Since 1998, Library Services and Content Management (LSCM) has assigned Persistent Uniform Resource Locators (PURLs) to online documents determined to be in scope of the Federal Depository Library Program (FDLP) and Cataloging and Indexing Program (C&I) and cataloged for the Catalog of U.S. Government Publications (CGP). PURLs are used by LSCM to provide a seamless user access experience.
Before October 1, 2008, LSCM used the single-record cataloging approach. All versions of a publication were cataloged on the same bibliographic record. A 530 Additional Physical Form Available Note was added to the record to indicate a digital version was available. A PURL was created for the online version of the resource and recorded in the 856 Electronic Location and Access field with indicators 41 for “version of resource.”
Since October 1, 2008, LSCM uses the separate record cataloging approach. Separate records are created for online versions, and PURLs are created and recorded in the 856 MARC field. In addition, LSCM cites the source uniform resource locator (URL) used to create a PURL at the request of Federal depository libraries. This URL is known as the “historic URL.” Since October 2017, the explanatory public note “Address at time of PURL creation” has been included with the historic URL. Since October 1, 2021, the ǂ7 - Access Status and “0” (Open access) code is added to GPO PURLs.
LSCM has used three PURL addresses:
- 1998-September 20, 2010: http://purl.access.gpo.gov/GPO
- September 21, 2010-July 30, 2017: http://purl.fdlp.gov/GPO
- July 31, 2017-present: https://purl.fdlp.gov/GPO
The identifier is the prefix of a PURL that designates LSCM as the creator of the PURL. LSCM has used three identifiers:
- 1998-2009: LPS
- 2009-2010: FDLP
- 2010-present: gpo
PURL Creation and Access
Single Part Monographs
LSCM creates one PURL for the URL where the resource resides at the time of cataloging. To ensure continued access, the PURL directs to a copy harvested and archived either on GPO’s server, GovInfo, Archive-It, official federal agency partner web site, and on rare occasions, to the live URL when information integral to the understanding of the resource is provided.
Multi-Part Monographs and eBooks
LSCM creates one PURL for the URL where the resource resides at the time of cataloging. If all parts or volumes are available at one URL, LSCM uses that URL for the PURL.
If parts or volumes are available at more than one URL, LSCM uses the first part or volume to create the PURL, and provides a landing page to collocate all parts or volumes.
If eBook versions are available at more than one URL, LSCM uses the PDF version to create the PURL, and provides a landing page to collocate all remaining versions.
If all serial issues are available at one URL, LSCM creates one PURL where the resource resides at the time of cataloging and LSCM uses that URL for the PURL.
If current and past issues are available at more than one URL, LSCM creates one PURL and directs it to the URL where the current issue is expected to always be available. LSCM creates one additional PURL and uses that URL where the earliest issue(s) are available.
If serial issues are scattered at multiple URLs, or a serial publication has ceased, LSCM provides a landing page to collocate all available issues.
Integrating Resources (IR)
LSCM creates one PURL where the resource resides at the time of cataloging and LSCM uses that URL for the PURL.
PURL is directed to a saved iteration of the resource, when available. LSCM adds a public note to indicate the PURL points to the archived version of the original resource.
When a previous iteration is unavailable, the PURL directs to the history page. LSCM adds a public note to indicate the resource is no longer available.
Formulating the 856 Electronic Location and Access Field
CGP records only contain 856 MARC fields with PURLs, and historic URLs. In rare instances, CGP records may contain 856 42 fields for a related resource.
Order of Multiple 856 MARC Fields
PURL(s) – 856 40
856 40 - PURL
Note: In records with PURLs to PDF and text versions, such as congressional publications, position the PDF PURL before the text PURL.
856 4_ - Historic URLs
856 42 - Related Resource
Historic URL – 856 4_
LSCM provides the original URL (known as the “historic URL”) used to create the PURL in an additional 856 field, which serves only as a reference in a catalog record. LSCM does not maintain, change, update, or add subsequent historic URLs.
LSCM adds a public note in subfield z of the 856 before subfield u: Address at time of PURL creation. If a PDF is obtained directly from an agency to create a PURL, a historic URL is not added in that bibliographic record. In older records, the historic URL may also be found in a 530 Additional Physical Form Available Note or 538 System Details Note.
Related Resource – 856 42
PURLs are not created for 856 42 related resource links. However, when considered important to the understanding or usage of publications, LSCM include links to the web pages of the documents that provide explanatory or contextual details. As these URLs are not maintained and some will inevitably break, LSCM uses 856 42 fields judiciously.
Public Notes – Subfield z
Public notes are added to identify resources that may no longer be available, specify software requirements, or provide navigational assistance for locating serial issues on websites or web pages.
Current practice is to place subfield z before the subfield u, but some existing records may have public navigational notes that follow the subfield u.
Materials Specified Note – Subfield 3
Designates a specific volume, part, eBook format, file format, or other detail of the resource to which the PURL or URL provides access.
When subfield 3 is present, subfield z precedes subfield 3, but some existing records may have public navigational notes that follow the subfield u.
Access Status – Subfield 7
In original and adapted records, add subfield 7 with code “0” (Open access) to PURLs for resources that meet the MARC code criteria: “The remote electronic resource is freely and openly accessible online to everyone, without restriction, login, or payment.”
In resources that do not meet the free and open access requirement, consult your supervisor for guidance.