ABSTRACT
Grid systems include an aggregation of computational resources, storage resources, network resources and scientific instruments. These resources construct the so-called grid fabric of the grid [106]. Computational resources may be supercomputers, servers, dedicated computers, PCs or clusters existing in several geographically distributed organizations. Scientific instruments such as telescopes and sensor networks provide real-time data that can be transmitted directly to computational sites or that can be stored in a database. These instruments are most of the time distributed, heterogeneous and hybrid. To effectively use these resources, we need some middleware for accessing grid resources, facilitating usage of these resources, and protecting the interest of resource providers.
