1. Data Flow Diagrams - Examples
And Franchise Colleges
Data Flow Diagrams - Examples
Using SSADAM Notation
By MANSHA NAWAZ
DFD - Examples

2. Context Diagram Order Company Customer Rejected Order
Despatch Note + Goods
DFD - Examples

3. Maintain Credit Ratings 2 Warehouse
A Complete DFD 1
Sales
Order
Check Credit Rating
Customer
Rejected Order D1
Credit Rating
Dispatch Note
Accounts 3
Maintain Credit Ratings 2
Warehouse
Dispatch Goods
DFD - Examples

4. Data Flow Diagrams (DFDs) show:
The processes within the system
The datastores (files) supporting its operation
The information flows within it
The system boundary
Interactions with external entities
DFD - Examples

5. A Data Flow Customer DFD Symbols SSADM Notation An External Entity
Sales 3
A Process
Check Credit Rating D1
Credit Rating
A Data Store
DFD - Examples

6. The Process Symbol Unique Number Where it’s done 3 Sales Input Data
Check Credit Rating
Output Data
What’s done
DFD - Examples

7. Maintain Credit Rating Reading
The data store symbol D1
Credit Rating
Writing/Updating
Accounts 3
Maintain Credit Rating
Reading 1
Sales
M = Manual data Store
D = Computer File
Check Credit Rating
DFD - Examples

8. Self Evident Data Flows need not be named
The Data Flow Symbol
Use Meaningful names
Customer Balance
Self Evident Data Flows need
not be named D1
Credit Rating
Sales 3
Check Credit Rating
DFD - Examples

9. Physical Resource Flow
Customer
Returned
Library Book
DFD - Examples

10. The External Entity Symbol
System Boundary
The External Entity Symbol
Customer
A Source and/or sink of data outside the system boundry
DFD - Examples

11. Levelling – to avoid complex DFDs, processes can be grouped into higher level processes2
Dispatch Goods
Process
2.1
Validated
Order 1
Dispatch
Note 2
DFD - Examples

12. Maintain Credit Ratings 2 Warehouse
A Complete DFD 1
Sales
Order
Check Credit Rating
Customer
Rejected Order D1
Credit Rating
Dispatch Note
Accounts 3
Maintain Credit Ratings 2
Warehouse
Dispatch Goods
DFD - Examples

13. Repeated Symbols – to avoid crossing lines, data
stores and external entities can be repeated:
Customer
Customer
A Duplicated External Entity D1
Credit Rating
Duplicated Data Store
DFD - Examples

14. DFD Levels Elementary Functional Description Level 2 E F D Level 1
Get cust dets
If order>cred
refer
Else
raise order
…..
E F D
Level 1
DFD - Examples

15. Wines & Spirits Example
A wines and spirits wholesaler stocks a range of approximately 400 different lines and delivers by van on regular weekly runs to customers who are mainly off-licenses and clubs. The majority of orders are received by telephone and any one customer may place several orders during the week which must be accumulated and delivered in one consignment. When a customer telephones he expects to be advised on the availability of an item requested and, if not in stock, the alternatives that are available. At present, sales order forms are filled in by the telephone salesmen and sent to the warehouse where they are used for the despatch of the items. Hand-written despatch notes are used as the basis of the invoices which are typed and sent by post sometime later.
Prepare a dataflow diagram (DFD) which represents the above system.
DFD - Examples

16. Developing Dataflow Diagrams
1. Identify external entities
2. Draw context diagram
3. Who/Where does what
4. Identify datastores
5. Draw diagram
DFD - Examples

17. External Entities Customer Context Diagram order advice customer
company
des. note + goods
invoice
DFD - Examples

18. Accumulate orders Sales Advise availability Sales
What Where/who
Receive orders Sales
Accumulate orders Sales
Advise availability Sales
Complete Sales Order Form Sales
Despatch Items Warehouse
Write despatch notes Warehouse
Type Invoices Warehouse
Send Invoices Warehouse
Datastore
Stock file
DFD - Examples

