ensemble isn’t based on formal logic, but it’s fairly comparable to linear logic rules — character actions are specified with preconditions and effects. actions are coupled together using a call/response mechanism; the acting character (in an interaction pair) can do things to the acted-upon, but the acted-upon ultimately gets to decide the effect of the interaction.
That’s one of the things they’re trying to generalize in ensemble 2.0, integrating social practices.
Social practices are what versu is based on — informally, they’re roles and scripts (of course with room for improvisation) for social interaction, like e.g. ordering at a restaurant.
So the idea in the new version of ensemble is that you script these branching story structures for social practices, and then they can be instantiated for any character pair.]