Overwhelmed by the need to specify constraints, most of the OO-community does not yet take into account the most important kind of business rules: inter-related derivation rules representing supporting knowledge (e.g. policy or regulation) for the operation of some business process, that need reasoning to be applied (= rule-based paradigm). OOA/D needs a paradigm shift to enable more realistic modeling of business, including these knowledge aspects. This can be achieved by integration of advanced OO methods, like Catalysis and SDF-OO, with CommonKADS, the de facto standard for knowledge modeling. The only development tool that supports complete integration of the rule-based paradigm with the OO-paradigm today, is Platinum’s Aion. So this tool is ready for a structure preserving implementation of the next generation of OO models, that will take knowledge aspects into account.