This paper discusses knowledge sharing (inheritance) mechanisms for
Object-Oriented Programming (OOP)
in the context of concurrent (distributed) languages.
We review three different schemes:
{\em inheritance}, {\it delegation} and {\it copy}.
A fourth model, called {\em recipe-query},
is presented and all are compared and criticized.
Techniques relying on the shared memory assumption are rejected.
We point out the conflict between distributing knowledge
among objects and the synchronization of concurrent objects.