2. • A data flow diagram (DFD) is a
graphical representation of the "flow" of
data through an information system.
• DFDs can also be used for the
visualization of data processing
(structured design).
• It views a system as a function that
transform the input into desired output .

3. • Flow chart shows “ flow of Control “ .
• DFD shows “ flow of Data
• The flowchart describes boxes that describe
computations, decisions, interactions &
loops.
• It is important to keep in mind that data flow
diagrams are not flowcharts and should not
include control elements .

4. • Processes on DFDs can operate in parallel (at-the-
same-time)
o Processes on flowcharts execute one at a time
• DFDs show the flow of data through a system
o Flowcharts show the flow of control (sequence and
transfer of control)
• Processes on a DFD can have dramatically different
timing (daily, weekly, on demand)
o Processes on flowcharts are part of a single program
with consistent timing

5. Creating Data Flow Diagrams
Steps:
1. Create a list of activities
2. Construct Context Level DFD
(identifies external entities and processes)
3. Construct Level 0 DFD
(identifies manageable sub process )
4. Construct Level 1- n DFD
(identifies actual data flows and data stores )
5. Check against rules of DFD

7. Creating Data Flow Diagrams
Lemonade Stand Example

8. Creating Data Flow Diagrams
Example Steps:
The operations of a simple 1. Create a list of activities
lemonade stand will be used
2. Construct Context Level DFD
to demonstrate the creation
(identifies sources and sink)
of dataflow diagrams.
3. Construct Level 0 DFD
(identifies manageable sub processes )
4. Construct Level 1- n DFD
(identifies actual data flows and data stores )

9. Creating Data Flow Diagrams
Example 1. Create a list of activities
Think through the activities
that take place at a lemonade
stand.
Customer Order
Serve Product
Collect Payment
Produce Product
Store Product

10. Creating Data Flow Diagrams
Example 1. Create a list of activities
Also think of the additional
activities needed to support
the basic activities.
Customer Order
Serve Product
Collect Payment
Produce Product
Store Product
Order Raw Materials
Pay for Raw Materials
Pay for Labor

11. Creating Data Flow Diagrams
Example 1. Create a list of activities
Group these activities in
some logical fashion,
possibly functional areas.
Customer Order
Serve Product
Collect Payment
Produce Product
Store Product
Order Raw Materials
Pay for Raw Materials
Pay for Labor

12. Creating Data Flow Diagrams
Example 2. Construct Context Level DFD
(identifies sources and sink)
Create a context level
diagram identifying the
Context Level DFD
sources and sinks (users).
Sales Forecast
Order 0.0
CUSTOMER Lemonade Production Schedule EMPLOYEE
Customer Order Product Served System Pay
Serve Product Payment Time Worked
Collect Payment Received Goods
Payment
Purchase Order
Produce Product
Store Product VENDOR
Order Raw Materials
Pay for Raw Materials
Pay for Labor

13. Creating Data Flow Diagrams
Example 3. Construct Level 0 DFD
Create a level 0 diagram (identifies manageable sub processes )
identifying the logical Level 0 DFD
subsystems that may exist.
1.0
Sale
Customer Order Sales Forecast
Customer Order
Product Ordered
Serve Product
Payment
Collect Payment 2.0 Production
CUSTOMER EMPLOYEE
Production Schedule
Product Served
Produce Product
Received Goods Inventory
Store Product
3.0
VENDOR Procure- Order
Purchase Order
Order Raw Materials ment Decisions
Pay for Raw Materials Payment
Pay Time Worked
Pay for Labor 4.0
Payroll

14. Creating Data Flow Diagrams
Example 4. Construct Level 1- n DFD
Create a level 1 (identifies actual data flows and data stores )
decomposing the processes Level 1 DFD
in level 0 and identifying
CUSTOMER
data stores.
Customer Order
ORDER
Request for Forecast
Customer Order
1.1
Serve Product Record
Collect Payment Order 1.3
Produce
Severed Order Sales
Produce Product Payment Forecast
Sales Forecast
Store Product
1.2
Receive PAYMENT
Payment
Order Raw Materials
Pay for Raw Materials
Pay for Labor

15. Creating Data Flow Diagrams
Example 4. Construct Level 1 (continued)
Create a level 1
decomposing the processes Level 1 DFD
in level 0 and identifying
Product Order
data stores.
ORDER
Customer Order 2.1
Serve Quantity Severed
Serve Product Product
Collect Payment RAW
Production
MATERIALS
Schedule
Produce Product 2.2
Store Product Produce Quantity Used
Product
INVENTORTY
Order Raw Materials Production Data
Pay for Raw Materials
2.3 Quantity Produced &
Store Location Stored
Pay for Labor Product

16. Creating Data Flow Diagrams
Example 4. Construct Level 1 (continued)
Create a level 1
decomposing the processes Level 1 DFD
in level 0 and identifying Order Decision
PURCHASE
data stores. 3.1 ORDER
Produce
Purchase
Customer Order Order Quantity On-Hand
Serve Product RAW
Quantity MATERIALS
Collect Payment Received Received
Goods
3.2
Produce Product Receive
Items
Store Product RECEIVED
ITEMS
Payment Approval
Order Raw Materials
VENDOR
Pay for Raw Materials 3.3
Pay
Vendor
Pay for Labor
Payment

17. Creating Data Flow Diagrams
Example 4. Construct Level 1 (continued)
Create a level 1
decomposing the processes Level 1 DFD
in level 0 and identifying Time Worked
data stores. 4.1 TIME CARDS
Record
Time
Customer Order Worked Employee ID
Serve Product EMPLOYEE
Collect Payment
Payroll Request
4.2
Unpaid time cards
Produce Product Calculate
Payroll
Store Product PAYROLL
Payment Approval
Order Raw Materials
4.3
Pay for Raw Materials Pay
Employe
e PAYMENTS
Pay for Labor
Payment

18. Process Decomposition
1.1 1.2
1.0
Record Receive
Sale
Order Payment
2.1 2.2 2.3
2.0
Serve Produce Store
Production
Product Product Product
0.0
Lemonade
System
3.1
3.0 3.2 3.3
Produce
Procure- Receive Pay
Purchase
ment Items Vendor
Order
4.1 4.3
4.2
4.0 Record Pay
Calculate
Payroll Time Employe
Payroll
Worked e
Context Level Level 0 Level 1