Thursday, 22 September 2011

Client-Server Database Application and Entity Relationship Model

Client-Server Database Application


Earlier multi-user architectures used mainframe computer to process the database. The mainframe computer provides all the functions to the connected user directly. The mainframe contains the DBMS software, application programs, and user-interfaces. The users connected to the mainframe through their terminals. The remote users were connected to mainframe in a communication network.
In the mid 1980s, most users began to share data through local area network (LAN). The microcomputers were linked in a LAN so that data and resources such as printers, storage devices etc could be shared. The LAN enabled the users to send data to one another through computers, The first application of LAN enabled the users to share the resources such as printers, storage devices (e.g., large capacity disk) and to communication via electronic mail. The end-users also wanted to share their database, which led to the development of multi-user database application on local area networks. After this, the Client-Server architecture was introduced to share data on the computer network.

Entity-Relationship Model
The relational model also has limited modeling, capabilities. In 1976, Peter Chen presented the Entity-Relationship model for database design. The E-R data model is a detailed. logical representation of the data for organization. The E-R model is expressed in terms of entities, relationships between entities and the attributes (or properties) of both the entities and their relationships. The E-R model is normally expressed as an E-R diagram, which is a graphical representation of an E-R  model
Entity-Relationship Model

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