A modular object initialization protocol

Object-oriented class-based languages provide mechanisms for the initialization of newly-created objects. These mechanisms specify how an object is initialized and what information is needed to do so. The initialization protocol is usually implemented as a list of constructors. It is often the case that the initialization protocol concerns some orthogonal properties of objects. Unfortunately, if those properties have more than one option of initialization, the total number of constructors becomes exponential in the number of properties. Moreover, extending an existing class, even with only one feature concerning an object property, often requires defining one constructor for each of the parent constructors. As a further consequence of the fact, the subclass constructors must reference explicitly its superclass constructors. In this paper, we propose an alternative approach to the classical object initialization protocol. In our approach, instead of defining a list of constructors, it is possible to split blocks of definitions into smaller and composable pieces, in order to obtain reduction in the size of the code, better reusability, more expressiveness, and easier maintenance. To describe this idea, we present a modification of Java called JavaMIP.