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Sending Signals from the Environment


Usually, you have to send signals into the system to make something of interest happen, for instance when the system is completely idle. You can send signals directly to a process instance, or indirectly by specifying a channel.

Sending Signals to a Process

To send a signal from the environment to a certain process:

  1. Click the Send To button in the Send Signal module, or enter the command Output-To. This command takes three parameters: the signal name, any signal parameters, and the process instance of the receiver.
  2. Select or enter the name of the signal to send.
  3. If the signal has parameters, set the values of the parameters in the dialog that is opened. Select a parameter in the list, enter/edit its value using the input line, or the option menu containing possible values (for enumeration type parameters). Click the Default value button to get a "null" value for the parameter.
  4. Select or enter the name of a process instance to send the signal to.
    The Simulator tries to find a path of channels and signal routes to the receiver. If no path was found, an error message is printed. If a path was found, the signal is either successfully sent (and placed in the input port of the receiver), or is discarded (an immediate null transition occurred), i.e. the receiver is in a state that cannot receive or save the specified signal.

Sending Signals via a Channel

To send a signal from the environment via a channel:

  1. Click the Send Via button in the Send Signal module, or enter the command Output-Via. This command takes three parameters: the signal name, any signal parameters, and an optional channel.
  2. Select or enter the name of the signal to send.
  3. If the signal has parameters, set the values of the parameters in the dialog that is opened. Select a parameter in the list, enter/edit its value using the input line, or the option menu containing possible values (for enumeration type parameters). Click the Default value button to get a "null" value for the parameter.
  4. Select or enter the name of a channel to send the signal via. If no channel is specified, any channel from the environment may be used.
    The Simulator tries to find a single process instance that can receive the signal. If no or several possible receivers were found, an error message is printed. If a single receiver was found, the signal is either successfully sent (and placed in the input port of the receiver), or is discarded (an immediate null transition occurred), i.e. the receiver is in a state that cannot receive or save the specified signal.

Causing a Spontaneous Transition

To send a "none" signal to a process, i.e. to try to cause a spontaneous transition in the process:

  1. Click the Send None button in the Send Signal module, or enter the command Output-None. This command takes one parameter: the process name. If the process contains services, it is also necessary to specify one of the services.
  2. Select or enter the name of the process to send a "none" signal to. A message is printed, indicating whether a spontaneous transition occurred.

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