A new concept for assessing the quality of object classes in analysis models, called object-class congruency, is formally defined and discussed. Object-class congruency is based on the idea that immediate and inherited properties defined for an object class should match the common properties of the class's members. A semantic model with a formal definition is used to formalize these concepts. In addition to defining object-class congruency, two semantic-preserving transformations that convert incongruent classes into congruent classes are given. It is also explained why object-class congruency leads to better abstraction of real-world concepts and to better implementation, extension, and reuse.