A Taxonomy of Event Time Representations

Abstract

A Taxonomy of Event Time Representations

Rhys Goldstein, Azam Khan

Symposium on Theory of Modeling and Simulation 2017

Terms such as “simulated time,” “simulation time,” “virtual time,” “logical time,” and “real time” appear throughout the modeling and simulation literature as a means of describing the timing, ordering, and/or processing of events. Unfortunately, this vocabulary can become a source of confusion due to subtle inconsistencies in how the terms are interpreted. Here we review mathematical representations of event times, identify their formal relationships, and present a taxonomy to clarify the proper meanings of the most common notions of time in a simulation context. For example, the taxonomy indicates that while both scalar logical time and virtual time feature a property called causal consistency, virtual time differs in that it is formally consistent with simulated time. We also argue that while simulated time is a form of simulation time, the two terms should not be used interchangeably. A thorough look at the various event time representations suggests new research opportunities, such as the repurposing of distributed computing techniques for debugging both parallel and sequential discrete event simulations.