This model notes how actors relate to each other (e.g. rabbit positively influences foxes, etc)
Expressed as a network connectivity graph: a directed graph with nodes and weighted edges.
The model itself has no state. Which is to say, it isn't affected by the engine over time. Actors do not have a status; only the relationship between actors are defined by the model.
This model's default state should be initialized from the monuments_to_relationships_logic above.
Part 2 of the Predator-Prey model. (#12)
relationship_model