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E2401e – NDL Develops Basic Plan for Long-Term Preservation of Digital Materials 2021-2025

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Current Awareness-E No.416

8 July, 2021

NDL Develops Basic Plan for Long-Term Preservation of Digital Materials 2021-2025


In March 2021, the National Diet Library (NDL) developed “National Diet Library Basic Plan for Long-term Preservation of Digital Materials 2021-2025” (hereafter the “Basic Plan”). This article provides an overview of the Basic Plan, summarizing issues on long-term preservation of digital materials and reviewing related efforts made by the NDL to date.

●Issues Related to Long-term Preservation of Digital Materials

Digital materials at the NDL include digitized materials (materials digitally photographed from paper books and others) and Internet materials such as websites. However, preservation of packaged electronic publications such as CDs and DVDs are one of the most urgent issues in long-term preservation, to ensure future access to the nation’s cultural assets and intellectual resources. As follows, packaged electronic publications have several issues that are commonly found in digital materials.

  • Vulnerability of media
  • In general, the lifespan of media used to store digital materials is significantly shorter than that of paper materials. Some media, such as USB flash drives and rewritable (RW) optical discs, require careful management to prevent careless modification or deletion of data. A common measure for long-term preservation of digital materials is “migration (media conversion)” where data is transferred to media with longer lifespan. This is an effective countermeasure against vulnerability of media.
  • Difficulty of maintaining technical environment for use
  • In order to use digital materials, it is essential to maintain technical environment for use. However, every playback equipment has its own lifespan. Furthermore, to ensure data readability, obsolescence of not only hardware but also OS and playback software is an issue. In some cases, this can be solved by “emulation” technology, which reproduces the past environment on current PC environment. In other cases, the issue can be solved by “migration (format conversion)” which converts the files in a medium to another format that can be used for a longer period of time.

●Main Initiatives of the NDL to date

  • Checking the condition and investigating state of deterioration of optical discs
  • From FY2018 to FY2019, we conducted a sample survey on the state of deterioration of CDs and DVDs among packaged electronic publications collected and preserved at the NDL. The percentage of error values exceeding the criteria was larger for write-once (R) and rewritable (RW) materials than for read-only (ROM) materials.
  • A similar sample survey was conducted on BD-Rs for long-term preservation. We use them mainly for storing data for preservation of digitized materials and have a vast number of them. Some were found to have error values exceeding the criteria.
  • Trial of migration (media conversion)
  • From FY2018 to FY2020, we conducted a series of trials of migration (media conversion) of packaged electronic publications. The target media was selected in consideration of lifespan of the media, condition of playback devices, and risk of data deletion by possible accidental operation. In principle, DVD-R for long-term storage was used as destination medium after migration.
  • Most materials on USB flash drives, MO disks, and rewritable optical discs were accessible and readable for use by simply copying the data. Based on the work, we put together an in-house manual for migration. For floppy disks (FD), migration was carried out in a special format, saving data of a whole disk in a single file. In the end, we were able to identify issues such as methods to provide data after migration and improvement of migration environment for FDs that cannot be read in the current environment.
  • Technical research and study
  • We conducted a technical survey on construction of permanent preservation infrastructure (FY2016, see E1933) and an investigation on overall efforts for long-term preservation including questionnaires to overseas institutions (FY2019). Furthermore, as investigations related to measures for packaged electronic publications, we conducted a survey on migration methods (FY2017, see E2058) and a survey on the state of media deterioration (FY2018 and FY2019). All reports are available on the NDL website.

●Outline of the Basic Plan

Based on the above efforts, the Basic Plan continues to focus on implementation of preservation measures for packaged electronic publications. Among the changes from the previous plan, below are items with special emphasis (in parentheses are corresponding locations in the Basic Plan).

  • Inspection of the condition of materials in the collections (6(1)) and improvement to create a cost-effective preservation environment (6(5))
  • As mentioned above, investigation on the state of deterioration of optical discs is an important issue. We will continue to study inspection methods and to improve the system. In addition, we will consider adopting a more cost-effective preservation media and data transfer given the difficulty of managing vast number of BD-Rs that store data for preservation of digitized materials.
  • Maintaining technical environment for use (6(6)) and improving usage environment (6(7))
  • For the purpose of ensuring long-term use, conditions of playback devices will be checked regularly. Furthermore, environment for using and providing data after migration or the other preservation measures will be improved. We will also consider adopting technologies including emulation. Where necessary, we will collect old OS and replay software.
  • Technical research and study (7)
  • We will continue to research on matters that contribute to promotion of specific preservation measures. Such includes characterization and evaluation of storage media adaptable to data for preservation of digitized materials, more cost-effective migration methods, and technologies for ensuring long-term use.

●Future Developments

Digital materials have progressed and changed more rapidly than paper materials. As a result, existing media, file formats, and standards quickly become obsolete. While the Basic Plan covers the period up to the end of FY2025, NDL will pay attention to the latest technological trends and endeavor to preserve materials for a longer period of time with greater convenience for use.

Written by Kinoshita Takafumi
Digital Information Department
Digital Information Planning Division
Research and Development for Next-Generation Systems Office
Translated by Okada Aya

*Notes are not being translated and remain in Japanese language.

国立国会図書館. 国立国会図書館デジタル資料長期保存基本計画 2021-2025. 2021-03-03.
“電子情報の長期利用保証に関する調査研究”. 国立国会図書館.
里見航. NDL,2016年度電子情報の長期保存対策調査の概要報告書を公開. カレントアウェアネス-E. 2017, (328), E1933.
里見航. NDL,2017年度電子情報の長期保存対策調査の概要報告書を公開. カレントアウェアネス-E. 2018, (354), E2058.