Evaluating location dependent queries using ISLANDs

Abstract

The recent emergence of handheld devices and wireless networks implies an exponential increase in the numbers of terminals users. Given this increase, today's service providers have to propose new applications adapted to mobile environments. In this article, we focus on distributed proximity M-services, in which several handheld devices, situated in close physical proximity to one another, can communicate and exchange data. Proximity M-services exploit a combination of mobile devices and heterogeneous mobile and/or fixed networks, and require a high degree of flexibility in order to permit easy and rapid application development. Because these applications are based on. the Hybrid Peer-To-Peer (P2P) software architecture, such problems as scalability, deployment, security, reliability and information retrieval in M-services, can be more easily resolved than in other architectures. Within the framework of this software architecture, we focus on the localization problematic. Existing localization solutions are not well adapted to the mobility, dynamicity and heterogeneity of the Proximity M-service environment. Our solution to this lack of adaptation is ISLANDS, a service designed to aid the user in identifying and locating information and/or services within a communication area. ISLANDS is a decentralized service derived from the directory service model and adapted to the management of numerous distributed resources. In addition, ISLANDS provides querying facilities and a query evaluation model adapted to distributed directory management. Since most ISLANDS users are mobile, location dependent queries are also supported, thus enabling users to track down the closest theater or, more importantly in an emergency, the closest general practitioner's office. Doing so obviously requires pinpointing the location of the query issuer, and one of the original aspects of our approach is the adaptability of the localization process : given that few handheld devices today are equipped with geo-localization features, ISLANDS is able to return approximate solutions by estimating the position of the client terminal, although ISLANDS can also use GPS-like techniques if available. © Springer-Verlag 2004.