Relationship memberships are further defined by cardinality and optionality.
Determines the number of entities on one side of the relationship that can be joined to a single entity on the other side.
Specifies if entities on one side must be joined to an entity on the other side.
In the following example, each Care Provider may optionally treat one or more patients. The optionality of the relationship is indicated by the o on the relationship line directly at the top of the crow's foot. The reason the relationship is optional is that we can have a new care provider that has yet to be assigned to a patient. The crow's foot indicates the one or more cardinality.
From the point of view of the patient, one or more Care Providers always treats each Patient. Notice the crow's foot without the o on the line next to the Care Provider. This relationship membership is mandatory (at least for this business), in that a Patient must be assigned to some Care Provider. This is known as a many-to-many relationship.
Note: Other objects within CA Gen support optionality and cardinality. This section deals only with their function in regard to relationships.
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