Pervasive and Mobile Computing 6 (2010) 218–238 Contents lists available at ScienceDirect Pervasive and Mobile Computing journal homepage: www.elsevier.com/locate/pmc Optimising context data dissemination and storage in distributed pervasive computing systems Ioanna Roussaki a,∗ , Maria Strimpakou a , Carsten Pils b , Nikos Kalatzis a , Nicolas Liampotis a a National Technical University of Athens, School of Electrical and Computer Engineering, 9 Heroon Polytechneiou Street, 15773 Zographou, Athens, Greece b Waterford Institute of Technology, Telecommunications Software & Systems Group, Waterford, Ireland article info Article history: Received 28 February 2008 Received in revised form 26 April 2009 Accepted 1 July 2009 Available online 19 July 2009 Keywords: Context Distributed Database Management System Context management & query languages Mobile physical object handling Context replication Selective context data dissemination abstract Context management systems are expected to administrate large volumes of spatial and non-spatial information in geographical disperse domains. In particular, when these systems cover wide areas such as cities, countries or even the entire planet, the design of scalable storage, retrieval and propagation mechanisms is paramount. This paper elaborates on mechanisms that address advanced requirements, including support for distributed context databases management; efficient query handling; innovative management of mobile physical objects and optimization strategies for distributed context data dissemination. These mechanisms establish a robust spatially-enhanced distributed context management framework that has already been designed and carefully implemented and thoroughly evaluated. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Network operators, sensor networks or even web resources capture valuable information such as device location and status, user profiles and movement patterns, network performance, etc., in order to provide enhanced telecommunication services to their clients. This data is considered to be vital context information [1] that can be exploited to customize services, to anticipate user intentions and to ultimately reduce human-to-machine interactions [2]. However, even though context information holds out the prospect of enhancing user experience and increasing revenues, disseminating it across distributed nodes is not straightforward. On the one hand, the various infrastructures that store and manage context data are heterogeneous, while there is no standardized interface that supports context information exchange. On the other hand, information, which cannot be retrieved when necessary, is valueless. In an open context marketplace, where a wide variety of information types is traded, context consumers are challenged by the discovery of the required context data. In this perspective, timely delivery of context information is crucial, due to the fact that most data sources provide real-time information. Thus, efficient approaches for distributed storage, retrieval and timely delivery of context data are essential for the success of context-aware computing systems. In particular, when context aware systems are not confined to a single building, but extend their functionality to cities, countries or even the entire planet, scalable and efficient data distribution mechanisms are paramount. In order to support the provision of personalized and context aware services, irrespective of the user device and the underlying network, information originating from multiple context providers is usually required [3]. These context providers do not necessarily belong to the same legal entity or administrative domain. In such a federated context management ∗ Corresponding author. Tel.: +30 210 772 24 22; fax: +30 210 772 25 30. E-mail addresses: nanario@telecom.ntua.gr (I. Roussaki), mstrim@telecom.ntua.gr (M. Strimpakou), cpils@tssg.org (C. Pils), nikosk@telecom.ntua.gr (N. Kalatzis), nliam@telecom.ntua.gr (N. Liampotis). 1574-1192/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.pmcj.2009.07.015