An Experience Report on Designing and Building OGSA-DQP: A Service Based Distributed Query Processor for the Grid

OGSA-DQP is a distributed query processor exposed to users as an OGSA-compliant Grid service. This service supports the compilation and evaluation of queries that combine data obtained from multiple services on the Grid, including Grid Database Services (GDSs) provided by OGSA-DAI project. Not only does OGSA-DQP support integrated access to multiple Grid services, it is itself implemented as a collection of interacting Grid services. Thus, OGSA-DQP is an example of a Grid service with a significant amount of aggregated functionality that, in addition, illustrates how Grid service orchestrations can be used to perform reasonably complex, data-intensive parallel computations. OGSA-DQP prototype has been released and it is downloadable from www.ogsadai.org.uk/dqp/. This paper contributes an experience report on the design of OGSA-DQP, with a particular emphasis on the issues, challenges and trade-offs that the OGSA-DQP development team have had to contend with.