1. USE Case Model

2. Use-case model
The use case model captures the requirements of a system. Use cases are created based on identified functional requirements but are not mapped one-to-one to requirements
Use case models are a means of communicating with users and other stakeholders what the system is intended to do.
Use case models specify the expected behavior [what], and not the exact method of making it happen [how]
Use case models once specified can be denoted using a clear and precise visual modeling language such as UML

3. Scenarios
A use-case is made up of a set of scenarios.  Each scenario is a sequence of steps that encompass an interaction between a user and a system.  The use case brings scenarios together that accomplish a specific goal of the user.

4. Scenarios Specify behavior of use case by description, not modeling
Examples include informal structured text, formal structured text with conditions, and pseudo-code
Typically specifies:
How and when the use case starts and ends
Interaction with the actors and the exchange of objects
Flow of events: main / typical (success), alternative (success), and exceptional (failure) flows

5. Elements of a use-case description/scenario
Use Case Name: ID: Importance Level:
Primary Actor: Use Case Type:
Stakeholders and Interests:
Brief Description:
Trigger:
Relationships: (Association, Include, Extend, Generalization)
Normal Flow of Events:
Subflows:
Alternate/Exceptional Flows:

6. Actor An actor is a role that a user plays in the system.
Represent roles that humans, hardware devices, or external
systems play while interacting with a given system
They are not part of the system and are situated outside of the system boundary
Actors may be both at input and output ends of a use case

7. Examples of actors
sales person
manager
support person
web store system
It is possible that the same person may be a sales person and also provide support.  When creating a use case model, we are not concerned with the individuals, only the roles that they play.

8. Identifying Actors Define system boundary to identify actors correctly
Identify users and systems that depend on the system’s primary and secondary functionalities
Identify hardware and software platforms with which the system interacts
Select entities that play distinctly different roles in the system
Identify as actors external entities with common goals and direct interaction with the system
Denote actors as nouns

9. Use-cases
A use case illustrates the activities that are performed by users of a system.
Use cases describe the activities of a system without specifying how the activities are implemented.

10. Identifying Use Cases Business / Domain Use Cases: System Use Cases:
Interactions between users and the business (or domain)
System Use Cases:
Interactions between users and the system
One business use cases contains a set of system use cases
To name the use cases, give it a verb name to show the action that must be performed
Describe a transaction completely
No description of user interface whatsoever

11. Capture use-cases Capture use cases during requirements elaboration
Use cases are not mapped one-to-one to requirements
Each requirement must be covered by at least one use case
However, use cases may contain many requirements
Use scenarios to model assumptions and define system scope
List exceptions separately

12. Major steps in writing use-cases
Identify the major use-cases
Expand the major use-case
Confirm the major use-cases
Create the use-case diagram
As can be seen by comparing this list to figure 6-7, it is a very high level
summary. Teachers of this material might want to spend significant time reviewing
what happens in each of these steps.

13. Identifying the major use-cases
Identify the system’s boundaries
List the primary actors
List the goals of each primary actor
Identify and write the major use-cases
Carefully review use-cases

14. Expand the major use-cases
Choose one major use-case to expand
Fill in details on the use-case template
Fill in the steps of the normal flow of events
Normalize the size of each step
Describe alternate or exceptional flows
Simplify and organize as necessary

15. Confirm the major use cases
Review the current set
Consider semantics and syntax
Helpful to involve the users
Iterate the entire set of steps until all use cases are defined

16. Create the use-case diagram
Start with system boundary
Place elements in order to be easy to read
Place actors on the diagram
Conclude by connecting actors to use cases by lines

17. Use-case diagram
The use-case diagram allows a designer to graphically show these use cases and the actors that use them. 

20. Putting it all Together
When starting a use case model, it is very important to keep it simple.  Often it is easiest to first determine the actors of the system, and then flush out the use cases that they perform. 
Your use case diagrams can be as simple or complex as you wish, however simpler, less cluttered diagrams are easier to understand, and are often more powerful in capturing the tasks of the system.
Remember that a use case represents a goal of a user, not an atomic programming operation.  Your use case design should be simple and help to clarify the user's goals and expectations for the system.

21. Courseware System
Task: Create a use case model for a system that can be used to manage courses and classes for an organization that specializes in providing training. The name of the system is Courseware System.

22. The organization offers courses in a variety of areas such as learning management techniques and understanding different software languages and technologies. Each course is made up of a set of topics.
Tutors in the organization are assigned courses to teach according to the area that they specialize in and their availability.
The organization publishes and maintains a calendar of the different courses and the assigned tutor every year.
There is a group of course administrators in the organization who manage the courses including course content, assigning courses to tutors, and defining the course schedule.
The training organization aims to use the Courseware System to get a better control and visibility to the course management and to also streamline the process of generating and managing schedules for different courses.