URNs:
- Uniform Resource Names - make identification of
Internet documents possible.
- URN identifiers are persistent and unique.
- See <URL:http://www.ietf.org/html.charters/urn-charter.html>
PURLs:
- Persistent URLs
- Points to a resolution services rather than the resource itself.
- See <URL:http://purl.oclc.org/>
