Namespace definition is missing in delivery request

What causes this issue?

Namespace definitions are missing in the delivery request for the
namespaces of the objects contained in the delivery request. For a
complete delivery request of type installation/upgrade, SAP recommends
that you use the namespace definitions in the delivery request.

System Response

The system returns the affected entries in the results overview of the
object list check.

How to fix this error?

Transport the namespace definitions to the consolidation or final
assembly system, and include the change request in the delivery.
Then run the check again.

Error message extract from SAP system. Copyright SAP SE.