Persistent heaps

A model for extending modular languages to support data persistence in an object-oriented paradigm is presented. The method has been applied to Modula-2 because of its powerful management of data encapsulation; comparable features can, however, be added to other object-based languages. The extension is based on the definition of a new construct which is syntactically similar to a module, supports the concepts of class and object, and implements persistent data structures. Persistence is obtained by integrating these data structures into the file system of the underlying operating system by means of an object manager. The class concept has been extended by including persistent heaps (one for each class), to allow the dynamical allocation of persistent variables, local to each object. Objects are considered second-class entities; they are used as repositories of persistent data