The coalgebraic perspective on objects and classes in object-oriented programming is elaborated: objects consist of a (unique) identifier, a local state, and a collection of methods described as a coalgebra; classes are coalgebraic (behavioural) specifications of objects. The creation of a "new" object of a class is described in terms of the terminal coalgebra satisfying the specification. We present a notion of "totally specified" class, which leads to particularly simple terminal coalgebras. We further describe local and global operational semantics for objects. Associated with the local operational semantics is a notion of bisimulation (for objects belonging to the same class), expressing observational indistinguishability. AMS Subject Classification (1991): 18C10, 03G30 CR Subject Classification (1991): D.1.5, D.2.1, E.1, F.1.1, F.3.0 Keywords & Phrases: object, class, (terminal) coalgebra, coalgebraic specification, bisimulation 1. Introduction Within the object-oriente...

classes and Imitation (aka Interfaces and Realization or Implementation) 19 12 SLAM predened classes and hierarchy 20 13 Run time declarative debugging 22 14 Development environment support 23 15 Revisiting things 23 References 24 A Some SLAM examples 25 DRAFT B Ideas 25 B.1 Clases mas abstractas (AHN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 C Major characteristics (AHN) (the rst version) 27 C.1 Module and type system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 C.2 Error treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 C.3 Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 C.4 Environment and libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 DRAFT 1 Introduction 3 1 Introduction SLAM is an object oriented formal specication language. The language is the soul of a system that integrates all the stages in the programmi...