1. A method for controlling a manufacturing process of a plant via a MES system, which comprises the steps of: providing the MES system with a tool model catalogue, the tool model catalogue containing tool entities and tool methods on the tool entities, the tool entities contain engineering-time tool entities and run-time tool entities and the tool methods contain engineering-time tool methods and run-time tool methods; at engineering time or at run time, via a tool manager, exposing the tool model catalogue and storing information on tool model data in a database; at the engineering time, defining specific engineering-time tool entities by invoking the engineering-time tool methods; at the run time, instantiating the specific tool entities into run-time tool objects; and at the run time, controlling the manufacturing process relative to physical plant tools by invoking the run-time tool methods on the run-time tool objects.