Generalized layer activation mechanism through contexts and subscribers

Context-oriented programming (COP) languages modularize context-dependent behaviors in multiple classes into layers. These languages have layer activation mechanisms so that the behaviors in layers take effect on a particular unit of computation during a particular period of time. Existing COP languages have different layer activation mechanisms, and each of them has its own advantages. However, because these mechanisms interfere with each other in terms of extent (time duration) and scope (a set of units of computations) of activation, it is not trivial to combine them into a single language. We propose a generalized layer activation mechanism based on contexts and subscribers to implement the different activation mechanisms in existing COP languages in a single COP language called ServalCJ. Contexts specify the extent of activation through temporal logic terms, and subscribers specify the scope of activation through operators provided by the language. We implement a compiler of ServalCJ, and demonstrate its expressiveness by writing a couple of application programs.