A hybrid location model with a computable location identifier for ubiquitous computing

Abstract

Location modeling and representation are crucial technolo- gies for context-aware applications. In this paper, we present a novel location model combining the virtues of both the hierarchical and coordi- nate location models, and we introduce a computable location identifier, namely Aura Location Identifier (ALI). We then describe how the Aura space service uses this hybrid model to handle spatial queries for context- aware applications. Asimple example of such a query is a range query, e.g. "select name from printer where distance(location,‘ali://cmu/wean- hall/floor3/3100-corridor#(10,10,0)’) <10", where "location" is an at- tribute representing the location of printers. Finally, we discuss how we extended the PostgreSQL database system to provide direct support for spatial SQL queries at the database level. These extensions improve per- formance and increase flexibility for context-aware applications.