The key elements of the UCD are:

Actors:

Prospective Customer $($PC$)$

Registered Customer $($RC$)$

Restaurant $($R$)$

Delivery Driver $($DD$)$

Use Cases:

Create Account $($UC$1)$

View Menu $($UC$2)$

Place Order $($UC$3)$

Process Payment $($UC$4)$

Notify Restaurant $($UC$5)$

Assign Delivery $($UC$6)$

Notify Driver $($UC$7)$

Pick Up Order $($UC$8)$

Deliver Order $($UC$9)$

Verify PIN $($UC$10)$

Relationships:

The "Prospective Customer" initiates the "Create Account" use case.

The "Create Account" use case leads to the "Registered Customer" actor.

The "Registered Customer" uses the "View Menu" and "Place Order" use cases.

The "Place Order" use case triggers the "Process Payment" use case.

The "Process Payment" use case triggers the "Notify Restaurant" use case.

The "Notify Restaurant" use case triggers the "Assign Delivery" use case.

The "Assign Delivery" use case is used by the "Delivery Driver" actor.

The "Notify Driver" use case is triggered by the "Assign Delivery" use case.

The "Delivery Driver" uses the "Pick Up Order" and "Deliver Order" use cases.

The "Registered Customer" uses the "Verify PIN" use case, which is used by the "Delivery Driver".