A Middleware Infrastructure for Active Spaces

P ervasive computing environments augment human thought and activity with digital information, processing, and analysis, providing an observed world that is enhanced by the behavioral context of its users. A spectrum of heterogeneous computation and communication devices aim to enhance user productivity and facilitate everyday tasks. Despite the prevalence of such devices, however, no suitable software infrastructure with which to develop applications for ubiquitous computing habitats or living spaces exists. To address this deficiency, we developed Gaia, a metaoperating system1 (detailed in the sidebar “The Gaia Operating System”) built as a distributed middleware infrastructure that coordinates software entities and heterogeneous networked devices contained in a physical space. Gaia is designed to support the development and execution of portable applications for active spaces2— programmable ubiquitous computing environments in which users interact with several devices and services simultaneously. Gaia exports services to query, access, and use existing resources and context, and provides a framework to develop user-centric, resource-aware, multidevice, context-sensitive, and mobile applications. By extending the concepts of traditional operating systems to ubiquitous computing spaces, we can simplify space management and application development. Gaia’s main contribution is not its individual services but rather the functionality it provides as the result of the interaction of these services. This interaction lets users and developers abstract ubiquitous computing environments as a single reactive and programmable entity instead of a collection of heterogeneous individual devices. In this article, we present an overview of the Gaia architecture, focusing on the complete system rather than individual services.