When we design an object-oriented database schema, we need to
normalize object classes as we do for relations when designing a
relational database schema. However, the normalization process for an
object class cannot be the same as that of a relation, because of the
distinct characteristics of an object-oriented data model such as
complex attributes, collection data types, and the use of object
identifiers in place of relational key attributes. We need only one
kind of dependency proposed here -- the object functional dependency
-- which specifies the dependency of object attributes with respect to
the object identifier. We also propose the object normal form of an
object class, for which all determinants of object functional
dependencies are object identifiers. There is no risk of update
anomalies as long as all object classes are in the object normal form.