Data Model

• A data model is a collection of conceptual tools for describing data, data relationships, data semantics, and consistency constraints.
• There are two data models : the entity–relationship model and the relational model.
• The entity–relationship (E-R) model is a high-level data model. It is based on a perception of a real world that consists of a collection of basic objects, called entities, and of relationships among these objects.
• The relational model is a lower-level model. It uses a collection of tables to represent both data and the relationships among those data. Its conceptual simplicity has led to its widespread adoption; today a vast majority of database products are based on the relational model. Designers often formulate database schema design by first modeling data at a high level, using the E-R model, and then translating it into the the relational model.