19. Draw DFD DFD - Examples customer Stock file customer Order Advice 1
Sales
Stock file M1
Accumulate orders
Advise availability
Complete forms
Sales Order Forms
Warehouse 2
Produce despatch notes
Produce Invoices
Despatch note + goods
Invoice
customer
DFD - Examples

20. Maintenance of Stock File Customer file – address, credit etc Payments
Extensions
Maintenance of Stock File
Customer file – address, credit etc
Payments
Accounts dept – invoices, payments etc
Accumulate orders – temporary file
DFD - Examples

21. Draw DFD DFD - Examples Customer 1 Sales Customers Stock file M1 M2
Order
Advice 1
Sales
Customers
Stock file M1 M2
Accumulate orders
Advise availability
Complete forms
Confirm details
Sales Order Forms
Payments
Orders M3
Warehouse M4 2
Pick Goods
Produce Despatch Notes
Update Stock File
Accounts 3
Copy Dispatch Note
Produce Invoices
Handle payments
Goods + Copy Order
Payment
Despatch Note + Goods
Supplier
Invoice
D/N + Inv M5
Customer
DFD - Examples

22. Name Alias Type Length Max Min
Data Dictionary
Name Alias Type Length Max Min
Custno Custnum Num 10
ItemDes ItemDesc Alp 20
OrdTot TotOrd Cur
e.t.c.
DFD - Examples

23. Comes in various editions to match the methodology used (SSADM)
SELECT (SSADM)
A software package for the development of data flow diagrams and data models etc.
Comes in various editions to match the methodology used (SSADM)
Check compatibility between DFD and LDS
Checks DFD level compatibility
FREE to copy from library short term loan (need to sign license agreement and get key from CEMS Help Desk)
DFD - Examples

24. SSADM Structured Systems Analysis And Design Methodology
A highly structured IS development methodology with the emphasis on analysis and design including the user but little about writing programs, testing or implementation.
DFD - Examples

25. Fastfood Example
The example below is an illustration of the data flow in a takeaway restaurant.  The order is taken on a carbon pad, the cost is calculated from the menu, the order is checked with the customer, if OK the order is stuck on a pin-board.  When the food is ready, the order becomes the delivery note for the driver.  At the close of business, carbons are used to update accounts and then dumped along with the delivery notes.  Management information is passed to the manager.
DFD - Examples

26. Fast Food Delivery System1
Meal and
Customer details
Meal and
Customer details
Record Order D1
Carbon pad
Look up meal
Customer
Price of meal 2
Record prices
Calculate
Order D2
Menu
New price
Look up prices
Details 3
Re-check
Order
Prices D3
Pin 1
Carbon details
Signature
*second copy goes on Pin2
as a backup
Manager 4
Deliver Order D4
Delivery Sheet
Name, ticket no.and price
Daily sales
Retrieve
carbon 5
Calculate
All Orders
Account Book D5
Meal total
Fast Food Delivery System
Current System
Level 1 DFD
Retrieve delivery sheet 6
Pin2 D6
Delete
All Orders
Dump carbon 7 D7
Waste Bin
DFD - Examples
Delete
Delivery Sheet
Dump delivery sheet

27. Process 1 – Record Order Details
Current System – Level 2
Process 1 – Record Order Details
Customer
Record
Meal Details
1.1 1 3
Carbon Pad D1 4 4 2
Record Customer Details
1.2 D2
Menu
Fast Food Delivery System
Current System
Level 2 DFD
Notes:
Customer gives meal details (1) and prices are looked up (2) in the menu before being added (3) to the carbon pad. Customer details such as address etc. are then added (4) to the carbon pad.
DFD - Examples

28. Process 1.1 – Record Meal Details
Current System – Level 3
Process 1.1 – Record Meal Details
1.1.1
Customer
Add New Meal to Order
Carbon Pad D1 1 1 1
1.1.2 2
Amend Order Meal Details
Menu D2 1
1.1.3
Delete Order 2
Waste Bin D6
Fast Food Delivery System
Current System
Level 3 DFD
Notes:
During a call the customer can simply add meals to her or his order which go straight onto the carbon pad. However, they could also change their mind (1) in which case new prices need to be looked up and the original carbon entry changed. They may even want to cancel the order (2). Level 2 UNCHANGED data flows are shown in blue
DFD - Examples

