¢A book company receives orders by mail from customers

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¢A book company receives orders by mail from customers. The details of the book are checked for completeness (and supplemented if necessary) and the retail price determined. If the orders are prepaid the payment details are recorded and the order is forwarded for filling. If it is an account customer then the customer details are checked and discount determined. The accounts receivable are checked for excess amount owed. If credit is OK then order is filled, else prepayment is requested. To fill an order the inventory is checked and stock adjusted. If the book is available the shipping note is made and sent to the customer with the book(s) and the account customer invoiced. If the book is not available the order is placed on back order. Draw context diagram and level 0 DFD

The Correct Answer and Explanation is:

.

1. Context Diagram

Entities:

  • Customer (sends order, receives books and invoices)
  • Book Company System

Process:

  • The system receives orders and payments from customers
  • The system sends books, shipping notes, and invoices to customers

Data Flows:

  • Order from Customer → Book Company System
  • Payment from Customer → Book Company System (if prepaid)
  • Books, Shipping Note, Invoice → Customer

2. Level 0 DFD

Processes:

  1. Check Order Details
    Inputs: Order
    Outputs: Completed Order, Retail Price
    Checks completeness and determines retail price.
  2. Check Payment / Credit
    Inputs: Completed Order, Payment or Customer Details
    Outputs: Payment Confirmation or Credit Approval or Request Prepayment
    If prepaid, payment details recorded; if account customer, credit checked and discount determined.
  3. Fill Order
    Inputs: Approved Order
    Outputs: Shipping Note, Adjusted Inventory, Invoice or Back Order Notice
    Checks inventory; if available, prepares shipment and invoice; else places order on back order.

Data Stores:

  • Inventory
  • Accounts Receivable
  • Customer Details

External Entity:

  • Customer

Data Flows:

  • Order → Check Order Details
  • Completed Order → Check Payment / Credit
  • Payment Details → Check Payment / Credit
  • Credit Status → Fill Order
  • Inventory Status → Fill Order
  • Shipping Note, Books, Invoice → Customer
  • Back Order Notice → Customer
  • Updates Inventory
  • Updates Accounts Receivable

Diagram Sketch (Text-based)

Context Diagram:
[Customer] --> Order, Payment --> [Book Company System] --> Books, Shipping Note, Invoice --> [Customer]

Level 0 DFD:

(Customer)
   |
   V
[1. Check Order Details] --> Completed Order, Retail Price -->
[2. Check Payment / Credit] --> Credit Status or Payment Confirmation -->
[3. Fill Order] --> Shipping Note, Books, Invoice or Back Order Notice --> (Customer)

Data Stores:
- Inventory (queried and updated by Process 3)
- Accounts Receivable (checked and updated by Process 2 & 3)
- Customer Details (used in Process 2)

Explanation

The context diagram presents a high-level overview showing the Book Company System’s interaction with its main external entity, the Customer. Customers send orders and payments, and in return receive books, shipping notes, and invoices.

At the Level 0 DFD, the system is decomposed into three main processes that reflect the core business activities.

  • The first process, Check Order Details, ensures each customer order is complete and accurate. It supplements missing information and calculates the retail price for the requested books. This step is crucial to maintain data quality before any financial or logistical processing.
  • The second process, Check Payment / Credit, handles payment verification. For prepaid orders, payment details are recorded immediately. For account customers, the system validates customer information, determines applicable discounts, and checks the customer’s accounts receivable to ensure they do not exceed their credit limit. If the credit check fails, the system requests prepayment before continuing.
  • The third process, Fill Order, manages inventory and shipping. The system checks if the requested books are in stock. If available, it prepares a shipping note, adjusts inventory quantities, and generates an invoice for account customers. If the books are out of stock, the order is placed on back order, signaling a delay to the customer.

Supporting these processes are three data stores: Inventory holds stock information and is updated with shipments; Accounts Receivable tracks customer balances and payment history; Customer Details store customer profiles and credit status.

This structured data flow ensures orders are validated, payments verified, inventory accurately tracked, and customers appropriately billed, streamlining the company’s order fulfillment and credit management processes.

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