In the Greta System, Signal means "communicative signal". It can be a gesture or a speech or a facial expression etc.

Typically it is generated by SignalEmitters and used by SignalPerformers.

In Greta's system, this interface describes an object that can generate Signals.

The real utilities of this interface are:

• to know which specifics objects can generate Signals
• to force the object to add or remove SignalPerformers

The SignalEmitter must send to the added SignalPerformers its generated Signals.

This interface describes an object that can receive a list of Signals.

Typicaly, the Signals are provided by SignalEmitters.

The SignalPerformer can use the transmitted Signals as it wants. But it must consider that other SignalPerformers can use the same Signals.