1. A method for computing, comprising: specifying a data processing system using a logical system definition, which defines logical system components having respective functionalities and a topology for interconnecting the logical system components; representing the logical system components using respective logical objects in a hierarchical object model; representing physical resources of a grid computer system using physical objects in the hierarchical object model; automatically mapping the logical objects to at least some of the physical objects, so as to allocate the physical resources to carry out the respective functionalities of the logical system components; and configuring and activating the allocated physical resources so as to cause the grid computer system to function as the data processing system, in accordance with the logical system definition.