hscale=auto;
a, b, c, d;
a->b-|: Goes to out there;
|->c-d: Comes from out there;
->d start before b: 
    Start further before
    [arrow.starttype=dot];
---;
a->b: Trigger Msg;
b-> end after b;
b-> end after b +10;
b-> end after b +20;
---;
b<- start before b;
b<- start before b +10;
b<- start before b +20;
b->a: We got them all;

