Since the introduction of Smalltalk, the object-oriented paradigm has become a popular technique for the organization of data and programs. In this paradigm, objects (collections of data and programs) are organized in a class hierarchy. These classes collect similar objects and serve as a repository for methods (programs) shared by those objects. We present a new simple model of objects that allows multi-dimensional inheritance. Objects, in our model, behave like communicating processes in Hoareï¿½s CSP language, but with a different message-passing mechanism. This leads to a simple formal semantics for objects and inheritance. © 1986, ACM. All rights reserved.