UML (Unified Modeling Language) is a standard language for specifying, visualizing, constructing, and documenting the artifacts of software systems. UML was created by the Object Management Group (OMG) and UML 1.0 specification draft was proposed to the OMG in January 1997. It was initially started to capture the behavior of complex software and non-software system and now it has become an OMG standard.

Use Case:

Use case plays a significant role in the distinct phases of Software Development Life Cycle. Use Case depends on ‘User Actions’ and ‘Response of System’ to the User Actions.

It is the documentation of the ‘Actions’ performed by the Actor/User and the corresponding ‘Behaviour’ of the System to the User ‘Actions’. Use Cases may or may not result in achieving a goal by the ‘Actor/User’ on interactions with the system.

In Use Case, we will describe ‘How a System will respond to a given Scenario?’. It is ‘user-oriented’ not ‘system oriented’.

It is ‘user-oriented’: We will specify ‘what are the Actions done by the user?’ and ‘What the Actors see in a system?’.

It is not ‘system oriented’: We will not specify ‘What are the input given to the system?’ and ‘What are the output produced by the system?’.

The development team needs to write the ‘Use Cases’, as the development phase highly depends on them.

Use case writer, Team members, and the Customers will contribute towards the creation of these cases.

For creating the these, we need to have a development team assembled and the team should be highly aware of the project concepts.

After implementing the case, the document is tested, and the behavior of the System is checked accordingly. In a case the capital Letter ‘A’ denotes ‘Actor’, the letter ‘S’ denotes ‘System’.

Elements in Use Cases

1) Brief description: A brief description explaining the case.

2) Actor: Users that are involved in Use Cases Actions.

3) Precondition: Conditions to be Satisfied before the case begins.

4) Basic Flow: ‘Basic Flow’ or ‘Main Scenario’ is the normal workflow in the system. It is the flow of transactions done by the Actors on accomplishing their goals. When the actors interact with the system, as it’s the normal workflow, there won’t be any error and the Actors will get the expected output.

5) Alternate flow: Apart from the normal workflow, a system can also have an ‘Alternate workflow’. This is the less common interaction done by a user with the system.

6) Exception flow: The flow that prevents a user from achieving the goal.

7) Post Conditions: The conditions that need to be checked after the case is completed.

Use Case Diagram

Use Case Diagram is a pictorial representation of a user(s) Actions in a system. It does provide a great tool in this context, if the diagram is containing a lot of actors, then it is very easy to understand. If it is a high-level diagram, it won’t share a lot of details. It shows complex ideas in a fairly basic way.

As shown in the Fig above it represents a diagram where Rectangle represents a ‘System’, oval represent a ‘Use Case’, Arrow represents a ‘Relationship’ and the Man represents a ‘User/Actor’. It Shows a system/application, then it shows the organization/people who interact with it and shows the basic flow of ‘What the system does?’

This is the Use case diagram of ‘Login’ case. Here, we have more than one actor, they are all placed outside the system. Students, teachers, and parents are considered as primary actors. That is why they all are placed on the left side of the rectangle.

Admin and Staff are considered as secondary actors, so we place them on the right side of the rectangle. Actors can log in to the system, so we connect the actors and login case with a connector.

Other functionality found in the system are Reset Password and Forgot password. They are all related to login case, so we connect them to the connector.

EXAMPLE 1: Write the scenario for user interaction with ATM system.

EXAMPLE 2: Write the steps for booking a ticket in a reservation.