DC.Identifier For more information . . . It is not necessary to tag all pages.
Some agencies can do nicely with only a small percentage of their pages tagged.
This is a difficult concept to define. Since the overall objective of this effort is to help end users find what they are looking for, agencies should tag the pages they want users to find. Exactly what this means depends on the agency's intent for its pages. Not all 18 tags apply to each appropriate page. If the tag does not seem to apply, you may omit it.