This chapter compares three object methodologies: entity-relationship (ER) modeling, S. Shlaer and S. J. Mellor’s Information Modeling, and R. Rumbaugh’s Object Modeling Technique (OMT). The OMT is used to develop software objects that have both a data structure and behavior. In OMT, however, there can be a qualified association, which enhances the identification of an association by attaching an identifying attribute to a dependent class. OMT notation can more thoroughly define an attribute because it uses data types, default values, and class attributes. OMT uses the term multiplicity to represent both cardinality and participation as defined by the ER model. A qualifier and ordering constraint are used in OMT to further clarify an association. A qualifier can be used to reduce the multiplicity of an association. An ordering constraint which is shown at the many side of an association shows that the object requires a specific order to be a valid relationship.