Abstract: A multimedia application development system including an authoring environment and a runtime module for executing applications developed in the authoring environment is described. The system allows creation of customized objects (e.g., custom controls), by creating a user-defined class or "UDC." Typically, a UDC is created from one or more existing classes, inheriting, at least in part, behavior and functionality of those existing classes. The system provides methods where actual binding of properties and methods to an object instance of a class is deferred until runtime. With specific regard to UDC-created objects, the behaviors of parent classes are not bound to object instances at compile time. Instead, these behaviors are "late bound" by fetching them from the parent classes at runtime, on an "as needed" basis. Further, "which" particular parent classes are actually employed for this purpose at runtime can be altered, thereby providing further flexibility to the system.