A Petri Net is a description of the system in terms of network elements. There are four types of network elements: location, transition, entry and exit. An entrance connects the place with the transition. An exit connects the transition to a place. The net element may have zero or more annotations. Annotation can be any type of information.
For example, consider a Petri net with the following annotations of properties: 1) each element of a place has a sign (an amount that can be any number greater than or equal to zero), 2) each transition has a status (an amount that can be true or false), 3 ) each input has a status (an amount that can be true or false) and weight (an amount that can be any number greater than or equal to zero), and 4) each output has a weight (a value that can be greater than zero).
In addition, each input has a state update logic: if the input weight is greater than or equal to the location value, the status is true; otherwise the status will be false. Each transition also has a state update logic: if the state of each transition input is true, then the transition state is also true.
In addition, each input has a logic for updating the place label: the location mark (input) is equal to the value of the place minus the weight of the input. At each exit there is a logic for updating the place label: the label of the (output) place is equal to the sign of the place plus the weight of the exit. Each transition has a logic for updating the place label: call the update of the place label of each entrance and each exit of the transition.
In addition, each network element has an annotation of the graphic display: the place is a circle, the transition is a square, the input is an arrow from a circle to a square, and the output is an arrow from a square to a circle. If the place sign is 1, this is one black dot; if the place sign is 2, these are two black dots; etc. If the transition status is correct, it is green. If the transition status is incorrect, it has no color.
Most of the above annotations have been identified by several Petri Net researchers over the course of several years. Karl Adam Petri defined the elements of a network, proposed a system of annotations, and defined the first set of annotations that have practical applications. Anatol Holt coined the terms "place", "transition", "entrance", "exit" and "petri net." Holt also contributed greatly to the development of Petri nets.
I use network elements to organize requirements or computer programs. Requirements or computer programs are added as annotations to network elements.
You can consider BPMN notation as a “high level” notation that you can use to view your Petri net.