Clarification of root Classifier for a metadata record

[ejbleys]

As ISO 19115-1 is reviewed it would be appropriate to clarify which classifier(s) might be allowed as the root for metadata records. This would be independent of other classifiers being used as part of a description for objects. Currently the description against MD_Metadata in ISO 19115-1 (UML and data dictionary) is "root entity which defines metadata
about a resource or resources" is the only indicator that users should consider it as the root classifier.