1. CSCI 242 SOME Patterns in Data Models

2. LEGEND OPTIONAL ZERO OR MORE ONE MANY ONE ONE OR MORE ONE MANY

3. General association

4. TYPE Bus Bus Type

5. Aggregation/containment “Many” cardinality always on the same side. This pattern represents an instance hierarchy. Company Division Department Also: parts explosion, geographic hierarchy

6. intersection 3 entities, two 1-M relationships. “Many” cardinality on the inside. Capability Skill Employee Also: students and teachers, students and courses, parts and suppliers

7. Differing aspects of same 3 entities, two 1-M relationships. “Many” cardinality on the outside. Student Phone Address Also: employees and dependents, employees and college degrees, owners and cars

8. Subordinate or subtype “be” labels indicate that entities are two different relationships of the same concept. Full-Time Employee Part-Time Employee Employee be be be be

9. Subordinates across Subordinate descriptor always on the same side of the relationship, for an n-level inheritance hierarchy. Full-Time Employee University Person Employee be be be be

10. Reflexive association manages Employee is managed by

11. inventory Classes of inventory: 1. Items tracked individually tend to have individual identifiers tend to have differences between individuals 2 Items tracked in aggregate tend to not have identifiers only quantities are tracked Examples: 1. people, cars, houses, taxpayers, expensive art works 2 pencils, coal, gasoline, water, paint