Q. What is the use of a data flow diagram? Explain the important concepts of data flow diagram.

Ans. A data flow diagram is utilized to show the functional view of an application domain. It illustrates all the important business processes and the flow of data between those processes. The major concepts used are:

(i) A process represents some type of transformation on data. It receives as input one or more inputs and after doing necessary processing generates the output. It is symbolized by a circle with the name written inside as shown

(ii) Data Flow: A data flow symbolizes data in motion and is represented by an arrow. The data flows symbolize the flow of data among stores, processes and external agents.

(iii) Data Store: A data store symbolizes the data at rest. At the time of functioning it is represented by data base or files. Graphically I am shown as in figure.

(iv) External Agent: An external mediator represents a person a system or any other software which interacts with the system by providing necessary inputs and outputs. Graphically it is symbolized by a rectangle.

(b) Depict a context diagram for a Library management system.