"On Simulated Time"
This paper introduces our new understandings on the semantics of simulated time. The new understandings enabled us to make two important progress in Discrete Event Simulation. First, we realized that simulation models handle simulated time in different ways, and classify them into three classes accordingly. This allows simulation s, especially large-scale complex ones, to be built in a more natural way. Second, we observed that simulated time is reversible, and came up with the concept of lookback, which greatly advanced the technique of parallel discrete event simulation.