The
Preservation of Digitized Reproductions
Preamble
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
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 system -- a chain is only as strong 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
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
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.
Integrity
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 preserved
-- as Metadata -- along with the digital files themselves. The perservation
of intellectual integrity also involves authentication procedures, like
audit trails, to make sure files are not altered intentionally or accidentally.
Access
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.
Approved
by the Society of American Archivists Council
June 9, 1997
PRESERVATION
OF DIGITIZED REPRODUCTIONS
Selected
Readings
Besser,
Howard and Jennifer Trant, Introduction to Imaging: Issues in Constructing
an Image Database. Santa Monica: Getty Art History Information Program,
1995.
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.
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