Consider an online reservation system (TRS) for a travel company. TRS will initially offer services for travel by bus, train, and airplane. However, in the future, they plan to extend their offerings by cruises in the Mediterranean. Each trip starts from a certain source city and ends in a different destination city, with possible stops in between. Each carrier (bus, train or airplane) is identified by a unique ID (e. g., its plate for a bus). The trips are based on a predefined schedule and they optionally stop at predefined stations/cities. Each carrier can have only one trip per day. Each carrier includes one or two drivers and up to 10 hostesses for each trip depending on the carrier capacity. There are two types of trips, normal trips and express trips. Express trips do not stop at intermediate stations and get faster at the destination. The customers can make reservations (with a certain time option to buy) and purchase tickets on the web site of the company using TRS. However, the company won't offer a call center to help out customers to reduce costs as everybody has access to the Internet these days. Reservations not purchased by the option date are cancelled automatically by TRS. The customer can pay for the seat through the website before the specified option date. The option dates are to be determined by a dedicated optimization module of TRS. The price of each trip is fixed; however, the company may sell up to a certain number of seats in each trip with a promotion price with feedback from the marketing department. Changes and cancellations are possible for flexible tickets only, with certain penalties as determined by the company for each trip. The assignments of the personnel to trips are done by company staff in operations department, at most one week before each trip using TRS. For this purpose, TRS will again use the aforementioned optimization module, taking into account the personnel's time-off days and holidays. Such information is to be entered into the system by the human resources department of the company since drivers and hostesses don't have access to and won't use TRS. The accounting of payments will be handled by a previous software system, used by the company for a number of years. Both the customers and the company staff must authenticate themselves for performing operations with TRS. (a) Draw a use case diagram for describing the functional requirements of the above system.
(b) List and provide rationale for three design goals for the above system. Briefly discuss if any two of them are in conflict.
(c) State and justify an architectural style that can be used for the above system
(d) Draw a draft object design for the above system such that it can support implementation of all the features specified above for only entity objects.