1. An Introduction to Level 0 and Level 1 DFD’s.
Data Flow Diagrams
An Introduction to Level 0 and Level 1 DFD’s.

2. What is a DFD?
A data flow diagram is a…

3. What is Level 0 DFD?
Level 0 shows the main system and what data or objects are passed to/from external entities.
If the system is a whole company, external entities are people who do not work in the company being modelled or other companies.
If the system is a department, external entities are other departments or people who do not work in the dept being modelled.

4. Worked Example

5. Your Turn

6. How to create a Level 0 dfd.
Make the following headings in your jotter:
System Name;
External Entities;
Data Flow; &
Physical Flow.
Go through the passage and write down any of the above under the headings.

7. Worked Example - System Name External Entities Data Flow Physical Flow
Now you do Your turn -

8. Your Turn - System Name External Entities Data Flow Physical Flow
Now you do Your turn -

9. How to create a Level 0 dfd.
The system name goes in a hard box in the middle of the page.
<System Name>

10. How to create a Level 0 dfd.
Each external entity goes in an oval box either to: the left and right if there are two; left, right and bottom if there are three; or left right bottom and above if there are 4.
Entity 1
Entity 2
<System Name>
Entity 3

11. Worked Example Now you do Your turn - Entity 1 Entity 3
<System Name>
Now you do Your turn -

12. Your Turn
Entity 1
Entity 3
<System Name>

13. How to create a Level 0 dfd.
Add in data flow:
use a thin line with an arrow showing the way the data flows.
write the name of the data flow on the line.
Add in physical flow:
use a thick line with an arrow showing the way the physical flows.
write the name of the physical flow on the line.

14. Worked Example Now you do Your turn - Entity 1 Entity 3
<System Name>
Now you do Your turn -

15. Your Turn -
Entity 1
Entity 3
<System Name>

16. Well Done! That is how you create level 0 DFD’s

17. Tasks
Task 1
Task 2

18. What is a Level 1 dfd’s
A level 1 dfd is a diagramatic form of showing the main processes, data flows and data stores within the system.

19. How to create Level 1 dfd’s
When creating a level 1 dfd go back and read the description! (VERY IMPORTANT ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !)
Write down the following Headings:
External Entity
Processes
Data Flows
Data Stores

20. How to create Level 1 dfd’s
As you read through the passage (again) write down the relevant information under the headings above.
This will be used as a check list after creating the dfd.

21. Worked Example – School Enrolment
External Entity
Student
Processes
Record student application
Check course availability
Check student qualifications
Enrol student in course
Update application file

22. Worked Example – School Enrolment
Data Flows
Application form
Course Applied for
Student Qualifications
Results from course and student checks
Course and student details
Confirmation letter
Rejection letter
Data Stores
Application file
Course Details File
Enrolment File
Your turn – order processing

23. Your Turn – Order Processing
External Entity
Customer
Warehouse
Processes
Process customer details
Process order details
Complete picking slip
Process invoice and shipping statement

24. Worked Example – School Enrolment
Data Flows
Customer details
Order details
Picking slip
Order Copy
Invoice
Shipping statement
Data Stores
Customer File (D)
Orders Folder (M)

25. How to create Level 1 dfd’s
Processes are drawn using a Hard Box :
<process1>
Files are drawn as follows: D1
<File 1>
Data Flow is drawn the same as at level 0.

26. How to create Level 1 dfd’s
Read each sentence of the description carefully.
As you read the sentence draw that part of the dfd using the key on the previous page.
When you have finished use your checklist to make sure you have included all your processes, files etc.

27. Working Example – Student enrolment
Add application details D1
Application File
student
Application
Processing
application D2
Course Details File
Course details
rejection
letter
Checking
results
Course Details
Check course
Details
Student details
Confirmation
letter
Course Details
Check student
Qualifications
Enrolment
Process D3
Enrolment File
Student Details
Update D1
Application File
Your turn – order processing

28. Your Turn – Order Processing
Customer File
Customer
orders
Add customer
details
Customer
Details
Order
Processing M1
Order Folder
Order details
Copy of Order
Picking Slip
Complete
Picking Slip
Copy of order
Warehouse
Picking Slip
Copy of
order
Invoice
Create invoice/
Shipping statement
Shipping Statement

29. Task – school application
Now do the level 1 dfd for school application.
Way Hay – Now you can do level 1 dfd’s! Well Done!