External pointers to digital objects include MARC record 856 fields, HTML hypertext links (HREFs), and Encoded Archival Descriptions (EADs).
Such pointers can contain one of the following:
* In MARC record 856 fields the "g" subfield is used to hold URNs and the "u" subfield is used to hold URLs. For current LC plans for using 856 subfields g and u, click here.
Uniform Resource Name (URN)
- URN tag
- A colon [:]
- Name Space Identifier (e.g. hdl, isbn)
- A colon [:]
- Local Object Identifier (e.g., a handle or ISBN)
URN tag:Name Space ID:Local Object ID
- The URN is resolved by a specified server into one of the HTTP Uniform Resource Locator types listed below.
HTTP Uniform Resource Locator (URL)
Protocol ID://Host name:Port ID/Path?Search Argument
Protocol ID://Host name/Path?Search Argument
Protocol ID://Host name:Port ID/Path/Object Name
Protocol ID://Host name/Path/Object Name
HTTP Uniform Resource Locator (URL) where the Local Object ID contains a URN and the host/domain name is that of the server to be used in resolving the URN to a URL.
Protocol ID://Host Name of Resolver:Port ID/Local Object ID
Protocol ID://Host Name of Resolver/Local Object ID
LC Plans for Using MARC 856 subfields g and u:
Ultimately, the Library of Congress will record the Uniform Resource Name (URN) in the 856 field of the MARC bibliographic record associated with an LC collection item that has been digitized. Such URNs will be constructed as "handles" and will be placed in subfield g (856 $g). Example: $gurn:hdl:loc.ndlp/amrlp.3a16116
In the near term, however, both URLs and URNs will be recorded in the 856 field:
|Created: 9/12/97 Revised: 02/09/98|
|National Digital Library Program - Digital Repository Development Project|