In the context of the interaction engine, we need to be able to define conditions guarding modifications on Entities. More specifically, we would like to be able to prevent the execution of an Action if the performing Entity is not strong enough, as an example.
We'd also like to be able to define conditions that direct the execution path of Actions. If we consider those as state machines, we want to be able to guard transitions depending on conditions such as the result of a precedent Action.