Data Modeling Using the Entity– Relationship (ER) Model
3.1 Discuss the role of a high-level data model in the database design process.
3.2. List the various cases where use of a NULL value would be appropriate.
3.3. Define the following terms: entity, attribute, attribute value, relationship
instance, composite attribute, multivalued attribute, derived attribute, com-
plex attribute, key attribute, and value set (domain).
3.4. What is an entity type? What is an entity set? Explain the differences among
an entity, an entity type, and an entity set.
3.5. Explain the difference between an attribute and a value set.
3.6. What is a relationship type? Explain the differences among a relationship
instance, a relationship type, and a relationship set.
3.7. What is a participation role? When is it necessary to use role names in the
description of relationship types?
3.8. Describe the two alternatives for specifying structural constraints on rela-
tionship types. What are the advantages and disadvantages of each?
3.9. Under what conditions can an attribute of a binary relationship type be
migrated to become an attribute of one of the participating entity types?
3.10. When we think of relationships as attributes, what are the value sets of these
attributes? What class of data models is based on this concept?
3.11. What is meant by a recursive relationship type? Give some examples of
recursive relationship types.
3.12. When is the concept of a weak entity used in data modeling? Define the
terms owner entity type, weak entity type, identifying relationship type, and
partial key.
3.13. Can an identifying relationship of a weak entity type be of a degree greater
than two? Give examples to illustrate your answer.
3.14. Discuss the conventions for displaying an ER schema as an ER diagram.
3.15. Discuss the naming conventions used for ER schema diagrams.
