4.1. Introduction

Generally speaking, an information service is a network-accessible and computer-based system to collect, process, filter, transmit, and disseminate data that represents information useful for a specific purpose or individual. Along the same lines, a location-based service (LBS) refers to the additional integration of position location information as part of the data processed by the information service. Thus an LBS provides and delivers information to its users in a highly selective manner, by taking users’ past, present, or future location and other context information into account. An LBS is often even more generally defined as any value-added service offered in a wireless environment that exploits mobile terminal location position information.

Examples comprise route-planning applications, where a repository of map information is queried to determine a possible path between two points (e.g., the Map-on-the-Move application [YJK98]); push-based targeted advertisement (e.g., an XML-based selective information dissemination service [FJL+01a]), where a user profile is maintained by the information system and notifications are delivered to users as pertinent data correlated with users’ locations and interests becomes available. Further applications are the friend finder system (see Chapter 2) and location-based games, where correlations between a number of moving users must be established; and tracking applications, where a number of moving objects must be tracked simultaneously and queries about the state of individuals or groups of objects must be processed.