The Use of Models of Space in Mixed-Reality Systems

In this paper we discuss the use of models of space in mixed-reality systems. By model of space we mean a distinguishable geometric or symbolic description associated with a physical space. We outline several types of model that might exist, how they are surveyed or otherwise authored, how they are represented to the users and how the underlying middleware and sensors support them. We show that systems often contain numerous models of space and that a great deal of work goes into maintaining or reifying assumptions about transformations between models. We illustrate these ideas by describing the implementation of a collaborative mixed-reality system that allows users to experience a museum in three modalities: physically co-located visitor with personal digital assistant guide, virtual reality visitor and web visitor.