This is a typical Login Page Use Case Diagram from these Business Rules converted to yUML with this yUML Use Case generator.
Use Case Diagram:

Business Rules in plain English:
{
User on Login Page
User Connect to Login Page
Login with Username & Password Extend Connect to Login Page
Remember me Extend Login with Username & Password
Fill Username if forgot Password Extend Connect to Login Page
Click on Register Extend Connect to Login Page
}
note: User on Login Page{bg:beige}
[User]-(Connect to Login Page)
(Connect to Login Page)<(Login with Username & Password)
(Login with Username & Password)<(Remember me)
(Connect to Login Page)<(Fill Username if forgot Password)
(Connect to Login Page)<(Click on Register)
Implementation Example:

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