Please enable JavaScript.
Coggle requires JavaScript to display documents.
DEGREES OF DATA ABSTRACTION - Coggle Diagram
DEGREES OF DATA ABSTRACTION
THE EXTERNAL MODEL
ER diagrams are used to represent the external views
External schema which is specific representation of an external view
End users’ view of the data environment
ADVANTAGES
Facilitates designer’s job by providing feedback about the
model’s adequacy
Easy to identify specific data required to support each
business unit’s operations
Creation of external models helps to ensure security constraints in the database design Simplifies application program development
THE INTERNAL MODEL
Internal schema depicts a specific representation of an internal model
Have software dependent and hardware independent
Maps the conceptual model to the DBMS
Logical independence which is changing internal model without affecting the conceptual model
THE CONCEPTUAL MODEL
Logical design, task of creating a conceptual data model
Independent of both software and hardware
Conceptual schema which is basis for identification and high-level description of the main data objects.
Most widely used conceptual model is the entity relationship (ER) model
Represents global view of the entire database by the entire organization
Provides a relatively easily understood macro level view of data environment
Advantages
Does not depend on the hardware used in the
implementation of the model
Changes in either hardware or DBMS software have no effect on the database design at the conceptual level
Does not depend on the DBMS software used to implement the model