The NextGen POS System Point-of-Sale (POS) system is application used to record sales and secure payment at store. System includes hardware and software -Has interfaces to various service apps, like tax calculator and inventory control, and the system should work even if access to these external services is down (i.e., at least allow checkout with cash if the credit card processing interface goes down) .Needs to support multiple client-side interface types, like thin web-browser, touchscreen, wireless phone, etc. We plan to sell this to many types of businesses which may have different business processing rules - we need flexibility and the ability to customize. (i) Construct a Use case Diagram (ii) Construct a Sequence Diagram (iii) Identify Classes and their attributes (iv) Construct a Domain Class Model