Command(A) arrives at AR(1)
    AR(1) loads its history [x,y,z]
    AR(1) executes Command(A), producing events [a,b,c]
    AR(1) writes its new history [x,y,z,a,b,c]

Events(a,b,c) are published

ProcessManager receives the events (a,b,c)
    ProcessManager dispatches Command(B) to AR(2)

Command(B) arrives at AR(2)
    AR(2) loads its own history [d,e,f]
    AR(2) executes Command(B), producing events [g,h]
    AR(2) writes its new history [d,e,f,g,h]

Events(g,h) are published