Designing and developing location-aware portable software applications is challenging, since most location-estimation methods i) require non-standard features either in the mobile terminal or in the network infrastructure, and ii) they are specifically designed for either indoor or outdoor. Moreover, installing and tuning systems that rely on such location methods may be quite a complex operation.

In this paper we propose a software architecture that makes a combined use of indoor and outdoor location-sensing technologies. On top of the architecture there is a generic API, aimed at supporting the development of hybrid (indoor/outdoor) applications at a high level of abstraction, independent of the location technology. The API is meant to support applications for which the exact position of a mobile terminal is not a primary requirement, but it suffices to identify the terminal position in a known set of zones (e.g., rooms indoor, or pre-defined outdoor areas). The software architecture is designed: i) to ensure compliance with emerging positioning standards and commercial devices, in order to leverage the interoperability with third-party developed services, and ii) to be based on low-cost and easily deployable and tunable indoor positioning infrastructures.

An implementation of the architecture is described, based on Bluetooth and GPS technologies, so as to outline the major implementation issues.