Corine Cauvet Farida Semmak Abstraction Forms in Object-Oriented Conceptual Modeling: Localization, Aggregation and Generalization Extensions 149-171 conf/caise/94 CAiSE 1994 db/conf/caise/caise94.html#CauvetS94 http://dx.doi.org/10.1007/3-540-58113-8_168