Data Flow 1

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Data Flow 1

  1. 1. DFD Examples Create a data flow diagram
  2. 2. Which way does the window face
  3. 3. How many legs do you see
  4. 4. Information flow <ul><li>In this task you will produce a simple data flow diagram </li></ul><ul><li>Your task is to produce </li></ul><ul><li>A diagram showing the information flow when sandwiches are sold, calculations are made, there is some sort of output. </li></ul><ul><li>Details showing the terminators/entities, processes and data stores. </li></ul>
  5. 5. Ordering a tuna roll Information flow Click to move through this show.
  6. 6. 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. Tuna roll please! Ordering some lunch The customer
  7. 7. Order 1 x Tuna roll The waitresses write this down and passes the order to the chef. Order 1 x Tuna roll Ordering some lunch The waitresses
  8. 8. Order 1 x Tuna roll The chef gets the order and makes the roll. The roll is then passed back to the waitress. Ordering some lunch The chef
  9. 9. 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. Coffee Control 1 tuna roll RM 2.99 Thank you Ordering some lunch The waitresses The customer
  10. 10. When the food arrives from the chef, the waitress gives it to the customer. Ordering some lunch The waitresses The customer
  11. 11. Information flow <ul><li>The next few slides demonstrate how to produce the data flow diagram – this example is for ordering a tuna roll. </li></ul>
  12. 12. <ul><li>Put a square around any inputs or outputs involved - these are entities. </li></ul><ul><li>Circle any data stores. </li></ul><ul><li>Underline any processing that takes place </li></ul><ul><li>Sketch out the information flow, joining up the people (entities, the processing and the data stores </li></ul>Analyse the problem
  13. 13. 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. Square around inputs and outputs
  14. 14. 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. Circle data stores
  15. 15. 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. Underline any processing
  16. 16. DFD Symbols External Entity Flow of Data Process Data Store Customer Bill Preparing a bill Menu Chef
  17. 17. The customer is a source of information – the person who start the whole process off. The chef is a destination of the information. Who are the ENTITIES? The customer and the chef are ENTITIES Customer Chef
  18. 18. The menu or price list keeps a record of prices – it is a data store. What is a DATA STORE The menu is a DATA STORE Sandwich prices Customer Chef
  19. 19. Who is a process? The waitress processes the order 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! The waitress is a process Sandwich prices Customer Chef Order sandwich
  20. 20. 1. order 2. order 5. invoice 6. payment 7. receipt 3. query price 4. price The arrows indicate data flows 8. Tuna 9. Tuna The final Data Flow Diagram Sandwich prices Customer Chef Order sandwich
  21. 21. Before you start! A few rules to follow!!
  22. 22. Customer Chef There must always be a process between entities! X wrong!
  23. 23. Order sandwich Customer Chef Information flows must NEVER cross! X wrong! Sandwich prices
  24. 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. 25. Annotating the text Processing Annotating the text Data stores Annotating the text Entities
  26. 26. The end DFDs

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