The parent field for the cmdb_ci_service class is intended to only be used by SPM "service" CIs, but there is no way to know that from the CMDB metadata. There are other attributes that were added to the service class only for SPM use. I hope ServiceNow eventually realizes their mistake and moves all SPM services to their own class hierarchy (that does not inherit from Configuration Item). The use of "Service" in CSDM documents is very confusing because SPM catalog services and ITOM operational services are not clearly distinguished.
ServiceNow is using the same class to represent two different concepts (SPM Catalog Offerings and ITOM operational services). The relationships, attributes, rules and status field choice values that should only apply to either ITOM or SPM service CIs end up being active and applied to both.
For example, in ITSM forms like incident and change where it asks the user to select a Business Service, you are actually supposed to select only from a list of operational (ITOM) Service CIs (in the Application Service or Service Group classes). The Business Service(business_service) field is defined as a reference to a cmdb_ci_service (the common superclass for all ITOM Services) to enable CIs from either ITOM class can be selected.
However, the reference qualifier also lets you select SPM services because they inherit from the same cmdb_ci_service class. To prevent selection of SPM Services (which will never appear in operations and support team operational dashboards), customers will need to update the reference qualifier for the Service field on these forms to prevent selection of CIs from the Service Offerings, Business Services and Technical Services classes.
I would also update the label for the business_service form field on all these forms to "Application Service" so the end users know to select an ITOM Service.
