System chosen — Online Food Delivery System.

Level 0 DFD (Context Diagram – Food Delivery System)

This shows the system as a single process interacting with external entities.

Entities & Flows:

• Customer → sends Order Request → Food Delivery System
• Food Delivery System → sends Order Confirmation & Delivery → Customer
• Restaurant ↔ exchanges Order Details & Food ↔ Food Delivery System
• Delivery Agent ↔ gets Pickup/Delivery Info ↔ Food Delivery System
• Payment Gateway ↔ handles Payment Details ↔ Food Delivery System

🖼️ Diagram structure (Level 0)

Customer ----------------------> 
                                   \
                                    \         +-------------------+
                                     ----->   |                   |
   Restaurant <------------------->           | Food Delivery      |
                                              |     System         |
   Delivery Agent <----------------->         |                   |
                                              +-------------------+
   Payment Gateway <---------------->

Level 1 DFD (Decomposition of Food Delivery System)

Now we break down the single process into sub-processes.

Processes in Food Delivery System:

1. Browse & Select Food
   • Customer searches for restaurants/menus.
2. Place Order
   • Customer places order → order sent to restaurant.
3. Process Payment
   • System sends payment info to Payment Gateway, gets confirmation.
4. Assign Delivery Agent
   • System assigns nearest agent.
5. Track & Deliver
   • Customer can track order until delivered.

Data Stores:

• D1: Customer Database (profiles, addresses)
• D2: Order Database (order history, status)

🖼️ Diagram structure (Level 1)

                  +-----------------------------+
 Customer ------> | 1. Browse & Select Food     |
                  +-------------+---------------+
                                |
                                v
                  +-------------+---------------+
 Customer ------> | 2. Place Order              | ------> Restaurant
                  +-------------+---------------+
                                |
                                v
                  +-------------+---------------+
                  | 3. Process Payment           | <----> Payment Gateway
                  +-------------+---------------+
                                |
                                v
                  +-------------+---------------+
                  | 4. Assign Delivery Agent     | <----> Delivery Agent
                  +-------------+---------------+
                                |
                                v
                  +-------------+---------------+
                  | 5. Track & Deliver           | -----> Customer
                  +------------------------------+

✅ This covers both Level 0 (context) and Level 1 (detailed process) diagrams.