Domain description:
We want to design a mailing list server, to support any number of mailing lists. Each list has one owner (the list administrator). Only the owner may designate ``senders'' --- those who are allowed to post messages to the list. The owner may or may not be a sender. Owner and senders must also be readers. For each list, there may be an unlimited number of senders. Anyone may subscribe to any list as a reader. They may also unsubscribe themselves. Assume that everything is web-based. Messages are retained for an amount of time specific to each list and consist of a subject and text. Messages should indicate sender. E-mail addresses and passwords are used for authentication purposes. Passwords may be list-specific. Because everything is web-based, e-mail is not used to send messages, ordinarily. E-mail may be used for private communication between a list owner and a reader of that list. There are no limitations as to how many lists a user may own or how many lists a user may send to. Lists have names and descriptions and exist for a fixed amount of time.
Allocate about ten minutes for each of the following activities.