Data Flow Diagram

A data-flow diagram (DFD) is a graphical representation of the "flow" of data through an information system

1. TOPIC : DATA FLOW DIAGRAM PRESENTED BY: Shreya Chattopadhyay

2. DEFINITION: A data-flow diagram (DFD) is a graphical representation of the "flow" of data through an information system.

3. PURPOSE OF DFD: to provide an indication of how data are transformed as they move through the system. to depict the functions (and subfunctions) that transform the data flow. The DFD provides additional information that is used during the analysis of the information domain and serves as

4. DFD DFD shows “ flow of Data” Allows reader to determine what kinds of data will be input to and output from the system, where the data will come from and go to,where the data will be stored . FLOW CHART Flow chart shows “ flow of Control ” allows a reader to determine what operations will be performed, in what order, and under what circumstances.

5. COMPONENTS OF DFD:

6. . Entities/input-output: The sharp cornered rectangles (or simply boxes) in a DFD indicates entities. are called sources if they are external to the system and provide data to the system, and sinks if they are external to the system and receive information from the system

7. Student Doctor Teacher Manager Cashier User Customer

8. Processes/functions : The circles in a DFD indicate processes. The Process symbol represents an activity that transforms or manipulates the data (combines, reorders, converts,Prints etc.).

9. Accounting System Reservation System Patient Administration System Marketing System Grading System

10. Data Store: Two parallel lines in DFD indicate Data Store A Data Store is a repository of data . D ata can be written into the data store. This is depicted by an incoming arrow . Data can be read from a data store. This is depicted by an outgoing arrow . Two data stores cannot be connected by a data flow.

11. Order details Student’s grade Flight Database Employee’s Data Inventory

12. Data Flow: Arrow symbol in DFD indicate data flow. The Data Flow symbol represents movement of data.

13. Synchronous Operations: If two bubbles are directly connected by a data flow arrow: They are synchronous

14. A s ynchronous Operations: If two bubbles are connected via a data store: They are not synchronous

15. How to draw DFD? Context Diagram : The highest level in a data flow diagram Contains only one process, representing the entire system The process is given the number 0 All external entities, as well as Major data flows are shown

16. How to create context diagram? Identify your main system Identify the external people who interact with the system Decide what data these entities will enter into the system Determine what these entities expect as output from the system

17. Level 1 DFD. The basic module of the system are represented in this phase and how data moves through different module is shown. The level 1 DFD provides a high –level view of the system that identifies the major processes and data stores.

18. Creating Child Diagrams Each process on diagram 0 may be exploded to create a child diagram A child diagram cannot produce output or receive input that the parent process does not also produce or receive The child process is given the same number as the parent process Process 3 would explode to Diagram 3 Entities are usually not shown on the child diagrams below Diagram 0 If the parent process has data flow connecting to a data store, the child diagram may include the data store as well When a process is not exploded, it is called a primitive process

19. Example: RMS calculating software Accept input numbers from the user: Validate the numbers, Calculate the root mean square of the input numbers Display the result.

20. registers retrieves & stores DFD of Password Management Software Password Book System Customer

21. Level 1: select process retrieves pass stores Pass Save_Pass Login Form Authentication form User’s account Process Execution Exit

22. Level 2: