DFD examples

Example 1 Students send in an application form containing their personal details, and their desired course. The university checks that the course is available and that the student has necessary academic qualifications. If the course is available the student is enrolled in the course, and the university confirms the enrolment by sending a confirmation letter to the student. If the course is unavailable the student is sent a rejection letter.

actions/doing words/verbs => Processes (P) .     1.  Read the problem description carefully looking for: people/organisations/things that supply information to or use information from the system => external entities (EE) actions/doing words/verbs => Processes (P) movement/exchange of information/data between external entities to processes, and processes to processes => data flows (DF) store/record information/data => data stores(DS)

2. Walk through the system in its logical sequence. A student (EE) sends in an application form (DF) containing their personal details, and their desired course The university checks (P) that the course is available. If the course is available the student is enrolled (P) in the course, and the university confirms (P) the enrolment by sending a confirmation letter (DF) that they are registered for the course to the student. Or if the course is unavailable the student is sent a rejection letter (DF).

Context diagram Highest level DFD. Has data flows, external entities, one process (system in focus) and no data stores. Shows the system boundary and interactions with external entities.   In this case: External entity - Student Process - Student Administration process application Data Flows - Application Form, - Confirmation/Rejection Letter

Context diagram

System/Level 0 DFD External entity - Student Processes - Check available - Enrol student - Confirm Registration Data Flows - Application Form - Course Details - Course Enrolment Details - Student Details - Confirmation/Rejection Letter Data Stores - Courses - Students

System/Level 0 DFD  

Hoosier Burger's food ordering system Example 2 Hoosier Burger's food ordering system The restaurant uses an information system that takes customer orders, sends the order to the kitchen, monitors the goods sold and inventory, and generates reports for management

Hoosier Burger's food ordering system The restaurant uses an information system that takes customer orders, sends the order to the kitchen, monitors the goods sold and inventory, and generates reports for management

Context Diagram Context diagram shows the system boundaries, external entities that interact with the system, and major information flows between entities and the system. NOTE: only one process symbol, and no data stores shown.

Level-0 DFD Level-0 DFD shows the system’s major processes, data flows, and data stores at a high level of abstraction. Processes are labeled 1.0, 2.0, etc. These will be decomposed into more primitive (lower-level) DFDs.

Example 3 Precision Tools sells a line of high-quality woodworking tools. When customers place orders on the company’s Web site, the system checks to see if the items are in stock, issues a status message to the customer, and generates a shipping order to the warehouse, which fills the order. When the order is shipped, the customer is billed. The system also produces various reports. Draw a context diagram for the order system Draw DFD diagram 0 for the order system

Context Diagram of Order System

Level-0 of Order System

Example 4 Perfect Pizza wants to install a system to record orders for pizza and chicken wings. When regular customers call Perfect Pizza on the phone, their phone number goes automatically into the Pizza system. The phone number invokes the name, address, and last order date comes automatically up on the screen. Once the order is taken, the total, including tax and delivery, is calculated. Then the order is given to the cook. A receipt is printed. Occasionally, special offer (coupons) is printed so the customer can get a discount. Drivers who make deliveries give customers a copy of the receipt and coupon (if any). Weekly totals are kept for comparison with last year’s performance. Draw a context diagram for Perfect Pizza Explode the context-level diagram showing all the major processes.

Perfect Pizza: Context Level Diagram Management Weekly Report Phone Number Customer Order System Customer Customer Order Customer Info Cook Delivery Person Cook Order Delivery Information

Perfect Pizza: Current Logical Level 0 Diagram Customer Customer Order Phone Number 1.0 Find Customer Record 2.0 Take Customer Order 3.0 Print Delivery Order Delivery Person Customer Information Order Information Delivery Information Customer Record Customer History Discount Info Customer Info Order Information D2 Customer History 6.0 Send Order to Cook D1 Customer Master Customer Customer Order D3 Sales Records Customer Record Sales Info Cook Order 7.0 Print Weekly Totals 5.0 Add Customer Record Weekly Report Cook Management

Perfect Pizza: Current Logical Child Diagram Customer History D2 Customer History 3.1 Determine Customer Discount Customer Information 3.2 Record Discount Discount Amount Order Information 3.3 Print Delivery Instructions Discount Information Delivery Information D3 Sales Records

Perfect Pizza: Current Logical Child Diagram 5.1 Record Customer Information 5.2 Store Customer Record Customer Information Raw Customer Information Customer Record D1 Customer Master