This article explains how to automatically assign a task with relevant data.
To do this, define a relevant data value and store in it the ID of the user you want to assign to the task; note that it must be of character(100) data type. The task to be assigned must have this relevant data associated in its Assign from a user in a relevant data property. Once a Workitem associated with this task is created, it will be automatically assigned to the user with the ID stored in the relevant data.
In the case of a multi-instance task, to associate each instance with a user, the relevant data must have the Dimension property set to Vector.
This function doesn't check if the user role can be assigned to the task.
HowTo: Get and Set a Relevant Data Value