2. What is a data flow diagram for?
They look at data without considering the equipment needed.
They are the first stage of designing a system.
Show what data comes from and what data is needed
3. Source of data
The OVAL = source of data (sink)
This is a source of data
e.g. order form from a customer
Or an actual person….
The user, secretary, manager etc
We are not concerned with what happens to the data before it
reaches a source, or what happens to it after it goes past it!
4. Process
The process BOX
This is a process performed on the
1
data
e.g. search, produce a graph,
Search database
perform calculation, create a mail
merge letter, print
Brief description of
process
Each process is numbered
5. Data Store
The Open Rectangle
This is where data is stored
D1 Members file
e.g. members file, letters file etc
Each store is numbered Brief description of
store
6. Direction of Data Flow
Arrows are used to show how symbols connect
e
ta bas
a
nto d
np ut i
ta ils i
De
Brief description of
data used
7. Level 0 / Context diagram
This is an overview of the whole process
Only has one process
Does not show any data stores
Book holiday
Holiday
Customer booking
system
Receipt
8. Task 1 – Create Level 0’s to show…
How a secretary in a company produces a report.
How a librarian produces a letter for overdue books.
How a doctor produces a diet sheet for a patient.
9. Draw a Level 0 diagram for your
system
Make sure that you draw the key.
Make sure you label each item.
10. Level 1 diagram
This builds on the processes involved in here
1
Book holiday
Holiday
Customer booking
system
Receipt
11. Level 1 Diagram
1
Enquiry Customer details
Availability D1 Customer records
Customer checked
List of holidays
2
Payment made Holiday details
Holiday D2 Bookings file
Customer booked
Receipt
n
rm atio
Info
k ing
3 Boo
Confirmation
Customer Printout of printed
details
