Abstract. Aspect oriented programming brings us new design perspectives since it permits the superimpositions of multiple abstraction models on top of one another. It is a very powerful technique in separating and simplifying design concerns. In this paper, we provide detailed descriptions of our aspect oriented re-factoring of ORBacus, an industrial strength CORBA implementation. The re-factored features are the dynamic programming interface, support for portable interceptors, invocations of local objects. Their associated IDL-level re-factorization is addressed by an aspect-aware IDL compiler. In addition, we present the quantification for the changes in terms of both the structural complexity and the runtime performance. The aspect oriented re-factorization proves that AOP is capable of composing non-trivial functionality of middleware in a superimposing manner. The final ”woven” system is able to correctly provide both the fundamental functionality and the ”aspectized” fu...