PolyTOIL is a new statically-typed polymorphic object-oriented programming language that is provably type-safe. By separating the de nitions of subtyping and inheritance, providing a name for the type of self, and carefully de ning the type-checking rules, we have obtained a language that is very expressive while supporting modular type-checking of classes. The matching relation on types, which is related to F-bounded quanti cation, is used both in stating type-checking rules and expressing the bounds on type parameters for polymorphism. The design of PolyTOIL is based on a careful formal de nition of type-checking rules and semantics.

In this paper we present an extension to basic type theory to allow a uniform construction of abstract data types (ADTs) having many of the properties of objects, including abstraction, subtyping, and inheritance. The extension relies on allowing type dependencies for function types to range over a well-founded domain. Using the propositions--as--types correspondence, abstract data types can be identified with logical theories, and proofs of the theories are the objects that inhabit the corresponding ADT. 1 Introduction In the past decade, there has been considerable progress in developing formal account of a theory of objects. One property of object oriented languages that make them popular is that they attack the problem of scale: all object oriented languages provide mechanisms for providing software modularity and reuse. In addition, the mechanisms are intuitive enough to be followed easily by novice programmers. During the same decade, the body of formal mathematics has be...

We present an imperative calculus for a class-based language. By introducing classes as the basic object-oriented construct in a -calculus with records and references, we obtain a system with an intuitive operational semantics. Objects are instantiated from classes and represented by records. The type system for objects uses only functional, record, and reference types, and there is a clean separation between subtyping and inheritance. We demonstrate that the calculus is sound and suciently expressive to model advanced language features such as inheritance with method rede nition, multi-level encapsulation, and modular object construction.

In this paper we present the type system of the TIGUKAT database programming language. It is a highly parametric object-oriented type system that combines multiple dispatch with reflexivity, separation of interface and implementation, precise behavior typing, and union and intersection types. We demonstrate the inner workings of the type system by considering a concrete example of type specification in TIGUKAT. We also review type systems of several existing programming languages and conclude that the proposed type system has a unique combination of features particularly suited for object-oriented database programming. This is an expanded version of the extended abstract submitted to DBPL 97. 1 INTRODUCTION 1 1 Introduction In the past two decades, several new database application areas have emerged. These new areas include office automation systems, geographical information systems, CASE tools, medical systems, and CAD/CAM systems. These complicated applications demand new, more ...

We describe an object calculus with selftype and binary methods. The main feature of this calculus is that it allows both extension of objects and arbitrary hiding of methods. This is made possible by the use of views. A view is a name that specifies an interface to an object. A set of views is attached to each object, and a method can be invoked either directly or via a view of the object. We prove subject reduction for the calculus. We also present a class-based extension to this calculus and a typed translation of this extension to the core calculus.

This paper is devoted to a comprehensive study of polymorphic subtypes with products.