“…Scientific parallel database systems, such as Volcano [38], MIDAS [39], XPRS [40], Gamma [23], Monet [32], Bubba [15], Cocoon [41], Goblin [42] and Prima [18], provide a declarative interface for querying data, which allows users to be insulated from details on the machine architecture and physical characteristics of data. In those systems, query optimization and parallelization are automatic, having as a result an operator tree that represents a query's evaluation plan.…”