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Digital preservation

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Digital preservation can be understood as the series of managed activities necessary to ensure continued access to digital materials for as long as necessary.[1] It combines policies, strategies and actions to ensure access to reformatted and born digital content regardless of the challenges of media failure and technological change. The goal of digital preservation is the accurate rendering of authenticated content over time.[2]


Challenges of digital preservation

Society's heritage has been presented on many different materials, including stone, vellum, bamboo, silk, and paper. Now a large quantity of information exists in digital forms, including emails, blogs, social networking websites, national elections websites, web photo albums, and sites which change their content over time. With digital media it is easier to create content and keep it up-to-date, but at the same time there are many challenges in the preservation of this content, both technical and economic.

Unlike traditional analog objects such as books or photographs where the user has unmediated access to the content, a digital object always needs a software environment to render it. These environments keep evolving and changing at a rapid pace, threatening the continuity of access to the content.[3] Physical storage media, data formats, hardware, and software all become obsolete over time, posing significant threats to the survival of the content.[2] This process can be referred to as digital obsolescence.

In the case of born-digital content (e.g., institutional archives, Web sites, electronic audio and video content, born-digital photography and art, research data sets, observational data), the enormous and growing quantity of content presents significant scaling issues to digital preservation efforts.

Digital content can also present challenges to preservation because of its complex and dynamic nature, e.g., interactive Web pages, virtual reality and gaming environments, learning objects, social media sites.[4]

The economic challenges of digital preservation are also great. Preservation programs require significant up front investment to create, along with ongoing costs for data ingest, data management, data storage, and staffing. One of the key strategic challenges to such programs is the fact that, while they require significant current and ongoing funding, their benefits accrue largely to future generations.[5]

Intellectual foundations of digital preservation

"Preserving Digital Information (1996)"

The challenges of long-term preservation of digital information have been recognized by the archival community for years.[6] In December 1994, the Research Libraries Group (RLG) and Commission on Preservation and Access (CPA) formed a Task Force on Archiving of Digital Information with the main purpose of investigating what needed to be done to ensure long-term preservation and continued access to the digital records. The final report published by the Task Force (Garrett, J. and Waters, D., ed. (1996). “Preserving digital information: Report of the task force on archiving of digital information.”[7]) became a fundamental document in the field of digital preservation that helped set out key concepts, requirements, and challenges.[6][8]

The Task Force proposed development of a national system of digital archives that would take responsibility for long-term storage and access to digital information; introduced the concept of trusted digital repositories and defined their roles and responsibilities; identified five features of digital information integrity (content, fixity, reference, provenance, and context) that were subsequently incorporated into a definition of Preservation Description Information in the Open Archival Information System Reference Model; and defined migration as a crucial function of digital archives. The concepts and recommendations outlined in the report laid a foundation for subsequent research and digital preservation initiatives.[9][10]

OAIS

To standardize digital preservation practice and provide a set of recommendations for preservation program implementation, the Reference Model for an Open Archival Information System (OAIS) was developed. OAIS is concerned with all technical aspects of a digital object’s life cycle: ingest into and storage in a preservation infrastructure, data management, accessibility, and distribution. The model also addresses metadata issues and recommends that five types of metadata be attached to a digital object: reference (identification) information, provenance (including preservation history), context, fixity (authenticity indicators), and representation (formatting, file structure, and what "imparts meaning to an object’s bitstream").[11]

Trusted Digital Repository Model

In March 2000, the Research Libraries Group (RLG) and Online Computer Library Center (OCLC) began a collaboration to establish attributes of a digital repository for research organizations, building on and incorporating the emerging international standard of the Reference Model for an Open Archival Information System (OAIS). In 2002, they published “Trusted Digital Repositories: Attributes and Responsibilities.” In that document a “Trusted Digital Repository” (TDR) is defined as "one whose mission is to provide reliable, long-term access to managed digital resources to its designated community, now and in the future." The TDR must include the following seven attributes: compliance with the reference model for an Open Archival Information System (OAIS), administrative responsibility, organizational viability, financial sustainability, technological and procedural suitability, system security, procedural accountability. The Trusted Digital Repository Model outlines relationships among these attributes. The report also recommended the collaborative development of digital repository certifications, models for cooperative networks, and sharing of research and information on digital preservation with regard to intellectual property rights.[12]

In 2004 Henry M. Gladney proposed another approach to digital object preservation that called for the creation of “Trustworthy Digital Objects” (TDOs). TDOs are digital objects that can speak to their own authenticity since they incorporate a record maintaining their use and change history, which allows the future users to verify that the contents of the object are valid.[13]

