Virtual Environments as Hybrid Systems

The development of virtual environments (VEs) is a non-trivial task. Many VEs are based around particular technologies and developed using ad hoc prototyping. This is undesirable if any formal evaluation of the system is to be attempted. It is also common for descriptions of VEs to be left at an informal level, if described at all. This is because VEs are dynamic environments and due to their continuous and highly visual nature, defining salient and useful aspects of them is extremely difficult. VEs are made up of a complex collection of discrete and continuous processes. Also, each individual element can be thought of as a mixed model in its own right. Thus, traditional discrete modelling techniques are not appropriate. What is proposed here is that techniques from hybrid systems research be used to mirror the hybrid nature of VEs. We demonstrate how techniques developed for modelling hybrid systems can be used to represent VE interaction. Two example interaction techniques from the VE literature are presented. Some insights gained into the nature of the VE interaction and the consideration of the hybrid model in terms of an architectural system design are discussed.