Common Mechanisms of UML

Use Case Specification: Login

• Description 
• Flow of Events 
• Special Requirement
• Pre-Conditions
• Post-Conditions
• Nodes 

Description 

• Any registered user can login 
• After clearing the verification he/she can initiate subsequent actions 
• A registered user can login and upon verification, can initiate subsequent actions

Flow of event 

Basic flow 

• The 'login' action is initiated when a registered user chooses to 'login' 
• The system prompts for username and password 
• The registered user first enters the username and password and then submits them 

Special requirements 

• The user is given three consecutive chances to login with a username/password combination. If he/she makes three unsuccessful tries consecutively, the account gets locked 
• The minimum length of password allowed is 8 characters. The password must include a combination of characters and at least one non-alphabetic character

Pre-Conditions 

• User must have an account with the library system i.e., he/she must be a registered user.

Post-Conditions 

Primary success post-condition 

• It is considered that the user is authenticated and is viewing the main page from which initiation of the additional actions can be done. 

Login failure 

• If the login fails owing to certain reasons described in the alternatives, an appropriate message will be displayed. Eventually, the user is not considered authenticated. 

Nodes 

• Until now, we have not done much with roles 
• The "appropriate message" above is vague; we need to come up with how we report this to the user 
• We must talk to security people as regards 'how reasonable it is to lock the user account after the user made some number of failed attempts. If it is made a rule, we'll need an unlock account use case