The Preservation of Digitized Reproductions
Approved by the Society of American Archivists Council June 9, 1997
The digital world challenges our notion of preservation. Traditional preservation, as responsible custody, works best when evidence of human activity can be touched and sensed directly, when the value of the evidence exceeds the cost of keeping it, and when the creators, keepers, and users of the evidence work cooperatively toward the same ends. While this evidence is traditionally seen as documents on paper, increasingly archivists must preserve a variety of formats, including still and moving images and sound recordings. All of these media can now be reproduced in digital form. Such digital information cannot be used without the help of a machine. World-wide access through the Internet raises many questions about who owns digital information, who has the right to profit from other's work, and who has responsibility for guaranteeing or regulating access to valuable information. The pace of technological change is at once blinding and stubbornly inadequate. Preservation of digital information is not so much about protecting physical objects as about specifying the creation and maintenance of intangible electronic files whose intellectual integrity is their primary characteristic.
Preservation in the digital world is not exclusively a matter of longevity of optical disks, magnetic tape, and newer, more fragile storage media. The viability of digitized files is much more dependent on the life expectancy of the access systema chain is only as b as its weakest component. Today's digital media should be handled with care, but most likely will far outlast the capability of systems to retrieve and interpret the data stored on them. We can never know for certain when a system has become obsolete. Archives must prepare to migrate valuable digitized data, indexes, and software from one generation of computer technology to a subsequent generation. The use of digital technologies from a preservation perspective requires a deep and long standing institutional commitment to long-term access, the full integration of the technology into information management procedures and processes, and significant leadership in developing appropriate definitions and standards for digital preservation.
Selection for preservation in digital form is not a one-time choice made near the end of an item's life, but rather an ongoing process intimately connected to the active use of the digital files. An evaluation of the archival value of a record series, a manuscript collection, or a group of photographs in their original format is the necessary point of departure for the preservation of the digital version. The archival perspective first requires a commitment to preserving the integrity of a group of records as well as their contextual metadata. The archival value of these materials focuses on their value as evidence, not just as carriers of information. An assessment of the need for networked or rapid access, the protection of fragile originals, of the prevention of degradation from multi-generational copying must also be considered in the decision to convert documents from paper, film or analog media to digital form. The mere potential for increased access to a digitized collection does not add value to an underutilized collection. It is a rare collection of digital files indeed that can justify the cost of a comprehensive migration strategy without factoring in the larger intellectual context of related digital files stored elsewhere and their combined uses for research and scholarship.
Quality in the digital world is conditioned by the limitations of capture and display technology. Digital conversion places less emphasis on obtaining a faithful reproduction of the original than on finding the best representation of the original in digital form. Mechanisms and techniques for judging quality of digital reproductions are different and more sophisticated than those for assessing microfilm or photocopy reproductions. The primary goal of preservation quality is to capture as much intellectual and visual or aural content as is technically possible and then display that content to users in ways most appropriate to their needs.
In the digital world, a commitment to the integrity of a digital file begins with limiting the loss of information that occurs when a file is created originally and then compressed mathematically for storage or transmission across a network. Structural indexes and data descriptions of materials prepared as discrete finding aids or bibliographic records must be preservedas Metadataalong with the digital files themselves. The preservation of intellectual integrity also involves authentication procedures, like audit trails, to make sure files are not altered intentionally or accidentally.
In the digital world access is the central distinguishing quality of preservation. Digital technology is more than another way to copy a deteriorating document. Imaging involves transforming the very concept of format, not simply creating an accurate picture of a document, photograph, or map on a different medium. Preservation in the digital world is the act of ensuring continuing access to a high-quality, high-value, well-protected, and fully-integrated version of an original source document. Responsibility for long-term access to digital archives rests initially with the creator or owner of the materials. The resource and administrative implications of this fact cannot be minimized and must play a role in the decision to digitize archival and manuscript materials.
We know that the impulse to record and keep is part of our human nature. Like the clerks and scribes who went before them, archivists increase the chances that evidence about how we live, how we think, and what we have done will be preserved. It has long been the responsibility of archivists to assemble, organize, and protect this evidence. Long-term preservation of information in digital form encompasses the initial choice of a technology, the use of digital technologies for reproducing historically valuable materials, and the protection of the resulting digital information itself for as long as that information has value to an institution and clients it serves.
Preservation of Digitized ReproductionsSelected Readings
Conway, Paul. Preservation in the Digital World. Washington, D.C.: Commission on Preservation and Access, March 1996.
Hedstrom, Margaret. Understanding Electronic Incunabula: A Framework for Research on Electronic Records. American Archivist 54 (Fall 1991): 334-54.
Kenney, Anne R. and Stephen Chapman. Digital Resolution Requirements for Replacing Text-based Material: Methods for Benchmarking Image Quality. Washington, D.C.: Commission on Preservation and Access, 1995.
Lynch, Clifford. The Integrity of Digital Information: Mechanics and Definitional Issues. Journal of the American Society for Information Science 45 (December 1994): 737-44.
Preservation of Digital Information: Report of the Task Force on Archiving of Digital Information. Washington, D.C.: Research Libraries Group and Commission on Preservation and Access, May 1996.