## 3 Proposed Approach
In this sense, the proposed strategy to improve the compactness and legibility of the model relies on encapsulating the specific evolution of the signals into the events, which will be associated with the transitions firing the sub-models characterizing the specific evolution of the signals. Those transitions will be constrained by the event's occurrence, which in turn characterizes the specific evolution of the signal and will be described through specific sub-models to be executed concurrently. The overall approach is summarized in Figure 4, where the \"IOPT input event model\" will be intrinsically considered available (without the need to be explicitly edited). Therefore, the model to be produced by the designer will be much smaller, as it will benefit from the encapsulation of the event dependencies. It is important to note that this approach will preserve the operational behavior of the initial model when executing the transformed model. This preservation aligns with the Petri net reduction techniques as presented by Murata [26], preserving the Petri net model's liveness, safeness, and boundedness properties. In addition to the already referred events, a set of new types of events are proposed. This new type of event starts considering the already defined events but imposes a specific condition that constrains their analysis. The condition to be fulfilled is that the transition to which the event is associated needs to be enabled (from the point of view of the marking) and ready (from the point of view of the non-autonomous characteristics attached to the transition). Those new types of events will have \"_Trigger_\" added to the name of the five defined events, so their names will be _UpTrigger_, _DownTrigger_, _UpOrDownTrigger_, _UpDownTrigger_, and _DownUpTrigger_. To illustrate the proposal more clearly, let us consider the UpTrigger event. Similar to the Up event, it analyzes the signal's evolution. However, this analysis occurs only after and while the associated transition is enabled and ready. This readiness is determined by the marking of the input places and the guard constrained by other signals. Figure 5b illustrates the approach: transition \(t1\) is receptive to the event _Up_ associated with signal \(a\), following the operational model of Figure 5c; similarly, transition \(t3\) is receptive to the event _UpTrigger_, which is associated with signal \(a\) and also to this specific transition \(t3\), following the operational model of Figure 5d. Regarding transition \(t3\) firing, the analysis of the signal evolution is carried on if and while transition \(t3\) is fireable. Transition \(t3\) is fireable when it is enabled (places pa and pb in Figure 5b are marked) and ready (the guard composed of signal c equals to 1 and evaluates to true). In Figure 5d (and other figures to be presented in the next sections), the evaluation of this condition is included in the notation as \(\mathit{Fireable}(t3)\) and \(\mathit{Not}(\mathit{Fireable}(t3))\). In the presented case of Figure 5d, the condition \(\mathit{Fireable}(t3)\) is evaluated by \((\mathit{pa}=1\wedge\mathit{pb}=1\wedge c=1)\). In the following two sections, events associated with Boolean signals and events associated with multivalued signals are presented. Figure 4: The overall approach relying on the introduction of events.