Lecture 5

Question 1

What are the type of relations in an ER model?

Answer 1

• Entity and enitity sets
• Attributes
• Relationships

Question 2

What is an ER-diagram?

Answer 2

A diagram with nodes and connecting verices

Question 3

What do the nodes represent in an ER diagram?

Answer 3

Entity sets: rectangles
Attributes: ovals
Relationships: diamonds

Question 4

What kind of edges are in an ER-diagram?

Answer 4

Normal edges: Between ES and attribute, or ES and relationship if relationship is ‘many-many’

Arrow: from relationship to ES fro ‘many-one’ and ‘one-one’ case

Question 5

What does ES stand for?

Answer 5

Entity sets