One of GoldSim’s most powerful tools is triggering, but very few modelers use anything more than the most basic OnEvent or OnTrue triggers. In this article I’ll describe and demonstrate some of GoldSim’s advanced triggering features.
Using the Semicolon in On Event Triggers
A little-known triggering feature is the semicolon in an On Event type trigger. A semicolon can be placed between links to Event-type outputs to indicate that more than one event must occur before the trigger will fire.
For example, assume that you have 3 minor events A, B, and C. Once all 3 minor events occur, a resulting event will finally occur. If Events A, B, and C are defined as timed events, this is how you might define your trigger for the resulting event:
This trigger definition indicates that Random_Event_A, Random_Event_B and Random_Event_C must occur before this element’s trigger will fire. If we were to look at the Cumulative Emitted output of the three Random_Event elements and the triggered element we would see the following:
In this realization of the simulation we see that Random_Event_C occurs first, followed by Random_Event_B. Random_Event_A is the last to occur, and since the Resulting Event element’s trigger is now satisfied, it also emits an event at the same time.
Precedence Conditions and the Required Condition Field
Whenever an On Event, On True, On False or On Changed trigger occurs, GoldSim checks two additional fields, both of which are accessed using the More button in the triggering dialog:
A Precedence Condition tells GoldSim that any triggering events must be queued until that condition is met. For example, here are Triggering dialogs for two different Triggered Event elements:
Both elements are initially triggered at 50d. They reference two different condition-type outputs (one true from 25 d onwards and the other true starting at 75d). If we plot the cumulative emitted outputs of both elements we would see the following:
Since the Precedence Condition for the first element is already satisfied at 50d, the event is immediately emitted. The second element waits until its Precedence Condition is satisfied at 75d before emitting an event.
The Required Condition field is the last item to be checked prior to the event being emitted. Again, let’s look at triggering dialogs for two different Triggered Event elements:
Both elements are initially triggered at 50d. The Required Condition field references two different condition-type outputs (one true from 75 d onwards and the other true starting at 25d). If we plot the cumulative emitted outputs of both elements we would see the following:
Since True_at_25d is true, the event that checks that condition is emitted. However, True_at_75d is false at 50d, and as a result the element with that required condition never emits an event.
Precedence and Required Conditions can be combined in the same triggering dialog. Again, here are the Triggering dialogs for two Triggered Event elements:
Both elements are initially triggered at 50d. The first element references True_at_75d as its Precedence Condition and True_at_25d as its Required Condtion. The second uses True_at_25d as its Precedence Condition and True_at_75d as its Required Condtion. If we plot the cumulative emitted outputs of both elements we would see the following:
The element that has a Precedence Condition of True_at_25d immediately checks its Required Condition (True_at_75d), which is false. As a result, that Triggered Event does not emit an event over the course of the simulation. The event with a Precedence Condition of True_at_75d waits until 75d to check its Required Condition (True_at_25d). Since this is true, the Triggered Event emits an event at 75d.
All of these features are described in depth in the GoldSim User’s Guide and in the Online Help (under Specifying Triggering Events, Specifying a Precedence Condition for a Trigger and Specifying a Required Condtion for a Trigger).