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 Salesperson verifies account Customer table Customer orders Computer Order request Account data 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 Salesperson verifies account Customer table Customer orders Computer Order request Account data 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

Salesperson verifies account Customer table Customer orders Computer Order request Account data Add new account Inventory table Invoice table Salesperson verifies on-hand qty Order details Salesperson completes order item details invoice details