R16

R16 / 1:1c

System Input is initiated by zero or one Input Source

Input Source initiates exactly one System Input

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When we inject input into a System, the source of that input need not be an Actor. We may choose to set the value of some instance's attribute or force that instance into some state, for example. In doing so, we have a target (the instance) but no source other than the debugger itself, which is not an Actor.

An Actor playing the role of an Input Source must, by definition, initiate a System Input interaction.