Realms and states

摘要

Location awareness is an important part of context-aware mobile computing. We present the idea of logical location contexts which provides enhanced privacy and supports specialized notions of distance, and offers a paradigm that unifies location with other types of context. This is developed in the form of a framework consisting of realms, which are collections of spatial states, with realm-maps providing mappings between realms. The lowest realm relies on raw (physical) location. Multiple arbitrary realms are allowed to co-exist. Many applications do not necessarily need access to raw location. With our model, such applications access only states in specified realms of interest, thus supporting location privacy. Policies guard such access at the granularity of realms and states. Provision for specialized realm-specific and state-specific notions of distance enables spatial awareness and reasoning. The framework is presented formally. The ensuing architecture has good properties with respect toprivacy, manageability, distribution of computation and scalability.