Principles and Specifications
Library of Congress preservation specifications for digital capture; structural, administrative, and descriptive metadata; and delivery are based on current standards and best practices in the Preservation community, LC experience through the National Digital Library Program (NDLP), and new approaches developed by the LC Preservation Directorate.
Underlying Principles
- Retain an analog version of digitally-reformatted items until the Preservation Directorate has confidence that the life-cycle management of digital data will ensure access for as long as, or longer than, the analog version. The analog version may be the original item, paper facsimile, or microfilm copy, and may be restricted for use after the digital reproduction is available.
- Ensure the appropriate handling and treatment of originals, and work with curators, recommending officers, and other Preservation staff to make decisions about disbinding, housing, and related matters.
- Minimize handling of originals in the digital reformatting work to assure the best digital capture of an undamaged original, as well as the longevity of the original item, especially if it is to serve as the analog version.
- Ensure that the digital master file will allow a broad range of future use, including planned phases of delivery, by employing appropriate standards and best practices.
- Capture the highest quality digital image technically possible and economically feasible for large-scale production, while optimizing the potential for longevity.
- Archive a digital master file that is free of, or minimizes, artifacts introduced by the reformatting process, whenever possible.
- Ensure the completeness of all materials being digitally reformatted to a standard comparable to that employed for preservation microfilm.
- Optimize digital images of paper-based text materials for use in creating a new paper facsimile, when appropriate.
- Employ economical, automated methods to create machine-readable text with minimal encoding (such as that recommended by the TEI in Libraries Guidelines to provide access with searchable text and allow for future expanded use and encoding, when appropriate.
- Employ standards and best practices for structural, administrative, and descriptive metadata that will optimize interoperability with LC, national, and international digital library efforts, and facilitate the life-cycle management of the digital objects.
- Document digital master file contents with MD5 checksums (or a similar tool) and use them to ensure the data integrity of master files through back-up and migration.
