[tlaplus] Liveness only when a certain condition holds

[Jones Martins <jonesmvc@xxxxxxxxx>]

Hi everyone,

I'm trying to verify the following property:

ThereIsAnElection ==
  \E node \in NodeSet:
    InElection(node)

EveryoneStaysActiveDuringElection ==
  (\A node \in NodeSet:
      InElection(node) => isActive[node])

Property ==
  [](
    (/\ ThereIsAnElection
     /\ EveryoneStaysActiveDuringElection) =>
       <>ElectionWorks
  )

Which means that an election only works if no node fails during it. Yet, TLC shows me counterexamples where 'EveryoneStaysActiveDuringElection' is false. I thought that, by including it as a condition, it wouldn't appear in a counterexample. For example, I expected TLC would only show me a counterexample to Property if both ThereIsAnElection and EveryoneStaysActiveDuringElection were TRUE, but <>ElectionWorks were FALSE.

Is there something wrong in my reasoning?

Best,

Jones

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