Dynamically configuring an application program at run-time via one or more extension objects. The invention software implements a framework with one or more extension objects providing functionality to an application program and an application manager for integrating the functionality with the application program during execution of the application program. The framework of the invention also formulates and routes application messages between extensible objects of one application program and extensible objects of other application programs implementing a similar, dynamically extensible application program framework. On receipt of messages or notifications, the framework of the receiving application program facilitates the discovery of the intended recipient extension object and routes the message accordingly.