R2

R2 / 1:M

Scenario plays out as a seqeuence of one or many System Interaction

System Interaction occurs in exactly one Scenario

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We define a Scenario as a series of interactions with the target System. At the very least there might be a single stimulus ([System Input]) that initiates activity in the System. In any case, there must be at least one System Interaction for the Scenario to have any utility.