A Tragedy of the Commons situation exists whenever two or more activities, each, which in order to produce results, rely on a shared limited resource. Results for these activities continue to develop as long as their use of the limited resource doesn't exceed the resource limit. Once this limit is reached the results produced by each activity are limited to the level at which the resource is replenished.
This is a template which one might use as a basis for creating Insight Maker Relationship models. Links have default style of the blue ones in the diagram. The easiest way to get the red dashed links is to CTRL+d to duplicate them and then connect where appropriate.