InterPARES

InterPARES (International Research on Permanent Authentic Records in Electronic Systems) is a collaborative research initiative led by the University of British Columbia that is focused on addressing issues of long-term preservation of authentic digital records. The research is being conducted by focus groups from various institutions in North America, Europe, Asia, and Australia, with an objective of developing theories and methodologies that provide the basis for strategies, standards, policies, and procedures necessary to ensure the trustworthiness, reliability, and accuracy of digital records over time.[14]

The project began in 1999 with the first phase, InterPARES 1, which ran to 2001 and focused on establishing requirements for authenticity of inactive records generated and maintained in large databases and document management systems created by government agencies.[15] InterPARES 2 (2002 – 2007) concentrated on issues of reliability, accuracy and authenticity of records throughout their whole lifecycle, and examined records produced in dynamic environments in the course of artistic, scientific and online government activities.[16] The third five-year phase (InterPARES 3) was initiated in 2007. Its goal is to utilize theoretical and methodological knowledge generated by InterPARES and other preservation research projects for developing guidelines, action plans, and training programs on long-term preservation of authentic records for small and medium-sized archival organizations.[17]

Strategies

In 2006, the Online Computer Library Center developed a four-point strategy for the long-term preservation of digital objects that consisted of:

  • Assessing the risks for loss of content posed by technology variables such as commonly used proprietary file formats and software applications.
  • Evaluating the digital content objects to determine what type and degree of format conversion or other preservation actions should be applied.
  • Determining the appropriate metadata needed for each object type and how it is associated with the objects.
  • Providing access to the content.[18]

There are several additional strategies that individuals and organizations may use to actively combat the loss of digital information.

Refreshing

Refreshing is the transfer of data between two types of the same storage medium so there are no bitrot changes or alteration of data.[11] For example, transferring census data from an old preservation CD to a new one. This strategy may need to be combined with migration when the software or hardware required to read the data is no longer available or is unable to understand the format of the data. Refreshing will likely always be necessary due to the deterioration of physical media.

Migration

Migration is the transferring of data to newer system environments (Garrett et al., 1996). This may include conversion of resources from one file format to another (e.g., conversion of Microsoft Word to PDF or OpenDocument), from one operating system to another (e.g., Windows to GNU/Linux) or from one programming language to another (e.g., C to Java) so the resource remains fully accessible and functional. Resources that are migrated run the risk of losing some type of functionality since newer formats may be incapable of capturing all the functionality of the original format, or the converter itself may be unable to interpret all the nuances of the original format. The latter is often a concern with proprietary data formats.

Replication

Creating duplicate copies of data on one or more systems is called replication. Data that exists as a single copy in only one location is highly vulnerable to software or hardware failure, intentional or accidental alteration, and environmental catastrophes like fire, flooding, etc. Digital data is more likely to survive if it is replicated in several locations. Replicated data may introduce difficulties in refreshing, migration, versioning, and access control since the data is located in multiple places.

Emulation

Emulation is the replicating of functionality of an obsolete system.[19] Examples include emulating an Atari 2600 on a Windows system or emulating WordPerfect 1.0 on a Macintosh. Emulators may be built for applications, operating systems, or hardware platforms. Emulation has been a popular strategy for retaining the functionality of old video game systems, such as with the MAME project. The feasibility of emulation as a catch-all solution has been debated in the academic community. (Granger, 2000)

Raymond A. Lorie has suggested a Universal Virtual Computer (UVC) could be used to run any software in the future on a yet unknown platform.[20] The UVC strategy uses a combination of emulation and migration. The UVC strategy has not yet been widely adopted by the digital preservation community.

Jeff Rothenberg, a major proponent of Emulation for digital preservation in libraries, working in partnership with Koninklijke Bibliotheek and National Archief of the Netherlands, developed a software program called Dioscuri, a modular emulator that succeeds in running MS-DOS, WordPerfect 5.1, DOS games, and more.[21]

Metadata attachment

Metadata is data on a digital file that includes information on creation, access rights, restrictions, preservation history, and rights management.[22] Metadata attached to digital files may be affected by file format obsolescence. ASCII is considered to be the most durable format for metadata [23] because it is widespread, backwards compatible when used with Unicode, and utilizes human-readable characters, not numeric codes. It retains information, but not the structure information it is presented in. For higher functionality, SGML or XML should be used. Both markup languages are stored in ASCII format, but contain tags that denote structure and format.

