Data Flow Diagrams Level 1 and Level 0 System Design

Learning Objectives Today we will Learn: How to identify the data requirements of a IT system using a Data Flow Diagram

Notation. Data Store Process A ‘database’ which stores any information / data. This can be physical or logical (on the computer. Anything that is happening either physical / logical. This is normally someone doing something. Any person that interacts with the system logical or physical. External Entity D1 1.1

Notation (Cont) Data Flow.

Scenario 1 Flight booking system. Processes as follows: The customer makes a flight enquiry. The system returns the available flights. The customer selects a flight from the available flights. The system confirms the booking. The customer’s Payment details are sent to the system. The system issues a ticket for the flight.

Scenario The customer makes a flight enquiry. The system returns the available flights Flight Enquiry Customer Flight Enquiry Flights Flight Enquiry Available Flights Available Flights D1 1

Scenario The customer selects a flight from the available flights. The system confirms the flight is available. Check Flight Availability Customer Chosen Flight Flights Chosen Flight Flight Available Confirmation Confirmation 2 D1

Scenario The customer books the flight The system confirms the booking Book Flight Customer Chosen Flight Bookings Chosen Flight Booking Confirmation Booking Confirmation 3 D2

Scenario The customer’s payment details are sent to the system. Payments Pay for Flight Customer Payment Details The system issues a ticket for the flight. Ticket Details Flights Ticket Details Req Payment Conf Ticket Details D1 D2 4

Flight Enquiry Customer Flight Enquiry Flights Flight Enquiry Available Flights Flight Available Confirmation Check Flight Availability Chosen Flight Book Flight Customer Chosen Flight Flights Chosen Flight Booking Confirmation Payments Pay for Flight Payment Details Payment Details Ticket Details

Context Diagram A context diagram, a simple representation of the whole system. It is a simplified version of level 1 diagrams Only shows 1 process, which is the whole system.

Context Diagram Customer Flight System: Flight Enquiry, Flight Availability, Book Flight, Pay for Flight 0 D1Flights D2Payments Flight Enquiry Available Flights Flight Available Confirmation Chosen Flight Flight Enquiry Available Flights Chosen Flight Payment Details Payment Conf THE DATA FLOWS MUST MATCH THE LEVEL 1

Scenario - Cinema The customer makes a film enquiry by entering a film name. The system returns the available flights Film Enquiry Customer Film name Films Film Name Available Times Available times D1 1

Scenario - Cinema The customer selects a film + time from the available films The system confirms the flight is available. Check Films Availability Customer Chosen Film + Time Films Chosen Film + Time Film Availability Confirmation 2 D1

Make an order Add a product Add a supplier Search for product Search for order Search for supplier.

Page 81 Draw a Level 1 Diagram for Westford Stationary Ltd. Make an order Add a product Add a supplier Search for product Search for order LO: To understand what a DFD is, and to create a level 1 and level 0 DFD.

Page 79 Draw a Level 0 Diagram for Westford Stationary Ltd. Do it on blank paper if needed.