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Data Flow Diagrams (DFDs)

Data Flow Diagrams (DFDs). Illustrate how DATA is processed by a system In terms of inputs and outputs. Analysis tool System modeling Excellent documentation tool Data flow, aka, business process Provide a way to see the pattern Systems Thinking Systems View Systems Approach.

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Data Flow Diagrams (DFDs)

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  1. Data Flow Diagrams (DFDs) Illustrate how DATA is processed by a system In terms of inputs and outputs. • Analysis tool • System modeling • Excellent documentation tool • Data flow, aka, business process • Provide a way to see the pattern • Systems Thinking • Systems View • Systems Approach

  2. Data Flow Diagrams (DFDs) - continued • Advantages for systems view, working with users: • Four simple symbols:

  3. Data Flow Diagrams (DFDs) - continued • Simple rule: • left to right, top to bottom, basically (like English) • Show all processes • data flows must start or end in a process

  4. Data Flow Diagrams (DFDs) - continued * Key: Simple Symbols Most common error: Trying to do too much

  5. DFD Example In the following example, a DFD will be created based on a paragraph about Bebop Records Co.’s method of receiving and filling orders. In this example, the information necessary to create the DFD is provided for us. In Real Life, this information comes from extensive interviewing, document gathering, and other research. .

  6. DFD Example Bebop Records is a mail-order company that distributes CDs and tapes at discount price 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 Orders file. The clerk also prints an invoice and shipping list for each order, which are forwarded to Order Fulfillment.

  7. DFD Example - Step 1 FIRST SENTENCE: Bebop Records is a mail-order company that distributes CDs and tapes at discount price to record-club members. RESULT: initial title Bebop Records

  8. DFD Example - Step 2 SECOND SENTENCE: 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. RESULT: Bebop Records Order Processing

  9. DFD Example - Step 2 continued SECOND SENTENCE: 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. RULES FOLLOWED: • left to right, top to bottom • data flows start or end in a process

  10. DFD Example - Step 3 THIRD SENTENCE: If the sender is not a member, the clerk returns the order along with a membership application form. RESULT: Bebop Records Order Processing

  11. DFD Example - Step 3 continued THIRD SENTENCE: If the sender is not a member, the clerk returns the order along with a membership application form. RULES FOLLOWED: • shows all processes without conditions

  12. DFD Example - Step 4 FOURTH SENTENCE: If the customer is a member, the clerk verifies the order item data by checking the Item file. RESULT: Bebop Records Order Processing

  13. DFD Example - Step 4 continued FOURTH SENTENCE: If the customer is a member, the clerk verifies the order item data by checking the Item file. RULES FOLLOWED: • left to right, top to bottom • data flows start or end in a process • shows all processes without conditions

  14. DFD Example - Step 5 FIFTH SENTENCE: Then the clerk enters the order data and saves it to the Daily Orders file. RESULT:

  15. DFD Example - Step 5 continued RESULT: Bebop Records Order Processing

  16. DFD Example - Step 5 continued FIFTH SENTENCE: Then the clerk enters the order data and saves it to the Daily Orders file. RULES FOLLOWED: • left to right, top to bottom • data flows start or end in a process

  17. DFD Example - Step 6 SIXTH SENTENCE: The clerk also prints an invoice and shipping list for each order, which are forwarded to Order Fulfillment. RESULT:

  18. DFD Example - Step 6 continued RESULT: Bebop Records Order Processing

  19. DFD Example - Step 6 continued SIXTH SENTENCE: The clerk also prints an invoice and shipping list for each order, which are forwarded to Order Fulfillment. RULES FOLLOWED: • left to right, top to bottom • data flows start or end in a process • shows all processes without conditions • beware of black holes - every process and data store must produce data

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