Controlling Consistency within Collaborative Virtual Environments

Collaborative Virtual Environments (CVE) are a form of telecommunication technology that bring together co-located or remote, participants within a spatial social and information context. Collaboration occurs between people and often around shared objects. Fruitful cooperation is helped by natural and intuitive ways of communicating and sharing, for which responsiveness and consistency are leading factors. Many CVEs maximise local responsiveness through a process of localisation and database replication, increasing responsiveness at the cost of lowering consistency. This is acceptable provided the application does not require the shared manipulation of objects. Those that do, require consistency control that provide sufficient synchronisation, ordering and update control, whilst maximising concurrence and thus the responsiveness of the system. This paper describes the major issues and principles of consistency control and demonstrates how we have applied many of these principles in three CVEs.