On the expressivity of the cancel construct and the temporal operator unless

A recently developed logic-based foundation of discrete event modeling and simulation asserts that making predictions entails the usage of temporal operators. The constructs of simulation languages based on the classical world views of event scheduling, activity scanning, and process interaction implement a limited functionality of the three temporal operators when, whenever, and unless. The nature of predictions that can be made using the constructs of simulation languages and the temporal operators available in the formulas of the logic-based foundation´s language L_DE are described here. The expressivity of unless is compared with that of cancel