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Data Flow Diagrams
"Business process flow"not a Flow Chart
How are they developed?
• Interviews with business staff
• Observation of daily routines
• Scrutiny of paper forms, routing documents
• Research procedure manuals
• Gain understanding of processes
• Describe the flow of data in process
DFD Rules
• Always begin (or end) with a process
• All processes must produce data
• Describe data flow or business flow
• Flow left to right, top to bottom
• Do not place conditions
• Every process produces data
Example 1a
• Salesperson verifies customer's charge account when customer orders a computer
Salespersonverifiesaccount
Customer tableCustomerordersComputer
Orderrequest
Accountdata
External Entity
Business Process
Data Flow
Data Source
Example 1b
• Salesperson verifies customer's charge account when customer orders a computer, and opens a new account if necessary
Salespersonverifiesaccount
Customer tableCustomerordersComputer
Orderrequest
Accountdata
Add new account
Example 1c
• Salesperson verifies customer's charge account when customer orders a computer, and opens a new account if necessary.
• Next, salesperson verifies the computer is in inventory
• Finally, the order is entered and the computer is shipped
Salespersonverifiesaccount
Customer tableCustomerordersComputer
Orderrequest
Accountdata
Add new account
Inventory table
Invoice table
Salespersonverifies
on-hand qty
Orderdetails
Salespersoncompletesorder
itemdetails
invoicedetails