Question

Draw 1) a context data flow diagram (level-0) and 2) a level-1 diagram that shows the

appropriate details for the point of sales system described below:

Self-checkout system at Big Joe’s Supermarket uses a scanner to read universal product
bar codes (UPC). When a customer scans a product, the system reads the barcode of the
product, the product information is read by the system based on data stored in a
product file. The system displays the product summary to the customer. When the
customer provides payment information, and the system verifies the payment
information by connecting to an external credit/banking verification system. Purchases
made are stored in a file to be used in printing the receipt. After the purchase has been
made a receipt is produced and given to the customer.

Answer 1

To create the level-0 and level-1 diagrams for a point of sales system, one must consider external entities, data flows, and data stores for the overarching process and then detail each subprocess with its corresponding data flow in the more granular level-1 diagram.

Step-by-step explanation:

The student asked for two separate diagrams for a point of sales system: a context data flow diagram (level-0) and a level-1 diagram. Here's how to approach each:

Level-0 Diagram

• Determine the system of interest: the self-checkout system at a supermarket.
• Identify external entities: Customer, Credit/Banking System.
• Illustrate the main data flows: Barcodes scanned, Payment Information, Receipt.
• Define the major data store: Product File, Purchase Records.

Level-1 Diagram

1. Expand each major process detailed in the level-0 diagram.
2. Divide the single process in level-0 into subprocesses: Scanning items, Verifying payment, Printing receipt.
3. Connect subprocesses with data stores and external entities.
4. Detail the data flow between processes: Product Details, Payment Verification, Purchase Logs.

In practice, a level-0 diagram would include a single process labeled 'Self-Checkout' with data flows to and from the external entities and data stores. A level-1 diagram would break down the 'Self-Checkout' process into detailed subprocesses like 'Scan Item', 'Verify Payment', and 'Print Receipt', with more intricate data flows connecting these processes.