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The AbstractRoundBehaviour Class


For clarity, the snippets of code presented here are a simplified version of the actual implementation. We refer the reader to the Open Autonomy API for the complete details.

Whereas the AbciApp class defines the model of the FSM for the FSM App, the AbstractRoundBehaviour is a Behaviour that takes care of the processing of the current round and transition to the subsequent round, implementation of which resides in the act() method. Whenever the FSM App detects a round change, the AbstractRoundBehaviour schedules the state behaviour associated with the current round, ensuring that a transition to the new state cannot occur without first invoking the associated state Behaviour.

Below we present a sketch of this class:


class AbstractRoundBehaviour(
    Behaviour, ABC, Generic[EventType], metaclass=_MetaRoundBehaviour
    """This behaviour implements an abstract round behaviour."""

    abci_app_cls: Type[AbciApp[EventType]]
    behaviours: AbstractSet[BehaviourType]
    initial_behaviour_cls: BehaviourType

    def instantiate_behaviour_cls(self, behaviour_cls: BehaviourType) -> BaseBehaviour:
        return behaviour_cls(
            name=behaviour_cls.behaviour_id, skill_context=self.context

    def setup(self) -> None:
        self.current_behaviour = self.instantiate_behaviour_cls(

    def act(self) -> None:
        """Implement the behaviour."""
    # ...

A concrete implementation of AbstractRoundBehaviour requires that the developer provide the corresponding AbciApp, a set of BaseBehaviours encoding the different types of Behaviour at each FSM state, and the initial Behaviour. The_MetaRoundBehaviour metaclass provided enforces correctness on the logic of the AbstractRoundBehaviour ensuring that:

  • abci_app_cls, behaviour_states and initial_state_cls are set,
  • each state_id is unique,
  • initial_state_cls is part of behaviour_states,
  • rounds are unique across behavioural states, and
  • all of behavioural states are covered during rounds.

A concrete implementation of the AbstractRoundBehaviour class looks as follows:

class MyAbstractRoundBehaviour(AbstractRoundBehaviour):
    """My ABCI-based Finite-State Machine Application execution behaviour"""

    abci_app_cls: ABCIApp = MyAbciApp
    initial_state_cls: StateType = RoundA
    behaviour_states = {
    # ...
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