In this section discussed about data flow diagram, Entity relationship diagram. these things are represented as diagrams with proper notation.

Data Flow Diagram

The data flow diagram is one of the most improvement tools used by the system analyst DeMacro (1978) Nad Gand Sarson (1979) popularized the use if the data flow diagram as modeling tools through their structured system analysis methodologies.

There are four kinds of system components


Process show what system does. Each process has one or more data inputs and produce one or more data output, Circles in a data flow diagram represent process. Each process has unique name and number. This name and number appear inside the circle that represents the processes in a data flow diagram.

This process is represented as circle

 Data Stores

File or data store is depositary of data. They contain data that is retained in the system. Processes can enter the data into a data store or retrieve data from the data store. Each data store is represented by thin line in the data flow diagram and each data store has a unique name.

The data store is represented in form of a line


Data Flows

Dataflow model the passage of data in the system and are represented lines joining system components. An arrow indicates the direction of the flow and the line labeled by the name of the data flow.