Towards a theory of packages

Abstract

A model for packages is introduced, along with operations for their manipulation. The model is based on the unifying principle that programs should be represented by trees, and packages by substitutions on trees. Operations are defined on packages, that allow the construction of any package from a collection of basic packages. A programming environment, based on this model, would allow manipulations and operations that are not possible in current languages. Information hiding and encapsulation are automatically supported by the model. A typing mechanism is presented, which allows polymorphic types. The typing does not affect the typeless aspect of the model.