The present invention provides a method, data processing system and computer program product in which a plurality of software executable libraries (sub-libraries) are combined into a single software executable library. The single library comprises a plurality of register functions, each associated with a particular sub-library and each sub-library comprises one or more functions. When the library receives a request to register from a library manager it calls each of the register functions, each of which register the one or more functions of its associated sub-library with the library manager. Advantageously the library manager can subsequently interface with each sub-library as if the sub-library was a standalone library. Further a register function can be used for a library whether the library is sub-library or a standalone library, thereby reducing the effort to switch from one to the other.