CONCURRENCY AND COMPUTATION: PRACTICE AND EXPERIENCE Concurrency Computat.: Pract. Exper. 2006; 18:621–634 Published online 8 November 2005 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/cpe.970 An adaptive parallel query processing middleware for the Grid V. F. V. Da Silva 1,2, ∗ ,† , M. L. Dutra 1,3 , F. Porto 4 , B. Schulze 1 , A. C. Barbosa 5 and J. C. de Oliveira 1 1 Computer Science Department, National Laboratory for Scientific Computation, Rio de Janeiro, Brazil 2 Informatics Department, Pontificial Catholic University, Rio de Janeiro, Brazil 3 System Engineering Department, Military Institute of Engineering, Rio de Janeiro, Brazil 4 EPFL, School of Computer and Communication Sciences, Database Laboratory, Lausanne, Switzerland 5 Computer Science Department, Federal University of Esp´ ırito Santo, Esp´ ırito Santo, Brazil SUMMARY Grid services provide an important abstract layer on top of heterogeneous components (hardware and software) that take part in a Grid environment. In this scenario, applications such as scientific visualization require access to data of non-conventional data types, such as fluid path geometry, and the evaluation of special user programs and algebraic operators, such as spatial hash-join, on these data. In order to support such applications we are developing a Configurable Data Integration Middleware System for the Grid (CoDIMS-G). CoDIMS-G provides a query execution environment adapted to the heterogeneity and variations found in a Grid environment by offering a node scheduling algorithm and an adaptive query execution strategy. The latter both adapts to performance variations in a scheduled node and deals efficiently with repetitive evaluation of a query execution plan fragment, as needed for computing a particle’s, trajectory. Copyright c  2005 John Wiley & Sons, Ltd. KEY WORDS: middleware; Grid services; database; parallel query processing 1. INTRODUCTION The development of Grid services, as proposed by the Open Grid Services Architecture (OGSA) [1], provides for the isolation of user applications in respect of the heterogeneity inherent to the ∗ Correspondence to: V. F. V. Da Silva, Computer Science Department, National Laboratory for Scientific Computation, Av. Get´ ulio Vargas 333, 25651-075, Petr´ opolis, RJ, Brazil. † E-mail: vfontes@lncc.br Contract/grant sponsor: CNPq, PCI/LNCC, CAPES, FAPERJ Contract/grant sponsor: DIP—European Union’s IST programme; contract/grant number: FP6-507483 Copyright c  2005 John Wiley & Sons, Ltd. Received 10 December 2004 Revised 22 February 2005 Accepted 1 March 2005