Resume here next time to review and show the model

External Model

  • End user’s view of the data environment
  • E/R diagrams are used to represent the external views
  • Here we create the External schema with some specifics

Draw on board Conceptual Model

Conceptual Model

  • Represents a global view of the entire database by the entire organization
  • Here we create the Conceptual schema as the basis for the identification and high-level description of the main data objects
  • Has a macro-level view of data environment
  • Is software and hardware independent
  • Logical design: Task of creating a conceptual data model

Draw on board Internal Model

Internal Model

  • Representing database as seen by the DBMS mapping conceptual model to the DBMS
  • Here we create the Internal schema which is the specific representation of an internal model
  • Uses the database constructs supported by the chosen database
  • Is software dependent and hardware independent
  • Logical independence: Changing internal model without affecting the conceptual model

Draw on board Physical Model

Physical model

  • Operates at lowest level of abstraction
  • Describes the way data are saved on storage media such as disks or tapes
  • Requires the definition of physical storage and data access methods
  • Relational model aimed at logical level
  • Does not require physical-level details
  • Physical independence: Changes in physical model do not affect internal model

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