On model typing

Abstract

Where object-oriented languages deal with
objects as described by classes, model-driven development uses models, as graphs of interconnected objects,
described by metamodels. A number of new languages
have been and continue to be developed for this model-
based paradigm, both for model transformation and for
general programming using models. Many of these use
single-object approaches to typing, derived from solutions found in object-oriented systems, while others use
metamodels as model types, but without a clear notion
of polymorphism. Both of these approaches lead to brittle and overly restrictive reuse characteristics. In this
paper we propose a simple extension to object-oriented
typing to better cater for a model-oriented context, including a simple strategy for typing models as a collection of interconnected objects. We suggest extensions to
existing type system formalisms to support these concepts and their manipulation. Using a simple example
we show how this extended approach permits more flexible reuse, while preserving type safety.