Data Models

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Data Abstraction Levels






External Model

The external model is the end users’ view of the data environment. The term end users refers to people who use the application programs to manipulate the data and generate information. ER diagrams will be used to represent the external views. A specific representation of an external view is known as an external schema.



Conceptual Model

A conceptual model is graphically represented by an ERD. It integrates all external views (entities, relationships, constraints, and processes) into a single global view of the entire data in the enterprise. Also known as a conceptual schema



Internal Model

The internal model requires the designer to match the conceptual model’s characteristics and constraints to those of the selected implementation model.



Physical Model


The physical model operates at the lowest level of abstraction, describing the way data are saved on storage media such as disks or tapes.

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