Transactions in GIS, 2006, 10(1): 5–23 © 2006 The Authors Journal compilation © 2006 Blackwell Publishing Ltd Research Article Mobile Space-Time Envelopes for Location-Based Services Allan Brimicombe Centre for Geo-Information Studies University of East London Yang Li Centre for Geo-Information Studies University of East London Abstract The convergence and miniaturisation of a range of information and communication technologies, together with increasing bandwidth availability and near ubiquity of mobile phones, are giving rise to a technological environment in which location-based services (LBS) can realistically develop. In this paper we review the nature of location- based services and the implications for data and spatial queries. In doing so, we put forward a research agenda that arises for geographical information science and engineering. Central to LBS are problems of response time and the information utility of responses to queries and any pushed alerts, where information utility refers to content, timeliness and geographical footprint. Within a publish/subscribe model of LBS provision, we propose mobile space-time envelopes as a novel approach to event brokerage. These envelopes simultaneously provide ‘soft clip’ pruning of candidate data sets in anticipation of queries, and provide the trigger that subscribers are pertinently in-range for alerts. We present the geometrical, algebraic and algorithmic concepts of mobile space-time envelopes and provide an example of these mobile envelopes in action. We conclude with a discussion of how this initial implementation could be further developed to incorporate added spatio-temporal intelligence. 1 Introduction In recent years, the convergence and miniaturisation of technologies has lead to a signif- icant blurring of the traditional means of access to electronically-stored, electronically- delivered information. Thus, for example: • formerly static devices, serviced by fixed-line networks only, have been un-tethered by wireless networks; Address for correspondence: Allan Brimicombe, Centre for Geo-Information Studies, University of East London, University Way, London E16 2RD, UK. E-mail: a.j.brimicombe@uel.ac.uk