Variables: 
chan[1]: "Z" 

Event graph: 
event[0]: fork: null, #pred: 0, succ: 1 2 

# process[1]:
event[1]: send: A.X!, pid: 1, #pred: 1, succ: 
channel deps: 1 

# process[2]:
event[2]: receive: B.Y?, pid: 2, #pred: 1, succ: 
channel deps: 1 

