1. DFD examples

2. Example 1
Students send in an application form containing their personal details, and their desired course. The university checks that the course is available and that the student has necessary academic qualifications. If the course is available the student is enrolled in the course, and the university confirms the enrolment by sending a confirmation letter to the student. If the course is unavailable the student is sent a rejection letter.

3. actions/doing words/verbs => Processes (P)
.     1.  Read the problem description carefully looking for:
people/organisations/things that supply information to or use information from the system => external entities (EE)
actions/doing words/verbs => Processes (P)
movement/exchange of information/data between external entities to processes, and processes to processes => data flows (DF)
store/record information/data => data stores(DS)

4. 2. Walk through the system in its logical sequence.
A student (EE) sends in an application form (DF) containing their personal details, and their desired course
The university checks (P) that the course is available.
If the course is available the student is enrolled (P) in the course, and the university confirms (P) the enrolment by sending a confirmation letter (DF) that they are registered for the course to the student.
Or if the course is unavailable the student is sent a rejection letter (DF).

5. Context diagram Highest level DFD.
Has data flows, external entities, one process (system in focus) and no data stores.
Shows the system boundary and interactions with external entities.
In this case:
External entity - Student
Process Student Administration
process application
Data Flows Application Form,
- Confirmation/Rejection Letter

6. Context diagram

7. System/Level 0 DFD External entity - Student
Processes Check available
- Enrol student
- Confirm Registration
Data Flows - Application Form
- Course Details
- Course Enrolment Details
- Student Details Confirmation/Rejection Letter
Data Stores - Courses
- Students

8. System/Level 0 DFD

9. Hoosier Burger's food ordering system
Example 2
Hoosier Burger's food ordering system
The restaurant uses an information system that takes customer orders, sends the order to the kitchen, monitors the goods sold and inventory, and generates reports for management

10. Hoosier Burger's food ordering system
The restaurant uses an information system that takes customer orders, sends the order to the kitchen, monitors the goods sold and inventory, and generates reports for management

11. Context Diagram
Context diagram shows the system boundaries, external entities that interact with the system, and major information flows between entities and the system.
NOTE: only one process symbol, and no data stores shown.

12. Level-0 DFD
Level-0 DFD shows the system’s major processes, data flows, and data stores at a high level of abstraction.
Processes are labeled 1.0, 2.0, etc. These will be decomposed into more primitive (lower-level) DFDs.

13. Example 3
Precision 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.
Draw a context diagram for the order system
Draw DFD diagram 0 for the order system

14. Context Diagram of Order System

15. Level-0 of Order System

16. Example 4
Perfect Pizza wants to install a system to record orders for pizza and chicken wings. When regular customers call Perfect Pizza on the phone, their phone number goes automatically into the Pizza system. The phone number invokes the name, address, and last order date comes automatically up on the screen. Once the order is taken, the total, including tax and delivery, is calculated. Then the order is given to the cook. A receipt is printed. Occasionally, special offer (coupons) is printed so the customer can get a discount. Drivers who make deliveries give customers a copy of the receipt and coupon (if any). Weekly totals are kept for comparison with last year’s performance.
Draw a context diagram for Perfect Pizza
Explode the context-level diagram showing all the major processes.

17. Perfect Pizza: Context Level Diagram
Management
Weekly
Report
Phone Number
Customer
Order
System
Customer
Customer Order
Customer Info
Cook
Delivery
Person
Cook Order
Delivery
Information

18. Perfect Pizza: Current Logical Level 0 Diagram
Customer
Customer Order
Phone
Number
1.0
Find
Customer
Record
2.0
Take
Customer
Order
3.0
Print
Delivery
Order
Delivery
Person
Customer
Information
Order
Information
Delivery
Information
Customer
Record
Customer
History
Discount
Info
Customer
Info
Order
Information D2
Customer History
6.0
Send
Order
to Cook D1
Customer Master
Customer
Customer
Order D3
Sales Records
Customer
Record
Sales Info
Cook
Order
7.0
Print
Weekly
Totals
5.0
Add
Customer
Record
Weekly Report
Cook
Management

19. Perfect Pizza: Current Logical Child Diagram
Customer
History D2
Customer History
3.1
Determine
Customer
Discount
Customer
Information
3.2
Record
Discount
Discount
Amount
Order
Information
3.3
Print
Delivery
Instructions
Discount
Information
Delivery
Information D3
Sales Records

20. Perfect Pizza: Current Logical Child Diagram
5.1
Record
Customer
Information
5.2
Store
Customer
Record
Customer Information
Raw
Customer
Information
Customer
Record D1
Customer Master