29. Process 1.2 – Record Customer Details
Current System – Level 3
Process 1.2 – Record Customer Details
1.2.1
Customer
Customer
Details
Add New
Customer Details
Carbon Pad D1
Changes to
Customer Details
Amend
Customer Details
1.2.2
Fast Food Delivery System
Current System
Level 3 DFD
Notes:
During a call the customer’s details – name, address etc. are added to the carbon pad. However, during the call it may be necessary to amend their details (for example, if the telephone operator has misheard the original details. Level 2 UNCHANGED data flows are shown in blue
DFD - Examples

30. Process 2 – Calculate Order Value
Current System – Level 2
Process 2 – Calculate Order Value
2.1
Customer
Meal
Details
Record Meal
Prices
Carbon Pad D1
Prices
All
Prices
Total cost
Of meal
2.2
Menu D2
Calculate Order
Value
Fast Food Delivery System
Current System
Level 2 DFD
Notes:
During a call individual meal prices are looked up in the menu and added to the carbon pad. On completion of an order the prices of all ordered meals, on the pad, are added together to give the total cost of the meal. This is then relayed to the customer.
DFD - Examples

31. Process 3 – Re-check Order
Current System – Level 2
Process 3 – Re-check Order
3.1
Customer
Meal
Details
Amend Meal
Details
Carbon Pad D1
Customer
Details
3.2
New Price
of Order
Amend Customer
Details
Menu D2
3.3
Recalculate
Order
Fast Food Delivery System
Current System
Level 2 DFD
Notes:
After an order is complete the customer may ring up to check they have given the correct details or to amend an order (forgotten the prawn crackers!) In this case details on the carbon pad are checked and amended as necessary before the customer is given the new price of the order.
DFD - Examples

32. Process 3.1 – Amend Meal Details
Current System – Level 3
Process 3.1 – Amend Meal Details
3.1.1
Customer
New Meal
Details
Add New Meal to Order
Carbon Pad D1
Changes to
Ordered Meals
3.1.2
Amend Order Meal Details
Menu D2
Customer and
Order Details
3.1.3
Delete Order
Waste Bin D7
Fast Food Delivery System
Current System
Level 3 DFD
Notes:
After an order has been taken the customer may telephone to amend order details. She could ask to add new meals or amend meals and prices will have to be looked up in the menu. Or, she can cancel the order in which case it is consigned to the waste bin.
DFD - Examples

33. Process 4 – Deliver Order
Current System – Level 2
Process 4 – Deliver Order
4.1
Customer
Complete
Delivery Sheet
Pin1 D3
Customer
Signature
4.2
Delivery Sheet D4
Obtain Customer Signature
Fast Food Delivery System
Current System
Level 2 DFD
Notes:
When the order is ready for delivery the carbon on Pin1 is used to complete the drivers delivery sheet – customer details, cost of order. On delivery of the order the customer is asked to sign the delivery sheet.
DFD - Examples

34. Process 5 – Calculate All Orders
Current System – Level 2
Process 5 – Calculate All Orders
Pin1 D3
Order
Values
Calculate
All Orders
5.1
Total
Sales
Manager
Total sales
Account Book D5
Fast Food Delivery System
Current System
Level 1 DFD
Notes:
At the close of business all orders that have been taken during the day (carbons) are taken from Pin 1 and the total value of daily business is calculated manually (using a calculator) by the Accounts person. This information is passed onto the restaurant manager.
DFD - Examples

35. Process 6 – Delete All Orders
Current System – Level 2
Process 6 – Delete All Orders
6.1
Delete Original
Copies
Pin 1 D3
6.2
Delete Duplicate Copies
Pin 2 D6
Waste Bin D7
Fast Food Delivery System
Current System
Level 2 DFD
Notes:
At the close of business all original and duplicate copies of orders (carbons) are removed from the pins and disposed of.
DFD - Examples