allowing users to adopt strategies for coping with inconsistencies. We propose that if the participants were made more aware of the behaviour of the system, e.g. the presence of delays, then they might be able to improve their performance. Consequently, we propose a number of techniques to increase the user's knowledge of infrastructural characteristics such as delay.

Delay is an unavoidable reality in collaborative environments. We propose an approach to dealing with delay in which 'decorators' are introduced into the interface. Decorators show the presence, magnitude and effects of delay so that participants can better understand its consequences and adopt their own natural coping strategies. Two experiments with different decorators show that this approach can significantly reduce errors in specific collaborative activities. We conclude that revealing delays is one way in which groupware can benefit from accepting and working with the reality of distributed systems, rather than trying to maintain the illusion of copresent interaction.

We look at differences between the experience of virtual environments and physical reality, and consider making the technical limitations which cause these differences 'visible', aiming to provide resources to enhance communication between users. Three causes of such discrepancies are considered to illustrate this idea: field-ofview; haptic feedback; and network delays. For each, we examine ways of revealing the limitations of the virtual world as resources to better understand the intricacies of system and co-user behaviour. These examples introduce a broader discussion of design issues involved in producing interfaces for day-to-day collaboration through virtual environments. Issues include: the application and activity undertaken through the virtual world; the ability to focus on the business at hand rather than the system in use; and extent of users' familiarity with application and system.

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