Explainability Service

The SES does not analyze a dataset, you rather create a request for a single activity. PSO (SES) will then list all resources and why the activity was (not) allocated to them, e.g. because of missing shifts, missing skills or simply because an allocation to that specific resource would have led to a lower plan margin.

Hi @ERCZSRHVAA ,

• The Schedule Explainability Service (SES) is used to help in understanding the Dynamic Scheduling Engine (DSE) and the decisions it has made. The service processes requests for activity and will return a result that explains why any other possible position for the activity may have resulted in an invalid schedule.
   
• This can be used to help with identifying why an activity has not been allocated or why (if it had been allocated) it was not allocated to another resource.
   
• Explanation requests can be created for an activity from the Explanations page in the Scheduling Workspace in the PSO Workbench. This page is also where the outcome of the explanation request can be viewed.
   
• Once a request is received, the SES will take a copy of the live schedule. If the requested activity is allocated, it will deallocate it from the copy. It will then attempt to allocate the activity in every single position in the schedule and report on the success of each attempt. If the attempt creates an invalid schedule, the reason for this will be included in the results. If the attempt is valid, then the difference in the plan value from the original schedule from the DSE will be included in the results.
   
• The SES does not provide explanations for why a valid attempt had a lower plan value than the original schedule.
   
• If an activity is not permitted to be scheduled to a resource, no shifts will be checked for the resource, but the reason why the resource is not allowed the activity would be returned. Similarly, if the activity cannot be scheduled to a particular shift, no positions in the shift will be checked.
   
• Further details for any attempt can be seen on this screen, with more detailed messages, information about the allocation time for the requested activity, and details about the allocation of the activity that caused the schedule to fail (which may not be the activity the request was made for).
   
• Further details on the Schedule Explainability Service and how it processed explanation requests can be found in the attached ‘Scheduling Concepts - Constraints and Preferences’ document.

Thanks and best regards,
Bhanuka

When the SES has made an attempt, and the plan value is displayed, but not shown as decreased:

Does this mean that it is still lower than the plan value currently is?

It’s not very clear as you also get this for a decreased value:

Thanks

And if it means that the Plan value would increase, why does PSO not use this plan initially?

Hi @Keith Adamson,

If the plan value difference is shown as a positive number (with the green background) then that means that this allocation produced a plan that was better than the current plan.

Ideally, with everything working perfectly, we should never see a positive plan value difference as it means that the DSE has not reached an optimal plan.

Since this is quite a simple change to make to the schedule, it is highly unlikely that the DSE has not tried it, so I think a positive plan value difference is more likely an indication of a discrepancy between how the DSE and SES have processed the routes. The processing should be identical, so something like this would probably need to be raised as an issue for us to investigate.

Thanks,

Sam