Database approach provides some level of data abstraction by hiding details of data.
A data model is a collection of concepts that can be used to describe the structure of a database. By structure of a database we mean the data types, relationships, and constraints that should hold on the data.
Data models include a set of basic operations for specifying retrievals and updates on the database.
Data models also allows the database designer to specify a set of valid user defined operations on the database objects.
Categories of Data Models High-level or conceptual data models - provides concepts that are based on entities and relationship. It uses concepts such as entities, attributes and relationships. An entity represents a real-world object or concept, such as employee or a project, that is described in the database. An attribute represents some property that describes an entity, such as the empolyee's name or salary. A relationship among two or moreentities represents an interaction among the entities (e.g., relationship between an employee and a project).
Low-level or physical data models - describe the details of how data is stored in the computer (useful for computer specialists).
Representational or implementation data models - provide concepts that are between the above two extremes (may be understood by end users - record-based, object-oriented).
