Bit Level Preservation and Long Term Usability
This guidance expresses to what extent the Library preserves all digital collections material and what factors impact future renderability of digital content.
The Library ensures bit-level preservation of all inventoried digital content in its permanent collections. Bit-level preservation provides the cornerstone of the Library’s digital preservation strategy and ensures the Library’s ability to provide current and future users with access to authentic and accurate copies of digital content. Maintaining the original bitstream allows for maximum variability for the future, since we do not know the full extent of future use and processing. Bit-level preservation alone, however, does not ensure that content is fully usable in the many ways that users may want to interact with it. For example, a bitstream in an unknown or obsolete format or encoding may not be possible to render as expected without legacy software or codecs, original software may not be available or may be unusable due to licensing restrictions, or other derived representations may depend on obsolete or unavailable hardware.
The Library often takes other appropriate preservation and processing actions, which may modify the context and structure of digital content, to ensure that collections remain available for longterm access and use. For example, the Library’s Digital Content Managers may remove files during routine processing, make changes to honor donor agreements, or restrict personally identifiable information in digital collection materials. The Library strives to record all preservation actions through metadata logs or other documentation, which are maintained by appropriate custodial divisions.
The Library is dedicated to maximizing the usability potentials for content preserved at the bit level. The Library strives to serve digital collections materials to users in ways that preserve their content, structure, and functionality, and in many cases does this via transformation or access derivatives. The publication of the Recommended Formats Statement and Sustainability of Digital Formats, and the Library’s coordination of the Federal Agencies Digital Guidelines Initiative have helped the Library meet this goal by identifying preferred formats and specifications.