I notice that member functions for many classes can be divided up into a minimal set, and derivable functions. For instance: class MyClass { void Fu() { cout << "fu"; } void Bar() { cout << "bar"; } void FuBar() { Fu(); Bar(); } } Clearly a minimal interface for representing FuBar would be: BOOST_IDL_BEGIN(IMyInterface) BOOST_IDL_FN0(Fu, void) BOOST_IDL_FN1(Bar, void) BOOST_IDL_END(IMyInterface) Using IMyInterface in our code instead of IMyInterface is more generic, and reduces coupling, but we lose the syntactic pleasantries of FuBar(). In order to achieve this effect I am currently using an extension class (or veneer if you prefer): template<typename Base_T> class MyClass_ext : public Base_T { MyClass_ext() : T() { }; template<typename T> MyClass_ext(const T& x) : T(x) { }; void FuBar() { T::Fu(); T::Bar(); } // ... assignment operators etc. } I can then write a new extended interface as follows: typedef MyClass_ext<IMyInterface> IMyInterface2; And of course I would also rewrite the original class, to avoid code redundancy: class MyClass_base { void Fu() { cout << "fu"; } void Bar() { cout << "bar"; } } typedef MyClass_ext<MyClass_base> MyClass; I don't how solid this technique is for real code. My terminology and naming convention also leaves me disatisfied. Any comments or suggestions? Christopher Diggins Object Oriented Template Library (OOTL) http://www.ootl.org