Querying Issues in Pervasive Environments

Introduction

The market of data management is lead by the major Object-Relational Database Management Systems (ORDBMS) like Oracle (http://www.microsoft.com/sqlserver/2008/en/us/). During the last twenty years, in order to better match the evolution of user and application needs, many extensions have been proposed to enhance the expressive power of SQL and the DBMS functions. In this context, querying is one of the most important functions’ (Wiederhold 1992; Domenig and Dittrich 1999) for accessing and sharing data among information sources. Several query-processing mechanisms have been proposed to efficiently and adaptively evaluate queries (Selinger 1979; Graefe and McKenna 1993; Graefe and Ward 1989; Kabra and DeWitt 1998; Haas and Hellerstein 1999; Bouganim 2000; Urhan and Franklin 2000; Avnur and Hellerstein 2000; Hellerstein et al. 2000; Raman and Hellerstein 2002). New classes of dynamic distributed environments (e.g., peer-to-peer where peers can connect or disconnect at any time) introduce new challenges for query processing. Some works add indexing structures to P2P architectures for efficiently locating interesting data and/or improving query languages expressivity (Abiteboul et al. 2004; Abdallah and Le 2005; Abdallah and Buyukkaya 2006; Labbe et al. 2004; Karnstedt 2006; Papadimos 2003). Such systems rely on a global schema and often pre-determined logical network organizations and are in general poorly adapted to query processing introduced in pervasive environments.

Pervasive computing is all about making information, data and services available everywhere and anytime thereby democratizing access to information and opening new research challenges for querying techniques. Today every activity (at home, for transportation and in industries) relies on the use of information provided by computing devices such as laptops, PDA’s and mobile phones and other devices embedded in our environment (e.g. sensors, car computers). Given the explosion of amounts of information largely distributed and produced by different means (sensors, devices, networks, analysis processes) research on query processing is still promising for providing the right information, at the right place, at the right moment.