Question

Use Case Diagrams to model the requirements :

"A university has a Web-based coursework system, which allows students to request, complete and submit on-line coursework. Lecturers have a user_id and password. Once identified, they can submit names of their students to the system, or request student marks. Students have a user_id and password. A secure, fast and reliable service should be provided. The system checks that the student has not completed this assignment previously (i.e. that no mark is registered for this particular student and the assignment requested). If the student is eligible, the system will request an assignment from the database server. When the assignment is received, it is displayed for the student to complete. Students submit the assignment by clicking a SUBMIT button. The system processes the assignment; the result is displayed to the student and written to a file."

Answer 1

Use case diagram is the primary form of system/software requirements for a new software program underdeveloped. Use cases specify the expected behavior (what), and not the exact method of making it happen (how).

A use case diagram is usually simple. It does not show the detail of the use cases:

• It only summarizes some of the relationships between use cases, actors, and systems.
• It does not show the order in which steps are performed to achieve the goals of each use case

Use case diagrams are typically developed in the early stage of development and people often apply use case modeling for the following purposes:

• Specify the context of a system
• Capture the requirements of a system
• Validate a systems architecture
• Drive implementation and generate test cases
• Developed by analysts together with domain experts

Here are notations for diagrams.

	Use Case System function Named by verb + Noun (or Noun Phrase). i.e. Do something Each Actor must be linked to a use case, while some use cases may not be linked to actors.
	Actor Someone interacts with the use case (system function). Named by the noun. The actor plays a role in the business Similar to the concept of a user, but a user can play different roles For example: A prof. can be an instructor and also a researcher plays 2 roles with two systems Actor triggers use case(s). The actor has a responsibility toward the system (inputs), and Actor has expectations from the system (outputs).
	Boundary of system The system boundary is potentially the entire system as defined in the requirements document. For large and complex systems, each module may be the system boundary. For example, for an ERP system for an organization, each of the modules such as personnel, payroll, accounting, etc. can form a system boundary for use cases specific to each of these business functions. The entire system can span all of these modules depicting the overall system boundary
	Communication Link The participation of an actor in a use case is shown by connecting an actor to a use case by a solid link. Actors may be connected to use cases by associations, indicating that the actor and the use case communicate with one another using messages.

Our use case diagram for online coursework is as follows:

Now, for our problem, there are 5 actors. Student, lecturers, assignment, submission, and course. The lecturers teach courses give assignments and check them. The student enrolls in courses to take the assignment and submit the finished work.