Digital Preservation encompasses a broad range of activities designed to extend the usable life of machine-readable computer files and protect them from media failure, physical loss, and obsolescence. TDR divides digital preservation activities into those that promote the long-term maintenance of a bitstream (the zeros and ones) and those that provide continued accessibility of its contents. The OCLC/RLG Working Group on Preservation Metadata's report, Preservation Metadata and the OAIS Information Model, added the concept of viability to the maintenance of the bitstream, indicating that information must be intact and readable from the storage media, and further subdivides the content accessibility need into renderability (viewable by humans and processible by computers) and understandability (interpretable by humans). As these terms imply, it is one thing to preserve a bitstream, but quite another to preserve the content, form, style, appearance, and functionality. We conceive of digital preservation as a process that requires the use of the best available technology as well as carefully thought out administrative policies and procedures.
See Strategies, later in this section, for a further discussion of digital preservation strategies.