Composable Designs with UFA

ABSTRACT While aspe t{oriented approa hes draw their strength from improving modularity at the sour e ode level, their a eptan e for wide spread appli ation depends on a seamless embedding into the software life{ y le. When striving for an appropriate design notation for AOSD it is important to arefully balan e the abstra tion required by design with the pre ision required for implementing a given design. We hoose the Aspe tual Collaborations model [7, 5℄ as a basis, whi h allows separate development of modules omprising sets of ollaborating lasses and a posteriori integration of su h modules. We present UFA (UML for Aspe ts) as an extension of the UML, whi h maps these modules to pa kages in UML. We furthermore fo us on multiple levels of bindings between modules and their elements. UFA loses the gap between ollaboration based design and an implementation that allows unanti ipated omposition in an aspe t{oriented style. 1. WHEN DO ASPECTS ARISE? The notion of aspe ts as used in the AOP ommunity seems to be losely related to the sour e ode. It is de ned by the ross utting of on erns whi h is manifest in s attering and tangling of sour e ode. In order to de ne a notation and a method for aspe t{oriented design it is therefore important to examine whether the phenomenon of ross utting also exists in earlier phases. There are two possible reasons, why ross utting is less a problem in design, than it is in implementation: Firstly, for some aspe ts there exists a level of abstra tion at whi h they appear atomi , i.e., without internal stru ture. This is the kind of aspe ts for whi h it suÆ es to atta h a tagged value or property to ertain UML symbols in the design. Persisten e is su h a on ern, whi h may well be s attered over large parts of a model, but at a given level of abstra tion a property fpersistentg is enough to say. There would be little advantage in separating out the de -