Standards:Preservation

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THO Standards for Cultural Heritage Digitization Projects

Preservation Standards

Introduction

Preservation management of digital materials is not a new field. It had its origins in the 1970's, when government agencies were already discovering the rapid rate of obsolescence of digital data. As computer technology has matured, this rate of obsolescence has decreased, but the amount of both "born digital" and digitized materials, and the institutional importance of those materials, has increased dramatically.

In addition to the desire to promote continued accessibility, defined by the Digital Preservation Coalition as the "continued, ongoing usability of a digital resource, retaining all qualities of authenticity, accuracy and functionality deemed to be essential for the purposes the digital material was created and/or acquired for," institutions may be legally required to provide access to both "born digital" and digitized materials under the Texas Public Information Act and the U.S. Freedom of Information Act. This legal mandate for continued access is in sharp contrast to the efforts of the private sector to promote Digital Rights Management (DRM) systems that limit access to digital materials.

Preservation management of digitized materials has largely been derived from preservation management practices for physical materials. This is the origin of the widely-held "scan once" preservation practice. While this may be appropriate for some materials and collections, it is becoming increasingly apparent that digital preservation practices for digitized materials may in some cases require re-digitization of individual items and collections in order to maintain accessibility. It is to be hoped that as the available resolution and color depth of scanning equipment approaches the theoretical limits of photographic processes, the need for redigitization of original source materials will decrease.

There are three common strategies for digital preservation: preservation, emulation, and migration. Preservation typically involves maintaining the original hardware and software used to create the digitized material; for material that is presented via the World Wide Web, this may require maintenance of older browser versions and plug-ins or helper applications. Emulation is a strategy that requires the creation of a "virtual machine" or software tool that will allow older software to run on newer hardware and operating system. It may also include the development of software that maintains backward-compatibility with older formats. Migration is the best and most expensive option; as new formats, software, and hardware appear, materials should be recreated or resaved. Projects working to develop best practices using these various strategies include the Cedars and CAMiLEON projects, both completed, and the MIDESS project.

There are many good sources for information about preservation management. The Northeast Document Conservation Center's Handbook for digital projects: A management tool for preservation and access contains excellent overviews and practice information, including information about vendors, though some of the information needs to be updated. The Digital Preservation Coalition, National Library of Australia, and the PADI Gateway regularly maintain and update their Preservation Management of Digital Material Handbook, which is also available in the 2001 print edition, written by Maggie Jones and Neil Beagrie.

Levels of Preservation Management

THDI recognizes three levels of standards for preservation management of digitized materials:

Minimal

Participants will use non-proprietary formats whenever possible and will minimize the use of tools for digital rights management (DRM) that may in the future affect the accessibility of their digital collections. Participants will regularly evaluate the accessibility of their collections and will remove, refresh, or recreate collections as they find necessary and practical. Participants will store materials on at least two physical drives, a server and a backup.

Basic

Participants will identify items with medium to long term access requirements and develop preservation management plans for those items and collections. Participants may choose to use the ERPANet "Digital Preservation Policy Tool" in developing those plans. Participants should include plans for adding those materials as appropriate to a trusted digital repository, as defined by the RLG and OCLC 2002 report on attributes of trusted digital repositories, which has been further developed in the 2004 PREMIS Working Group report on implementing preservation repositories. Participants will store materials in at least two media maintained in separate physical locations and will regularly refresh the media as needed to preserve the content, using information and best practices for sustainability of digital formats and media developed by the Library of Congress and the National Digital Information Infrastructure and Preservation Program (NDIIPP).

Enhanced

Participants will meet the requirements of trusted digital repositories, as defined by the RLG and OCLC 2002 report on attributes of trusted digital repositories, which has been further developed in the 2004 PREMIS Working Group report on implementing preservation repositories. Participants will use a digital asset management system that conforms to the OAIS reference model and will develop and use preservation metadata as required by the OAIS reference model as implemented in the PREMIS "Data Dictionary for Preservation Metadata." Participants may choose to become involved in the National Digital Information Infrastructure and Preservation Program (NDIIPP) coordinated by the Library of Congress.

References

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