Non-equivalence of entry and exit actions

S1:

<wait for next event to arrive>

switch(EventType(e#)){

case(ET1): doExitAction(S1,ET1);

break;

case(ET2): doExitAction(S1,ET2);

break;

case(ET3): doExitAction(S1,ET3);

break;

}

(Each event instance e# has an EventType(e#)=ET#.)

S2: switch(EventType(e#)){

case(ETx): doEntryAction(S2,ETx);

break;

case(ET2): doEntryAction(S2,ET2);

break;

case(ETz): doEntryAction(S2,ETz);

break;

}

<exit when next event arrives>

Warning: Entry-Action(S2,e2) and Exit-Action(S1,e2) are equivalent, since both are state and event-dependent. However, other transitions into state S2 from different sources may be caused by the same event and require different Actions

(unless the machine is also backward-deterministic).

‘Delayed’ action on exit:

‘Immediate’ action on entry:

ET2/A12

ET2/Ax2

Transitions from

other states

?

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