U: Let's examine your input ("the dialogs"). What kind of line is this? "U: Let's examine the PATH. What is it?"
B: A user line.
U: That's right!
U: Which kind is this? "B: Yo"
B: A bot line.
U: Very good.
U: Which kind is this? "[Rain happens]"
B: An event line.
U: Very good.
U: How about this one? "[bla]"
B: An event line.
U: Yes
U: And this? "Usr: Let's go outside!"
B: A user line.
U: Wow you're a smart program