Data%20Flow%20Diagrams

1
Data Flow Diagrams

• "Business process flow"not a Flow Chart

2
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

3
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

4
Example 1a

• Salesperson verifies customer's charge account
  when customer orders a computer

Data Flow
CustomerordersComputer
Salespersonverifiesaccount
Orderrequest
Accountdata
Customer table
Data Source
Business Process
External Entity
5
Example 1b

• Salesperson verifies customer's charge account
  when customer orders a computer, and opens a new
  account if necessary

CustomerordersComputer
Salespersonverifiesaccount
Orderrequest
Accountdata
Customer table
Add new account
6
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

7
Orderdetails
Add new account
Salespersonverifieson-hand qty
itemdetails
Inventory table
Salespersoncompletesorder
invoicedetails
Invoice table