Description

UML for Online Discussion Forums
Posted Fri, Oct 29
Worth 35 points (3.5% of course grade.)

In this assignment you and your partner will develop an object-oriented design and draw the UML, for the discussion forums hosted on a website.
NOTE: If you feel the impulse to ask a question about the assignment on the Forum, firstmake sure you have read this description carefully, and then read FAQs. Chances are your question is already answered here.

Online Discussion Forums
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
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
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.
Grading
Submit a single PDF file, called forums_uml.pdf, to Canvas. (Whatever software you use to draw the diagrams/write text, you MUST convert to PDF.) The PDF document should have the UML as well as the supplementary table of data structures. If you have trouble fitting the UML in one page, draw the UML with only the class names and relationships between them on one page, and then on other pages, draw the details for each entity. Hand-drawn/hand-written submissions will NOT be accepted.
Submit ONE PDF for your team, but write the names of both partners in the document.

Frequently Asked Questions
Q: Do we need to show functionality for a User to register to the website?
A: No.
Q: Can we assume that a user can only be a user of this particular forum’s website, or can these users be a part of other websites?
A: Yes, you can assume that a user can only be a user for this particular forum’s website.
Q: What’s the difference between the supplementary table of relationships and the UML Class diagram? For example, would an ArrayList implemented in a class go in the diagram as well as the table of relationships? A: As can be seen on “Slide 7–Relationship data–of the lecture notes in Week 8->uml-2.pdf”, ArrayList is not attribute in the class diagram, so it belongs to the table
Q: Does a UML diagram include constructors?
A: No.
Q: Do we need to include the following in our diagram?
“if the invitation is accepted, the new moderator replaces the current moderator”
“if the invitation is accepted, the ownership is transferred to that member”
Or is it just enough to show that the owner can send these invitations?
A: The invitation association is good enough.
Q: Does “deny or pass” imply that a message cannot be shown on the forum until reviewed by a moderator?
A: Yes.
Q: Can a user account be deleted? Can a message be deleted later on?
A: You don’t need to consider these scenarios for the assignment.