This model illustrates the localization of Zeno conditions in the Distributed Discrete Event (DDE) domain. The demo consists of two topologically identical branches connected to a clock source actor. Each branch contains a feedback loop and is fed identical tokens from the clock source. As with all feedback loops in DDE (and DE) models, a positive time delay is necessary in feedback loops to prevent deadlock. If the time delay of a given loop is lower bounded by zero but can not be guaranteed to be greater than a fixed positive value, then a Zeno condition occurs in which time will cease to advance even though the actors of the feedback loop continue to execute without deadlocking.
In centralized discrete event systems, Zeno conditions prevent progress in the entire simulation. This is true because the feedback cycle experiencing the Zeno condition prevents time from advancing in the entire model. In contrast, distributed systems localize Zeno conditions as much as possible based on the topology of the system. Thus, as shown in the demo above, a Zeno condition can exist in one section of a topology without impacting the entire system.
In the model, the bottom branch experiences a Zeno condition as soon as time advances to 45. This causes the the bottom branch to continue execution long after the top branch has ceased execution, even though the clock source sends identical data to both branches.