Connectors

Interfaces alone are not enough. Interconnections are needed to specify the flow of information. Connectors between ports can only be used in decomposed components. A port can be connected to multiple other ports of compatible direction, type, and timing.

Since the elevator and the system as a whole are the only decomposed components, we only need to add connectors in these. First, we forward the openDoor information from the elevator to the door.

Elevator.arc

package elevator;

component Elevator {
  port in boolean openDoor;

  Door door;

  openDoor -> door.shouldOpen;
}

A connector has its source on the left and target on the right. If we want to connect a subcomponent's port, we use a format of subcomponentName.portName.

Our overall system contains more than one connection. We connect all subcomponents using the corresponding ports.

ElevatorSystem.arc

package elevator;

component ElevatorSystem {
  port in int pressedOnFloor;

  Elevator elevator;
  ControlStation control;
  Motor motor;

  pressedOnFloor -> control.requestOnFloor;
  control.openDoor -> elevator.openDoor;
  motor.position -> control.motorPosition;
  control.motorCommand -> motor.command;
}

With the connectors present, we can clearly see why the controller has to have a delayed port. The connectors build a circle, also called a feedback loop, where the inputs depend on the outputs.

In the last step, we will add behavior to the remaining components, giving us a system that we can simulate and interact with.

---

A detailed decomposition reference can be found here