Cache consistency in mobile XML databases

Abstract

Whenever an XML database is used to provide transactional access to mobile clients in multi-hop networks, standard database technologies like query processing and concurrency control have to be adapted to fundamentally different requirements, including limited bandwidth and unforeseeable lost connections. We present a query processing approach that reduces XML data exchange to the exchange of difference XML fragments wherever possible. Additionally, within our approach transactions can even use cached results of outdated queries and of neighbor clients, wherever they result in a reduction of data exchange. Furthermore, our approach supports a pipelined exchange of queries and partial answers. Finally, we present a timestamp-based approach to concurrency control that guarantees cache consistency and minimizes data exchange between the mobile clients and the XML database server. © Springer-Verlag Berlin Heidelberg 2006.