Mostly modular composition of crosscutting structures by contextual predicate dispatch (extended version)

The modularity of aspect-oriented programming (AOP) has been a controversial issue. To investigate this issue compared with object-oriented programming (OOP), we propose a simple language providing AOP mechanisms, which are enhanced traditional OOP mechanisms. We also present its formal system and then show that programs in this language can be only mostly modularly (i.e. separately) typechecked and compiled. We mention a source of this unmodularity and discuss whether or not it is appropriate to claim that AOP breaks modularity compared with OOP.

Recent work has introduced class sharing as a mechanism for adapting a family of related classes with new functionality. This paper introduces homogeneous family sharing, implemented in the J&h language, in which the sharing mechanism is lifted from class-level sharing to true family-level sharing. Compared to the original (heterogeneous) class sharing mechanism, homogeneous family sharing provides useful new functionality and substantially reduces the annotation burden on programmers by eliminating the need for masked types and sharing declarations. This is achieved through a new mechanism, shadow classes, which permit homogeneous sharing of all related classes in shared families. The new sharing mechanism has a straightforward semantics, which is formalized in the J&h calculus. The soundness of the J&h type system is proved. The J&h language is implemented as an extension to the J & language. To demonstrate the effectiveness of family sharing, the Polyglot compiler framework is ported to J&h.