week 2 : Entity Relationship Modeling

Question 1

what is an ER model

Answer 1

• detailed and logical representation of the data for an organization or for a business area

Question 2

how are ER models expressed?

Answer 2

• in terms of entities in the business environment
• relationships or associations among those entities
• attributes or properties of both the entities and their relationships

Question 3

why ER modeling?

Answer 3

• precise understanding of the nature of the data and how it is used by the enterprise
• model for communication (non-technical and free of ambiguities)

Question 4

ER modeling notations

Answer 4

• there are no standard representation of ER diagrams
• complexity of ER modeling :
  1) understanding of the business
  2) recognition of the entities that play a role in that business
  3) relevant attributes that describe the entities
  4) relationships that connect the entities

Question 5

entity type

Answer 5

• group of objects with the same properties, identified by enterprise as having an independent existence
• entity occurrence : uniquely identifiable object of an entity type