Entities and Attributes

• Conceptual model: A data model, usually represented by an entity relationship diagram (ERD)
  • The client dream would be the conceptual model
• Physical model: A design for an object (a car, a house, a database, etc) which includes implementation details such as size, volume, weight, etc)
  • The physical reality will become the physical model
• All many-to-many relationships must be reduced to a set of on-t--many relationships