on-line simulation in the ops system
OPS is an interactive system designed for general use in a time-sharing environment. It includes an on-line capability for building models and running simulations. Simulation activities are scheduled, canceled, or rescheduled dynamically on an AGENDA either at a specified time or when a prescribed condition is met. Activities can be made to consume simulated time by means of a delay for a certain period or a wait until given conditions are satisfied. The AGENDA is a time-ordered list of conditionally and unconditionally scheduled activities. Working within the multi-purpose framework of the OPS system, the user may inspect the AGENDA or some index of performance without stopping the simulation. He can also interrupt the run to make unprogrammed inspections and alterations. Before resuming, he can roll the simulation back to an earlier state that has been preserved, or perturb it in some other manner. Reference to data and activities is symbolic.
simulation systems interactive system general use timing environments model activation scheduling user inspection indexing performance data sharing  framework 