用户登陆用例时序图

[landing successed]

[user name and password comformity]

：用户

[enter account and password]

：账户管理系统

[password incorrect]

4:reusme load

[user info non-existent]

[please register or change account]

[verify account info]

5:re-enter password

：账户信息

[case termination]

3: click to quit

：登录

[info incomplete]

[verify successed]

[return account info]

：登录页面

[generate account info]

[fill in minssing info]

1:onclick

2:onclick