The claim itself is fine because it is kind of tautological. An error that cannot be observed in any way is probably not an error. However, you have to prove th

The claim itself is fine because it is kind of tautological. An error that cannot be observed in any way is probably not an error. However, you have to prove that it can't be observed. This is quite different than what the described system does though. The system flags errors that have been observed. The correct claim to go with what the article does would thus be: > For any anomaly in a stateful service, it is an anomaly only if the current clients running their current operations happen to observe it. Otherwise, we argue that it doesn't matter at all. It's much more noticeable this way, isn't it?