DFD Examples

1. DFD Examples Create a data flow diagram

2. Which way does the window face

3. How many legs do you see

4. Information flow In this task you will produce a simple data flow diagram Your task is to produce • A diagram showing the information flow when sandwiches are sold, calculations are made, there is some sort of output. • Details showing the terminators/entities, processes and data stores.

5. Ordering a tuna roll Information flow Click to move through this show.

6. The customer Tuna roll please! Ordering some lunch A customer wants to order some lunch. They walk to the counter and ask for the menu. They make their choice and ask the waitress for a tuna roll.

7. The waitresses Ordering some lunch Order 1 x Tuna roll Order 1 x Tuna roll The waitresses write this down and passes the order to the chef.

8. The chef Ordering some lunch Order 1 x Tuna roll The chef gets the order and makes the roll. The roll is then passed back to the waitress.

9. The waitresses The customer Ordering some lunch Coffee Control 1 tuna roll RM 2.99 Thank you Whilst the chef makes the roll, the waitress gives the customer a paper bill produced from the cash till. This shows how much the customer owes. The customer pays their bill.

10. The waitresses The customer Ordering some lunch When the food arrives from the chef, the waitress gives it to the customer.

11. Information flow The next few slides demonstrate how to produce the data flow diagram – this example is for ordering a tuna roll.

12. Analyse the problem • Put a square around any inputs or outputs involved - these are entities. • Circle any data stores. • Underline any processing that takes place • Sketch out the information flow, joining up the people (entities, the processing and the data stores

13. Square around inputs and outputs A customer wants to order some lunch. They walk to the counter and ask for the menu. They make their choice and ask the waitress for a tuna roll. The waitresses write this down and passes the order to the chef. The chef gets the order and makes the roll. The roll is then passed back to the waitress. Whilst the chef makes the roll, the waitress gives the customer a paper bill produced from the till. This shows how much the customer owes. The customer pays their bill. When the food arrives from the chef, the waitress gives it to the customer.

14. Circle data stores A customer wants to order some lunch. They walk to the counter and ask for the menu. They make their choice and ask the waitress for a tuna roll. The waitresses write this down and passes the order to the chef. The chef gets the order and makes the roll. The roll is then passed back to the waitress. Whilst the chef makes the roll, the waitress gives the customer a paper bill produced from the till. This shows how much the customer owes. The customer pays their bill. When the food arrives from the chef, the waitress gives it to the customer.

15. Underline any processing A customer wants to order some lunch. They walk to the counter and ask for the menu. They make their choice and ask the waitress for a tuna roll. The waitresses write this down and passes the order to the chef. The chef gets the order and makes the roll. The roll is then passed back to the waitress. Whilst the chef makes the roll, the waitress gives the customer a paper bill producedfrom the till. This shows how much the customer owes. The customer pays their bill. When the food arrives from the chef, the waitress gives it to the customer.

16. DFD Symbols External Entity Customer Chef Bill Flow of Data Process Preparing a bill Menu Data Store

17. Chef Customer Who are the ENTITIES? The customer is a source of information – the person who start the whole process off. The chef is a destination of the information. The customer and the chef are ENTITIES

18. Chef Customer Sandwich prices What is a DATA STORE The menu or price list keeps a record of prices – it is a data store. The menu is a DATA STORE

19. Order sandwich Chef Customer Sandwich prices Who is a process? The waitress processes the order The waitress is a process The waitress is not shown as an entity because she does not produce or receive information (ultimately – the order goes to the chef!!).She is not a data SOURCE or SINK!

20. Order sandwich Chef Customer Sandwich prices 1. order 5. invoice 2. order 6. payment 8. Tuna 7. receipt 9. Tuna 4. price 3. query price The arrows indicate data flows The final Data Flow Diagram

21. Before you start! A few rules to follow!!

22. Customer Chef X wrong! There must always be a process between entities!

23. Sandwich prices Customer Order sandwich Chef X wrong! Information flows must NEVER cross!

24. Assignment – CDs by mail order Bebop Records is a mail-order company that distributes CDs and tapes at discount prices to record club members. When an order processing clerk receives an order form, he or she verifies that the sender is a club member by checking the Member file. If the sender is not a member, the clerk returns the order along with a membership application form. If the customer is a member, the clerk verifies the order item data by checking the Item file. Then the clerk enters the order data and saves it to the Daily Order file. The clerk also prints an invoice and shipping list for each order, which are forwarded to Order Fulfillment.

25. Annotating the textProcessing Annotating the textData stores Annotating the textEntities

26. The end DFDs