1. DATA FLOW DIAGRAM

2. Sequence of logical and physical system view
Study current system
Derive logical equivalent
Determine system requirements
Design new logical system
Design new physical system

3. Physical System
Department
Person
File
Step number
Procedure

4. Logical components Data flows Processes Data stores Origins
Destinations

5. Physical Data Flow Diagram
An implementation dependent view of current system showing what tasks are carried out and how they performed.
It includes Name of people ,name of departments ,locations ,master and transaction files

6. Logical Data Flow Diagram
An implementation independent view of system focusing on the flow of data between processes without regard for the specific device.

7. Creating Data Flow Diagrams
General steps:
1. Create a preliminary Context Diagram
2. Identify Use Cases, i.e. the ways in which users most commonly use the system
Create DFD fragments for each use case
Validate DFDs with users.

9. Context Diagram One process, numbered 0.
Top-level view of IS
A data flow diagram (DFD) of the scope of an organizational system that shows the system boundaries, external entities that interact with the system and the major information flows between the entities and the system
One process, numbered 0.
Sources and sinks (external entities) as squares
Main data flows depicted

10. Context Diagram of Order System

11. Level-1 DFD
Shows the system’s major processes, data flows, and data stores at a high level of abstraction
When the Context Diagram is expanded into DFD level-1, all the connections that flow into and out of process 0 needs to be retained.

12. Level-1 DFD of Order System

13. Figure 1 Context diagram of Food ordering system

14. Figure 2 Level-1 DFD of food ordering system

15. Figure 3 Level-2 DFD of food ordering system

16. Strategies for Developing DFDs
Top-down strategy
Create the high-level diagrams (Context Diagram), then low-level diagrams (Level-0 diagram), and so on
Bottom-up strategy
Create the low-level diagrams, then higher-level diagrams

17. Exercise:
Gitajanli Tools sells a line of high-quality woodworking tools. When customers place orders on the company’s Web site, the system checks to see if the items are in stock, issues a status message to the customer, and generates a shipping order to the warehouse, which fills the order. When the order is shipped, the customer is billed. The system also produces various reports, such as inventory reports for Accounting.

18. Identify Entities,Process,Data Stores & Data Flow
Customer
Warehouse
Accounting
Processes
1.0 Check Status
2.0 Issue Status Messages
3.0 Generate Shipping Order
4.0 Manage Accounts Receivable
5.0 Produce Reports
Data Stores
D1 Pending Orders
D2 Accounts Receivable
Data Flows
Order
In-Stock Request
Order Data
Status Data
Status Message
Shipping Order
Invoice
Shipping Confirmation
Payment
Accounting Data
Accounts Receivable Data
Inventory Reports
1.0
2.0
3.0
4.0
5.0

19. Context Diagram of Order System

20. Level-0 of Order System