Cardinality and Modality

The fundamental parts of data modeling are attributes, data objects and relationships give the basis for understanding the information domain of a problem. Moreover additional information associated to these fundamental parts must also be understood.

We have described a group of objects, present the object relationship pairs which bind them. But a striate pair which states the object X associate to object Y does not give enough information for software engineering purposes. We have to understand how many occurrences of object X are associated to how many occurrences of object Y. This leads to a data-modeling theory which is called cardinality.