Token/signaling technology of jbpm

The most important concept in jbpm should be the token and signal technology, which is everywhere in the computer network.
In the workflow engine, we can see the following: Code:
// PD is process definition and PI is process instance
Processinstance Pi = new processinstance (PD );
// Start the process
Pi. Start ();
// Get the root token
Token token = pi. getroottoken ();
// Send Signaling
Token. Signal (); the Token's signal method can also be passed in the Transition parameter. This method sends the signaling to the token, so that the token will be
Activation, and exit the current State along the specified transition (if no transition is specified, it will follow the default transition
Exit the Current Status). How does jbpm implement it? It is actually very simple:
1) the token records the current status and only the current status (or node) has this token.
2) After a signal is sent to the token, the current status receives the signal
3) The current status passes the token to the specified transition in signal.
4) After receiving the token, Transition immediately passes the token to the next state.
5) the status of the process has changed according to the position of the token.