SOFTWARE—PRACTICE AND EXPERIENCE Softw. Pract. Exper. 2002; 32:1035–1049 (DOI: 10.1002/spe.468) PLEIADES: An Internet-based parallel/distributed system D. Koulopoulos, K. Papoutsis *,† , G. Goulas and E. Housos Computer Systems Laboratory, Department of Electrical and Computer Engineering, University of Patras, GR-26500 Rio, Patras, Greece SUMMARY The use of LAN-based clusters of computers for computational purposes has been in use for several years with significant success and acceptability. The introduction of the Internet infrastructure as the interconnection medium of the cluster allows for additional flexibility and transparency of such systems. PLEIADES is an Internet-based parallel/distributed system whose purpose is to allow users to use distant computational resources in order to form virtual clusters. In addition, PLEIADES can be used as a computational infrastructure service provider for applications in need of computational resources. PLEIADES uses a tiered architecture with particular emphasis on the existence of a middle tier, whose task is to assist in the communication between the interface and the resource management tiers. The existence of the middle tier allows for the creation of an open system that is able to easily integrate with new resource management platforms and tools. Since the use of a mature resource management system for parallel/distributed computing was a prerequisite of the PLEIADES architecture, the Condor resource management environment was used. The design and implementation characteristics of PLEIADES together with some experimental uses of the system are also presented. Copyright  2002 John Wiley & Sons, Ltd. KEY WORDS: parallel/distributed computing; service provider; Condor; XML INTRODUCTION The existence of a high-bandwidth interconnection network among most university and research centers has given new potential to applications like Internet-based parallel/distributed processing and remote application access and submission, that were traditionally perceived as LAN-based applications. In particular, the possibility to consider resources, which were, from a communication point of view, difficult to reach and utilize as part of the local computation environment, has given a new rationale for the creation of Internet-based computer clusters. These developments have also been * Correspondence to: K. Papoutsis, Computer Systems Laboratory, Department of Electrical and Computer Engineering, University of Patras, GR-26500 Rio, Patras, Greece. † E-mail: kpap@ee.upatras.gr Contract/grant sponsor: Greek General Secretariat of Research and Technology, Program PENED 99 Copyright  2002 John Wiley & Sons, Ltd. Received 20 July 2001 Revised 2 January 2002 Accepted 14 March 2002