Abstract : We propose here to show the usefulness of the addition of annotations inside the classes for a better specification of the use of the inheritance relationship in libraries of classes. The awaited added value is to improve the documentation, the reusability, the evolution capabilities and the robustness of these libraries; typically these annotations could be exploited by programming environments. We rely on existing taxonomies of inheritance to show the contribution of these annotations and we define an unified and flexible mechanism able to take into account any other taxonomy. We propose an integration of this mechanism in the Eiffel language through an extension of its clauses "inherit" and "indexing". The broad outline of the implementation based on model OFL defined in our team is also highlighted.