In ServiceNow, the concept of domain separation allows for data and administrative segregation between different domains within an instance. When a business rule is defined in a parent domain, it applies to that domain and all child domains unless specifically overridden in a child domain1.
If a business rule is overridden in a child domain, the original rule in the parent domain continues to apply only to the parent domain and any other child domains that have not overridden the rule. The overridden rule in the child domain applies only to that specific child domain1.
Therefore, for the parent domain, the business rule that was created in the parent domain will run. The child domain's override does not affect the operation of the parent domain's business rules. This ensures that each domain can have customized behavior while still inheriting the broader rules set at the parent level.
It's important to manage these rules carefully to maintain the intended data integrity and operational workflows across different domains within the ServiceNow environment4.