1. In a data processing system, a method of performing a target function by sending a message from a first computer program written in a first computer language to a target object of a target class in a second computer program written in a second computer language, the method comprising the steps of: locating a predetermined description of said target class, wherein said predetermined description includes a list of functions that are performed by said target class; locating said target function from within said target class by reading said description, searching, until said target function is located, said target object's complete class hierarchy for said target function if said target function is not located within said predetermined description; mapping said message into a format required by said second language using computer code, thereby forming a mapped message; and sending said mapped message to said target object.