How to get Position incumbent details in Worker Assignment Object?

Summary

How to get Position incumbent details in Worker Assignment Object?

Content

Hi,

We have an approved use case to get position incumbent details in worker Assignment object.  Need some guidance on how to achieve this.

Use Case: When manager wants to make a position change for an employee, all the positions (for the BU)are listed. We want to introduce a validation (warning) which indicates if an incumbent already exists for the selected position or not.

Status: Approved
Primary Object: Worker Assignment
Rule Type: Business Object Field Modification Rule
Oracle Comments: Note to start the rule with the following condition: