Behavioural subtyping and property preservation

Abstract

Inheritance is one of the key features in object-oriented design and analysis. It especially supports an incremental development by allowing to stepwise add new functionality to an existing system design. When using a subclass which is a specialisation of a certain superclass, the question arises which of the superclass' properties still hold for the subclass. We investigate this topic for three behavioural subtyping relations, which formalise the subtype - supertype relationship among classes on the basis of process algebra correctness relations. According to the degree of change allowed by the subtyping relations, safety and liveness properties of the superclass are preserved up to different extents. © 2000 International Federation for Information Processing.