View of Data in DBMS
The major goal of a database system is to provide user the abstract view of data, that is, the system hides certain details of how the data is stored and accessed. 1. Data Abstraction: To simply the user interaction with the system, the developers hide the system complexity through several levels of abstraction: Physical level: This is the lowest level of abstraction. It hides from the user how the data are actually stored. It also describes the complex low level data structure in detail. Logical level: This is next higher level of abstraction. It describes what data are stored in database and what relationship exists among these data. It thus describes the database in simple structure. View level: This is the highest level of abstraction. The system may provide many views of the same database. The view level describes only a part of the entire database to simplify the interaction with the user. Figure 1: The three levels of data abstraction For example, in P