In workflows, an object cannot be in a state without an assignee being set. This regardless of whether the state represents a human task or not. The assignee must be an existing STEP User or user group.
An important thing to notice when working with assignees is that users who do not have the 'STEP Workflow Administrator' privilege for a given workflow only will be able to view tasks assigned to themselves or a group they are a member of. Furthermore, they will only be able to work with tasks assigned directly to themselves and have to claim a task (i.e., assign it to themselves) to be able to edit workflow related data and perform transitions. Users with the 'STEP Workflow Administrator' privilege can view and work with all tasks regardless of who they are assigned to.
Note: For states that do not represent a human task, you will typically want the assignee to be either an administrator with in-depth knowledge about the workflow or a dedicated 'automation' dummy user.
There are multiple ways of setting the assignee for a state. In the sections below, the options in the Workflow Designer State Editor are described.
For setting the assignee using the On Entry tab in the State Editor, refer to the Assigning Tasks Using Business Rules topic in the Advanced Workflow Topics section of the Workflows documentation here.
For more on retrieving user IDs who work with tasks in workflows, refer to the Retrieving the ID of an Assignee Completing a Task in a Workflow in the Advanced Workflow Topics section of the Workflows documentation here.
Note: Attempting to delete a user who an assignee for a workflow state will result in errors. For more information, refer to the Working with Users topic in the System Setup documentation here.