Foundations for dynamic object re-classification

We investigate, in the context of functional prototype-based languages, objects which might extend themselves upon receiving a message. The possibility for an object of extending its own "self", referred to by Cardelli as a self-inflicted operation, is novel in the context of typed object-based languages. We present a sound type system for this calculus which guarantees that evaluating a well-typed expression will never yield a message-not-found run-time error. The resulting calculus appears to be also a good starting point for a rigorous mathematical analysis of class-based languages. Ou