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Mixin-based inheritance is an inheritance

Abstract. Current i n terface descriptions are poor in describing components, because they only provide an external view on a component and they do not lay d o wn how components interact with each other. Suggestions to improve component i n terface descriptions at last year's workshop are reconsidered and reuse contracts are put forward as a solution that goes one step further.

Agora is a framework for exploring object-oriented languages. In this paper we will discuss a particular prototype-based instance of Agora that features a general mixin-based approach to (multiple) inheritance. One of the major innovations of Agora is that many important features of object-orientation including inheritance, slot access, reification, cloning and inline objects are introduced by means of message passing rather than by ordinary programming structures.The syntax and semantics of Agora is explained and illustrated with examples. Furthermore, an FTP-site is given where a Smalltalk implementation of Agora can be found.

Since an object-oriented framework is an evolving artifact, ensuring consistency between its documentation and its implementation is difficult. This paper reports on the use of open hypermedia to keep framework documentation up-to-date. In particular, we demonstrate how one can feed framework contracts into computational hypermedia links to ensure the consistency between the source code and the framework cookbook.