check funtion and password show in UML

I am a real beginner in UML and I've got a 2 (simple) cases, which I am not sure if I do it right (my possible solution is insterted):

First one:
Person X is registering in a database that he send a letter to person Y.
If person Y received the letter, he should confirm this by check a box behind the register information (made by Person X).

Second one:
Somebody has to log into a system with a loginname and password/

How can I show this in UML?

Possible solution first case(?):
There is a class "Person" and a class "Letter". Should I draw just these two classes with a normal association and add special operations? Or should I add a remark which explains the situation?

Possible solution second case(?):
Just use the class "person" with attributes loginname and password with operations like insertLogin, insertPassword, checkPassword. Or something?

Thnx for helping me!

Regards,
Frederique van Amelaan
Frederiquevanamelaan_at_hotmail.com Received on Mon Jul 29 2002 - 07:57:36 CEST