Database Systems Role of Schema Dr M Tanvir

Database Systems Role of Schema Dr. M. Tanvir Afzal

Role of Schema Give only restricted information ü Someone placing an order should not have access to the company’s financial data. ü Employees’ supervisors can ask for the information of employees records, but should not be given access to corporate inventory or sales record. ü Implemented as Schema and subschema. 2

Role of Schema and Subschema ü A schema is a description of the entire database structure that is used by the database software to maintain the database ü A subschema is a description of only that portion of the database pertinent to a particular user’s needs. 3

Role of Schema Example ü Schema of university database include student complete record, courses registered by students, student advisor information, Faculty members employment history etc. ü Registrar should not be able to see the employment history, but can see student advisor 4

Role of Schema Example continued ü The subschema for the payroll department would provide the employment history of each faculty member but would not include the linkage between students and advisers. ü Examination department should not be able to access salary information. 5

Summary Role of Schema ü Restricted Information Accessibility ü Schema ü Subschema 6