CS213 - Assignment 4 - UML for Online Discussion Forums - Solved

There is a website that hosts discussion forums. A person first needs to be a registered user on the website before they can participate in one or more forums. A user does not necessarily have to be a member of any forum.

 The website hosts several forums.

Each forum has one or more members.

Members of a forum can:

1.  post messages to the forum

2.   read messages posted by other members to the forum, filtered and/or sorted by message author, thread, or date filtered by author means to extract all messags posted by a specific author

filtered by thread means to extract all messags posted in a specific thread - the basis of filtering is the subject of the initiating message for that thread

filtered by date means to extract all messages posted on a specific date, or within a range of dates

sorting by author (alphabetically arranging by name) can be done on all messages in the forum, or on messages in the by-date or by-thread filtered subsets above sorting by date (chronological/reverse chronological sequencing) can be done on all messages in the forum, or on messages in any of the filtered subsets above

sorting by thread doesn't really apply - technically it's possible to sort all messages in the forum by initiating message subject, but I can't see how that would be useful

3.  leave a forum

  Each message is part of a discussion thread. It can be the initiating message for a new thread, or a response to a previous message in a thread

  Users on the website can:

1.  create new forums

2.  join an existing forum as member

  Every forum has a single owner, who is initially the creator of the forum. The creator of a forum automatically becomes its first member.

  Each forum has one moderator, who is initially the creator of the forum. Only a forum member can be its moderator.

  Owners can:

1.  invite users to join their forum by sending them an email invitation

2.  invite a member to be the moderator - if the invitation is accepted, the new moderator replaces the current moderator

3.  invite a member to take over ownership - if the invitation is accepted, the ownership is transferred to that member

4.  delete the forum

  Moderators can:

1.  deny or pass through messages posted to the forum by members

2.  resign as moderator by sending an email to the owner, at which point the owner becomes the moderator

UML
Choose the most appropriate representation for each entity in the model. (Entity here refers to class or interface.) Use interfaces and abstract classes as needed. In each class, list the key attributes and methods you determine are needed to fulfill the specification. Not all details are explicitly mentioned in the specification above, but must be filled in by inference. Such details include choice of attributes and their data types, choice of operations with parameters and return values, and choice of access levels (public/protected/package/private) for attributes and operations.

Pay special attention to the relationships between entities. Remember, super-sub classes, and interface implementations are the strongest connections between entities, followed by associations, followed by dependencies. Make sure you are as specific as you can be with the multiplicities in associations, and whether an association is a plain old link or an aggregation or a composition, whether it is bidirectional, unidirectional or reflexive. Note: Every association is by definition bidirectional unless you explicitly show unidirectionality. Make sure you show multiplicities for all associations.

Supplement to the UML
For each association, list the data structure(s) (full type definition in Java) that will be used to implement the data that arises out of the association, and name the class(es) to which it/they will belong. (Refer to Slide 7-Relationship data--of the lecture notes in Week 8->uml-2.pdf for an example. This is also emphasized in the UML Class Diagram - Part 2 video of Week 8 Lessons.) You are not required to write the class outline. Just draw a table with two columns, one for each data structure type definition, and the other for the class in which it will be defined. If the class is not either of the end points of the association, but a new class altogether, then make this fact explicit in the table.