CS122A

Question 1

Entity

Answer 1

Real-world object, distinguishable from all other objects. Uses set of attributes.

Question 2

Entity Set

Answer 2

Collection of similar entities. E.g., all employees

1. All entities have same set of attributes.
2. Each entity has a key (unique identifier); this can be one attribute (an “atomic” key) or several attributes (“composite” key)
3. Each attribute has a domain. (similar to datatype)

Question 3

Relationship

Answer 3

Association among two or more entities.

E.g., Santa Clause works in Toy Department

Question 4

Relationship Set

Answer 4

Collection of similar relationships.

Question 5

Weak Entity

Answer 5

Can be identified uniquely only by considering, the primary key of some other(owner) entity.