Basic and Alternative flow in use case Specification

A use case specification is a document used to capture the specific details of a use case. Use case specifications provide a way to capture the functional requirements of a system.

Create one use case specification for every use case diagram in the use case model.

The flow of events should describe the interactions between the actor(s) and the system clearly enough for an outsider to easily understand. The flow of events should represent what the system does, not how the system is design to perform the required behavior.

Flow of Events

Basic flow

• List the user action and system response that will take place during the execution of the use case under normal expected condition.
• The sequence of actions and response will ultimately lead to accomplishing the goal started in the use case name and description

Alternative Flow

• Document other, legitimate usage scenarios that can take place within the use case
• Each flow should be preceded with a scenario name
• List the user action and system responses for the alternative scenario

example:  Login

Basic flow:

• The user enters the staff id and password
• The user submits the staff id and password
• The system validate the staff id and password
• The system verifies staff id and password
• The system displays the user’s home page
• The use case end

Alternative Flow: (missing staffed and password)

• The system prompts for staff id and password
• Use case resumes at basic(main)flow step 1

(maximum 3 attempts exceeded)

• The system displays “maximum attempts exceeded contact administrator” message
• The system lock user account
• The use case ends

(invalid staff id and password)

• The system displays “ in valid staff id and password “ message
• The system prompts for staff id and password
• Use case resumes at basic flow step 1