DFD Examples 1 Budget Monitoring System Departments send in their spending request to the budget monitoring system. The request is checked against the budget allocation file to ensure that the request is valid. If it is not valid, a special request is sent to management for approval. If this special request is approved by management the request is then valid. If it is not approved by management, the request is rejected and sent back to the appropriate department. Details of all valid requests are entered into the budget monitoring department’s accounts file. The valid requests stored in this file are then used to send out part orders to the suppliers. This accounts file is also used to generate monthly reports for management. 1. Draw the Context Diagram for the Budget Monitoring System described above. 2. Draw the Level 1 Data Flow Diagram for this system. 2 Goods Payment System The goods payment system in a shop buys goods from a supplier as follows: When the shop sends the system a request for goods, an order form with the order details is sent to the supplier. Details of the order are stored in the orders file. When the supplier sends a delivery note this is recorded in the delivery note file. When the supplier sends an invoice this is verified by reading the delivery note file, and then recording the details in the invoice file. Cheques are prepared by reading the invoice file, checking this against the orders file, and then sending out a check to the Supplier. 1. Based on the scenario above, draw out a table with columns for processes, sources, sinks and data stores. Your table should also indicate the input and output of each process. 2. Draw the Context Diagram for the Goods Payment System described above. 3. Draw the Level 1 Data Flow Diagram for this system. 3 Order Verification System A customer sends in an order form containing details of their order and their membership number. A check is made to verify that they are a member. When their order is verified, a check is made to validate that the items ordered are produced by the company. Next, the valid order is used to update the daily order file, and then used to create a shipping list and invoice, which are sent on to the Order Fulfilment System 1. Based on the scenario above, draw out a table with columns for processes, sources, sinks and data stores. Your table should also indicate the input and output of each process. 2. Draw the Context Diagram for the Order Verification System described above. 3. Draw the Level 1 Data Flow Diagram for this system. 4 Automatic Underground Ticket Machine The management of the Underground train service have requested an automatic ticket machine to function as outlined : The user enters their destination and ticket type into the machine (e.g. single, return or day return) and the machine calculates and displays the price. When enough money has been put in the machine issues a date-stamped ticket containing the issuing station, the destination, ticket type and price. If appropriate the machine also gives change. The machine records the details of every ticket issued and records travel statistics such as the number of tickets issued for each destination and the number of tickets of each type for each day. Once a week these statistics are transferred to the main computer. 1. Draw the Context Diagram for the Automatic Ticket Machine System described above. 2. Draw the Level 1 Data Flow Diagram for this system. 5 The Mail Order Company Plc. The sales order processing system at the Mail Order Company Plc. works as follows: As orders are received from customers by order clerks they are checked and validated to ensure that all the relevant information has been completed on the order form. If the order is incomplete then the customer is informed by post and the invalid order is not taken any further in the process. However, if an order is valid, then the customer file containing customer number, customer name, address, telephone number, credit limit etc. is checked to see if the customer is an existing customer or a new customer. If the order is from a new customer, then his/her details are added to the customer file. Next, the stock file containing item number, item name, unit price, number in stock etc. is then checked to ensure that the items on the order are in stock. If the items are not in stock, then the customer is informed and the order placed on a pending order file which contains information such as customer number, order number and expiry date. If the items are in stock, then the valid order is sent to the accounts department where it is priced with reference to the price file. The customer file is also checked to ensure that the order will not take the customer over his/her credit limit. If it does, then the customer is informed of this. Details of the amount outstanding and of the order itself are placed in the pending orders file. Where no problems are encountered, the customer and stock files are updated with respect to the order details. A dispatch note is prepared and sent to the warehouse. At the end of each week, order clerks check the pending orders file against the customer file to see if any order should now be processed. If any orders are to be processed, customers are notified. The stock file is also updated to take account of deliveries from suppliers. 1. Draw the Context Diagram for the Sales Order Processing System described above. 2. Draw the Level 1 Data Flow Diagram for this system.
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