monitoring interface; concrete implementations for MySQL [8] and MonALISA [9] are already available. The PROOF basic scheduler implementation provides the possibility to assign the worker nodes based on the load and the group priority according to the simple formula: Nworkers = N f ree CPU · f · P̄j + Nmin where N f ree CPU is the number of free CPUs on the cluster nodes, f and Nmin are, respect...