R1

R1 / 1:1c

System is directed by zero or one Scenario

Scenario directs exactly one System

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One mode of model debugging is to run a Scenario against a System and see what happens. Alternatively, we can just load up the System and interact with it using individual debugger commands. Or we might do a combination, periodically suspending the System, poking around in it, and resuming execution while monitoring various aspects.

Consequently, the specification of a Scenario is optional, but there can be at most one loaded at a time.