Context Diagram Practice

Unit 3 - System Analysis & Design

Instructions

Draw context diagrams using Yourdon/DeMarco notation. Remember: rectangles for external entities, circle for the system, arrows showing data flows with labels.

Symbol Reference

Entity
External Entity (rectangle)
System
System (circle)
data
Data Flow (arrow with label)

Question 1: Library System (4 marks)

Read the scenario and draw a context diagram in the space provided:

Scenario: A library system allows members to search for books and borrow items. The system sends overdue notices to members. Librarians can add new books, update member details, and generate reports. The system orders books from suppliers and receives delivery confirmations.

Identify the components:

External Entities:

Data Flows (list at least 4):

Draw the context diagram:

Question 2: Online Food Ordering (4 marks)

Scenario: An online food ordering system allows customers to browse menus, place orders, and make payments. Restaurants receive orders and update order status. Delivery drivers receive delivery assignments and report delivery completion. The system sends order confirmations and delivery updates to customers.

Identify the components:

External Entities:

Data Flows (list at least 5):

Draw the context diagram:

Question 3: Identify Errors (3 marks)

The following context diagram has 3 errors. Identify and explain each error:

Customer Booking System Hotel booking

Error 1:

Error 2:

Error 3:

Question 4: Short Answer (3 marks)

a) What is the purpose of a context diagram? (1 mark)

b) Why are data stores NOT shown on a context diagram? (1 mark)

c) What is a Data Flow Diagram (DFD) Level 0, and how does it differ from a context diagram? (1 mark)

View Answer Key (for self-marking)
Q1 Entities: Members, Librarians, Suppliers. Flows: search request, book details, borrow request, overdue notice, book order, delivery confirmation, member details, reports
Q2 Entities: Customers, Restaurants, Delivery Drivers. Flows: menu request, order, payment, order confirmation, delivery assignment, delivery status, order updates
Q3 Errors: 1) Customer not in rectangle, 2) System should be circle not rectangle, 3) Data flow from Customer has no label
Q4a: Shows system boundary and how it interacts with external entities at a high level
Q4b: Context diagrams show external interactions only; data stores are internal to the system
Q4c: DFD Level 0 is often the same as context diagram; Level 1+ shows internal processes
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