data model

• data models - simple representation of complex real world data structures
• entity - anything about the stored data
• attributes - characteristics of an entity
• constraint - a restriction placed on the data
• business rules - brief description of procedures, polices or principle in an organization, must be up to date, how company view the characteristics of data, must be rendered in writing
• sources of business rules - company manager, policy maker, department manager, written document, direct interview with end users
• evolution of data models - hierarchical model, network model, relational model, entity relational model
• relational model - developed by Codd(IBM) in 1970, microcomputers run this, conceptual simple,
• entity relationship model - introduced by Chen in 1976, use graphical representation to show entity and relationship in database structures