9 Spatio-temporal Databases in the Years Ahead Manolis Koubarakis 1 , Yannis Theodoridis 2 , and Timos Sellis 3 1 Technical University of Crete, Greece 2 University of Piraeus, Greece 3 National Technical University of Athens, Greece 9.1 Introduction CHOROCHRONOS has been a fruitful and enjoyable project. It contributed many innovative ideas in the areas of ontology and data modeling, query evalu- ation and prototype systems for spatio-temporal databases. Our ideas have al- ready found uses in various application domains such as moving object databases (see Chapter 4), environmental information systems (see the Dedale application in Chapter 5), interactive multimedia applications and virtual worlds (see Chap- ter 8). CHOROCHRONOShasopenedmanyavenuesforresearchinspatio-temporal databases, but it also left us with lots of challenging research problems awaiting solution. Many of these problems have already been emphasized in the conclud- ing sections of each chapter, and there is no reason to repeat them here. 1 As an epilogue to this book, we would like to challenge the reader by discussing three important application areas and the role spatio-temporal databases can play in these. 9.2 Mobile and Wireless Computing The main concept of interest here is the concept of location (location of mo- bile clients, moving application objects and so on) and how it changes over time (a nice recent survey of this area is [10]). This application area has moti- vated a lot of spatio-temporal research recently (for research carried out outside CHOROCHRONOS see [13,14,4] and [11,6]) but there are many aspects of the problem that have not been looked at in detail. In particular, all approaches seem to adopt a centralized database view of the problem while the problem is clearly distributed [10]. Towards this direction, a recently launched European project [3], where CHOROCHRONOS researchers participate, considers both moving and stationery objects as agents that play the roles of data servers, producers and clients interchangeably. Open issues in all aspects of mobile databases arise under this consideration. 1 We are sure the seasoned database researcher can easily imagine many others! T. Sellis et al. (Eds.): Spatio-temporal Databases, LNCS 2520, pp. 345–347, 2003. c  Springer-Verlag Berlin Heidelberg 2003