Class-Based and Algebraic Models of Objects
				  by
		   Gary T. Leavens and Don Pigozzi

                               Abstract

We compare different kinds of first-order models of objects and
message passing, as found in object-oriented programming languages.
We show that generic function models can easily simulate record models
for static, class-based languages.  We explore type systems for such
languages, and show that our simulation preserves typing.  Algebraic
models emerge as abstractions of the generic function model that
suppress details that are irrelevant for client code.


Keywords: object-oriented, record, generic function, type, subtype,
algebraic model, category-sorted algebra, order-sorted algebra,
semantics, type theory.

1998 CR Categories:
D.3.1 [Programming Languages] Formal Definitions and Theory --- Semantics;
D.3.3 [Programming Languages] Language Constructs --- Abstract data types;
F.3.2 [Logics and Meanings of Programs] Semantics of Programming Languages
   --- algebraic approaches to semantics, denotational sematics.