UML activity diagram - User registration
"A registered user is one who uses a program or a website and provides his/her credentials, effectively proving his/her identity. ...
Generally speaking, any person can become a registered user by providing some credentials, usually in the form of a username (or email) and password. After that, one can access information and privileges unavailable to non-registered users, usually referred to simply as guests. The action of providing the proper credentials for a website is called logging in, or signing in." [Registered user. Wikipedia]
The UML activity diagram example "User registration" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Rapid UML solution from the Software Development area of ConceptDraw Solution Park.