If the relationship is a category relation, the primary key of the child is the same as the generic. If the relationship is an identifying relationship, the primary key of the child must contain attributes inherited from the parent. Thus, when deciding whether an inherited attribute should be part of a key, an issue is whether that attribute is necessary for unique identification. It is not sufficient that it contributed to the unique identification of the parent. Foreign Keys Foreign keys are not really keys at all, but attributes inherited from the primary keys of other entities.
Foreign keys are significant because they show the relationships between entities.
Because entities are described by their attributes, if an entity is composed of attributes inherited from other entities, that entity is similar to those entities. One strength of IDEF1X lies in its roots. Having a standard and adhering to it are crucial to transferring knowledge between organizations. A weakness of nearly all methods including IDEF1X is that the modeler must be experienced in order to create good models. Modeling is not an intuitive process, and many times models will be discarded due to a poor start.