Use Case: Registration
Trigger: To enter the details of the client
Actors: User
Main Flow: 1. User enters account name 2. System validates that the ID is not exit in the database 3. User enters password 4. User enters password again 5. System validates the passwords 6. User enters email address and phone number 7. System validates email and phone number 8. System saves the information to the user database
Extension:
2a. ID exists or less than 6 characters System returns an error warning
5a. Two Passwords are not the same System returns an error warning
5b. Password is less than 6 characters or too simple System returns an error warning
7a. email address is not available System returns an error warning
7b. Phone number is not valid System returns an error warning

Use Case: Log-in
Trigger: To enter the user Id and password to log in
Actor: User
Main Flow: 1. User enter the ID 2. User enter the password 3. System validates the Id and password 4. System allows user to log in
Extension:
3a. The Id is not exist System returns an error warning and log-in fail 3b. The password is not correct System returns an error warning and log-in fail

Use Case: Log-out
Trigger: user leave private sector
Actor: user
Main Flow: 1. User click log-out button 2. System clear the personal information and user log out successfully

User Case: Change profile
Trigger: To change the personal details or the password of the client
Actor: User
Pre-condition: Login
Main Flow: 1. User enters old password 2. User enters new password 3. User enters new password again 4. User enters new email address and phone number 5. User choose to add head portrait and other details 6. System validate the information 7. System save details to user