$1.$ Domain Model Class Diagram

For the NFC subsystem, create a domain model class diagram. In Visio, this would include entities like:

NFC Transaction

Attributes: transactionID, amount, paymentType $($NFC$,$ card$),$ encryptedData

Methods: validatePayment$(),$ sendToProcessor$()$

Manager Override

Attributes: managerID, overrideType $($discount$,$ void$)$

Methods: applyOverride$(),$ logOverride$()$

User $($Manager$/$Customer$)$

Attributes: userID, NFCID, role

Methods: authenticateUser$(),$ performAction$()$

$2.$ System Sequence Diagram for UC$1$: Process Payment via NFC

The sequence diagram would include the interaction between the customer, NFC reader, and payment processor:

Customer taps NFC reader $$ NFC reader scans data $$ POS system sends data to Payment Processor $$ Payment is approved or declined $$ Transaction complete.