CMDB Health - Orphan CIs - How we can decide filter conditions for orphan CIs

I have to write filter condition to detect all orphan CIs. From documentation example, the filter conditions in which both the Assigned to and the Owned by fields are empty, will identify the matching CIs as orphans. What other conditions should be there for considerations of orphan CIs?

A Configuration Item (CI) is considered an Orphan based on these criteria

• The CI matches the criteria in an orphan rule.
• Required fields are missing for the CI in its respective table, or in one of its parents' table.

The orphan rules for a particular CI class and you can change these in the CI Class Manager.

• Navigate to Configuration > CI Class Manager
• Pick the CI class you want to change from the Class Hierarchy
• Check the Advanced checkbox
• Expand the Correctness section
• Click Orphan Rule

Here you define what you would like as the Orphan Rule to be for that class