i,j,k:
||tr||. i < j 
(is-send(E)(tr[i])) (is-send(E)(tr[j])) 
tag(E)(tr[i]) = tag(E)(tr[j]) tr[j] delivered at time k (
k':||tr||. k' < k & tr[i] delivered at time k' & loc(E)(tr[k']) = loc(E)(tr[k]))
is mentioned
In prior sections: mb hybrid