1. A method for scheduling execution of a work unit in a data processing system, wherein the execution of said work unit involves the execution of a program, the method comprising: by a scheduler in a scheduling apparatus, receiving, in a request for scheduling execution of the work unit, input from a user comprising user-defined data necessary to execute the work unit, said user-defined data including data that is specific to the particular invocation of the program for the execution of the work unit, and said user-defined data including one or more among values of arguments to be passed to the program and information about resources requested for execution of the program; retrieving, by the scheduler, pre-defined data necessary to execute the work unit from a profile repository, said pre-defined data being arranged in a re-usable profile of the program to be executed, said pre-defined data including data not subject to change from invocation to invocation of the program, and said pre-defined data including one or more among information identifying the corresponding program to be executed, arguments to be passed to the program, and information about resources requested for the execution of the program; generating, by a descriptor builder in the scheduler, a work unit descriptor for the execution of the work unit by merging user-defined data and the pre-defined data, wherein said pre-defined data includes formal parameters and said user-defined data includes values to be assigned to the formal parameters, and wherein merging the user-defined data and the pre-defined data includes resolving the formal parameters in the pre-defined data by assigning thereto the respective values in the user-defined data; and scheduling the execution of the work unit based on the generated work unit descriptor.