3 tier client server architecture
•Common web application.
•Middle layers is called web server or application server.
Acts like a connections for sending data between the database server and the client.
•Security – encrypt data at the server before transmission and decrypt data at the client.
•Data Model: A set of concepts to describe the structure of a database, and certain constraints that the database should obey.
•Data Model Operations: Operations for specifying database retrievals and updates by referring to the concepts of the data model. Operations on the data model may include basic operations and user-defined operations
Categories of data models
•Conceptual (high-level, semantic) data models: Provide concepts that are close to the way many users perceive data. (Also called entity-based or object-based data models.)
•Physical (low-level, internal) data models: Provide concepts that describe details of how data is stored in the computer.
•Implementation (representational) data models: Provide concepts that fall between the above two, balancing user views with some computer storage details.Data Models
Most Recent Trend. Started with Informix Universal Server. Exemplified in the latest versions of Oracle-10i, DB2, and SQL Server etc. systems