Splitting Resource Assignments Across Multiple Time Grains in Timefold

[yuvzc]

Hello,

I'm using Timefold for resource scheduling with the TimeGrain pattern, where resources can be nurses, doctors, rooms, or equipment assigned to specific timeslots.

Use Case:
I need to handle scenarios where a single resource (e.g., a nurse) isn't available for the entire duration of a procedure. In such cases, I want to split the time allocation between multiple resources of the same type.

Requirements:

1. Primary constraint: Prefer assigning a single nurse for the entire procedure duration
2. Fallback constraint: If a single nurse isn't available, allow splitting the procedure time between 2 or more nurses

Question:
What's the recommended approach in Timefold to implement this flexible resource assignment?

Any suggestions or examples for handling split resource assignments would be greatly appreciated.

[TomCools]

Hi @yuvzc, sorry for the delay on the answer, Team Days for the Timefold Team.

Could you clarify your domain model? What are currently your variables (@PlanningVariable) and what are your entities (@PlanningEntity). Are the "timeslots" procedures?

I find your question slightly confusing since "Timeslot" is another pattern, distinct from the TimeGrain one.

[yuvzc]

Hello Tom,

Thanks for your reply

Sorry for the confusion its TimeGrain

So I have Planning Entity which is Appointment Class, Having 2 Planning variable Resource and TimeGrain.

In my solution ApointmentSolution Class I initialize my MyValueRangeProviders List resources and List timeGrains 15 min slots. Starting from a startDateTime and endDateTime.

Thanks,
Yougal

[TomCools]

Hi @yuvzc ,

In your design, an Appointment can only ever have 1 Resource (nurse). Your requirement to split a appointment across 2 nurses isn't going to work this way.

Rework to 1-to-many

In this case, there is a Many-2-Many relationship between Appointments and Resources. As per our Domain Modeling Guidelines , these should be avoided by introducing a new concept with One-To-Many relationships.

In this case, you might introduce a "AppointmentAssignment" class (PlanningEntity), which brings together the Appointment, the Resource and the TimeGrain (PlanningVariables).

This will also make it possible to add different resources (Room, Equipment, ..) to a single Appointment (through the AppointmentAssignment class).

Additional considerations

When looking at Resource and TimeGrain, there is a tight relationship between the 2 which may make it worth it to combine them into a single PlanningVariable, something like "ResourceTimeGrain". This would contain both the Resource and the Time.

• Upside: This makes it possible to only add TimeGrains for a resource when they are available. This means you will have less combinations where you'd break a "Resource is not available" constraint.
• Downside: If you have a lot of long appointments (which will need 3 (45min) or 4 (1h) timegrains), then it will be harder for the solver to find the exact ResourceTimeGrains to satisfy your "Prefer assigning a single nurse for the entire procedure duration" requirement. This may be remedied by changing the move-selectors or even implementing the custom moves>