Entities are routed to the next activity only when the next activity is ready for it. Useful for simple just-in-time or pull systems.
1. Create the downstream activity with an Input queue of zero (0).
2. If you want the upstream activities to continue processing even though downstream capacity may be unavailable, create Output queues with sufficient size to continue processing without actually routing the entities downstream.
Example: A doctor’s office has three exam rooms and a waiting room. A check-in activity receives incoming patients and routes them to the waiting room storage. As soon as a patient leaves an exam room, another patient may be routed into that exam room.
TO DO: Create the activities, storage, and connections as shown above. In the properties dialog of the Exam activity, set the Capacity to 3 (representing three exam rooms) and the Input Queue Size to 0 (thus pulling from the Waiting storage when a patient leaves the activity).
Take a look at Produce on Demand (Make to Stock) for an example of using the Order Signal (e.g., kanban) to accomplish nearly the same thing in a different way.