Subtyping Mobile Classes and Mixins

L. Bettini, V. Bono, B. Venneri

MoMi (Mobile Mixins) is a coordination language for mobile processes that communicate and exchange object-oriented code in a distributed context. MoMi's key idea is structuring mobile object-oriented code by using mixin-based inheritance. Mobile code is compiled and typed locally, and can successfully interact with code present on foreign sites only if its type is subtyping-compliant with what is expected by the receiving site. In this paper, we study a subtyping relation for MoMi that includes both width subtyping and depth subtyping, in order to achieve a significantly more flexible, yet still simple, communication pattern. Technical problems arising from the depth subtyping are solved by defining a static annotation procedure.