A collection of concepts that can be used to the structure of a database. By structure of a database, the data types, relationships, and constraints that should hold on data.
Categories of data model are :
1. High-level or Conceptual data model provides concepts that are close to many users perceive data.
2. Low-level or Physical data model provide concepts that describe the details of how data is stored in the computer
3. Representational or Implementation data models ,which provide concepts that may be understood by end users but that are not too far removed from the way data is organized within the computer.
4. Conceptual data models use concepts as –entities , attributes and relationship . Entity-relationship model a popular high-level conceptual data model .