An Open Architecture for Developing Mobile Location-Based Applications over the Internet Rui Jos´ e, Adriano Moreira, Filipe Meneses Information Systems Department University of Minho Azur´ em, 4800-058 Guimar˜ aes, Portugal email rui,adriano,meneses @dsi.uminho.pt Geoff Coulson Distributed Multimedia Research Group Department of Computing, Lancaster University Bailrigg, Lancaster, LA1 4YR, UK geoff@comp.lancs.ac.uk Abstract The mobile Internet is enabling a broad range of new ap- plications that dynamically obtain information that is rel- evant to their current location. This type of application would greatly benefit from generic mechanisms for support- ing the association between network resources and physi- cal space, but existing systems are typically based on verti- cal approaches valid only for narrow application scenarios. This paper argues that a comprehensive solution to this is- sue should address the important challenges of heterogene- ity and openness, and proposes an approach based on the concept of location-based service, i.e. a service whose us- age is associated with physical space, as a generic abstrac- tion to support the development of location-dependent sys- tems. The paper describes a model for associating location scopes with services, an architecture to support the discov- ery of location-based services on the Internet, and a pro- totype infrastructure in which several services and applica- tions have been developed for validating the architecture. 1. Introduction With the expansion of mobile Internet services, mobile users now expect to have access to information in the places where it is more relevant and not just in front of a home PC. In particular, the increasing availability of information about the location of mobile users is prompting consider- able interest for applications that dynamically select the in- formation that is relevant for that location, raising the issue of how to support a systematic correlation between informa- tion sources and physical location. We believe that a com- prehensive solution to this issue should consider two impor- tant challenges of the mobile Internet environment. The first challenge is to abstract over the technological heterogene- 6th IEEE Symposium on Computers and Communications, 3-5 July, 2001, Ham- mamet, Tunisia ity that characterises that environment, avoiding assump- tions about the use of specific networking or positioning technologies and offering high-level abstractions capable of hiding the complexity of the system from application devel- opers. The other challenge is to create an open architecture to which new components may be added or removed, al- lowing the overall system to evolve and grow continuously without assuming a centralised control of its components. We propose to address these issues with a service-based architecture that supports location-based discovery. The de- composition of applications into independent services is a classical solution for addressing the issues of heterogene- ity and openness in distributed systems. Services provide the resources that applications need but are independent from them, and thus can be independently developed and used by multiple applications. To extend the advantages of service-based architectures to the development of location- dependent applications, we propose in this paper a model of location-based service as a generic mechanism for associat- ing network resources with location. The outline of the paper is as follows: The following section describes our model for the association between net- work services and physical location. Then, in section 3, we describe the architecture of the AROUND system, a discov- ery mechanism that allows services relevant to a specific lo- cation to be found over the Internet. This is followed, in section 4, by a case study of a prototype application that ex- ploits the location-based services framework and provides the evaluation of the system. In section 5, we analyse some existing systems relating them to our own work, and, finally, in section 6, we present our concluding remarks. 2. A Model for Location-Based Services In the context of our work, a location-based service is a process or system providing a facility to the network whose usage is directly associated with physical space.