File that represents the best copy produced by a digitizing organization, with best defined as meeting the objectives of a particular project or program. These objectives differ from one content category to another and the specifications to be recommended at this Web site (forthcoming) will be tailored to fit a variety of common categories and objectives. In some cases, an archive may produce more than one archival master file.
The terms used to name types of files vary within the digital library and digital archiving communities. In many cases, the best copies are called preservation master files rather than archival master files. In some cases, best-copy files are defined in qualitative terms, as part of an approach that requires all archival or preservation master files to meet the same specifications, without regard to objectives that vary by category.
Archival master files represent digital content that the organization intends to maintain for the long term without loss of essential features. For analog originals, archival master files are produced by reformatting to high standards. Practices vary from archive to archive regarding adjusting or cleaning up the content in the file. (This refers to adjustments like changing image tonality or reducing the audibility of clicks and pops in sound recordings.) Some archives may make such adjustments in real time when digitizing, but most apply such changes later in the workflow when production master files are created.
The digital formats for archival master files are selected in terms of sustainability factors. For born digital originals, if the existing format is deemed sustainable for the long term, the files are retained as-is and called archival masters. If the existing format is deemed unsuitable for long-term retention, e.g., it is an obsolescent format, then the content may be transcoded and the new version retained as the archival master. (If there is risk of data loss from the transcoding, files in the existing format may also be retained for possible future reference.)
Archival master files are the starting point when organizations produce the production master files and/or derivative files that will in turn support a wide range of objectives, e.g., the provision of end-user access; high quality reproduction; and the production of textual representations from OCR, voice recognition, or other similar process. It is again the case that practices vary, with some archives or projects seeing the creation of additional file types with nuanced differences in their characteristics. For example, according to the final report of the Sound Directions project, when the Indiana University team digitized analog sound recordings, they produced preservation master files, preservation master-intermediate files, and production master files, as well as derivative files (pp. 45 ff). A recent planning document from the National Archives and Records Administration notes that some projects will produce preservation master files, production/AV intermediate files, and reference files, in addition to derivative files.
Master files of all types have permanent value and should be managed in an appropriate environment, e.g., one in which read and write executions are minimized and other preservation-oriented data management actions are applied. In contrast, derivative files are frequently accessed by end-users and are typically stored in systems that see repeated read and write executions.