Stability (no unbounded oscillation) is a basic requirement, but beyond that, different systems have different behavior, different applications have different requirements, and requirements may conflict with one another.
穩定性（不會有發散性的震盪）是首要條件，此外，不同系統有不同的行為，不同的應用其需求也不同，而且這些需求還可能會互相衝突。