Digital sustainability

Digital sustainability encompasses a range of issues and concerns that contribute to the longevity of digital information.[24] Unlike traditional, temporary strategies, and more permanent solutions, digital sustainability implies a more active and continuous process. Digital sustainability concentrates less on the solution and technology and more on building an infrastructure and approach that is flexible with an emphasis on interoperability, continued maintenance and continuous development.[25] Digital sustainability incorporates activities in the present that will facilitate access and availability in the future.[26][27]

Preservation repository assessment and certification

A few of the major frameworks for digital preservation repository assessment and certification are described below. A more detailed list is maintained by the U.S. Center for Research Libraries:[28]

Specific tools and methodologies

TRAC

In 2007, CRL/OCLC published Trustworthy Repositories Audit & Certification: Criteria & Checklist (TRAC), a document allowing digital repositories to assess their capability to reliably store, migrate, and provide access to digital content. TRAC is based upon existing standards and best practices for trustworthy digital repositories and incorporates a set of 84 audit and certification criteria arranged in three sections: Organizational Infrastructure; Digital Object Management; and Technologies, Technical Infrastructure, and Security.[29]

TRAC "provides tools for the audit, assessment, and potential certification of digital repositories, establishes the documentation requirements required for audit, delineates a process for certification, and establishes appropriate methodologies for determining the soundness and sustainability of digital repositories".[30]

DRAMBORA

DRAMBORA (Digital Repository Audit Method Based On Risk Assessment), introduced by the Digital Curation Centre (DCC) and Digital Preservation Europe (DPE) in 2007, offers a methodology and a toolkit for digital repository self-assessment.

The DRAMBORA process is arranged in six stages and concentrates on evaluation of likelihood and potential impact of risks on the repository. The auditor is required to describe and document the repository’s role, objectives, policies, activities and assets, in order to identify and assess the risks associated with these activities and assets and define appropriate measures to manage them.[31]

European Framework for Audit and Certification of Digital Repositories

The European Framework for Audit and Certification of Digital Repositories was defined in a memorandum of understanding signed in July 2010 between CCSDS (Consultative Committee for Space Data Systems), DSA (Data Seal of Approval) Board and DIN (German Institute for Standardization) "Trustworthy Archives – Certification" Working Group.

The framework is intended to help organizations in obtaining appropriate certification as a trusted digital repository and establishes three increasingly demanding levels of assessment:

  1. Basic Certification: self-assessment using 16 criteria of the Data Seal of Approval (DSA).
  2. Extended Certification: Basic Certification and additional externally reviewed self-audit against ISO 16363 or DIN 31644 requirements.
  3. Formal Certification: validation of the self-certification with a third-party official audit based on ISO 16363 or DIN 31644.[32]

nestor Catalogue of Criteria

A German initiative, nestor (the Network of Expertise in Long-Term Storage of Digital Resources) sponsored by the German Ministry of Education and Research, developed a catalogue of criteria for trusted digital repositories in 2004. In 2008 the second version of the document was published. The catalogue, aiming primarily at German cultural heritage and higher education institutions, establishes guidelines for planning, implementing, and self-evaluation of trustworthy long-term digital repositories.[33]

The nestor catalogue of criteria conforms to the OAIS reference model terminology and consists of three sections covering topics related to Organizational Framework, Object Management, and Infrastructure and Security.[34]

PLATTER

PLATTER (Planning Tool for Trusted Electronic Repositories) is a tool released by DigitalPreservationEurope (DPE) to help digital repositories in identifying their self-defined goals and priorities in order to gain trust from the stakeholders.[35]

PLATTER is intended to be used as a complementary tool to DRAMBORA, NESTOR, and TRAC. It is based on ten core principles for trusted repositories and defines nine Strategic Objective Plans, covering such areas as acquisition, preservation and dissemination of content, finance, staffing, succession planning, technical infrastructure, data and metadata specifications, and disaster planning. The tool enables repositories to develop and maintain documentation required for an audit.[31]: 49 

Audit and Certification of Trustworthy Digital Repositories (ISO 16363)

Audit and Certification of Trustworthy Digital Repositories (ISO 16363:2012), developed by the Consultative Committee for Space Data Systems (CCSDS), was approved as a full international standard in March 2012. Extending the OAIS Reference Model and based largely on the TRAC checklist, the standard is designed for all types of digital repositories. It provides a detailed specification of criteria against which the trustworthiness of a digital repository should be evaluated.[36]

The CCSDS Repository Audit and Certification Working Group has also developed and submitted for approval a second standard, Requirements for Bodies Providing Audit and Certification of Candidate Trustworthy Digital Repositories (ISO 16919), that defines the external auditing process and requirements for organizations responsible for assessment and certification of digital repositories.[37]

Digital preservation best practices

Although preservation strategies vary for different types of materials and between institutions, adhering to nationally and internationally recognized standards and practices is a crucial part of digital preservation activities. Best or recommended practices define strategies and procedures that may help organizations to implement existing standards or provide guidance in areas where no formal standards have been developed.[38]

Best practices in digital preservation continue to evolve and may encompass processes that are performed on content prior to or at the point of ingest into a digital repository as well as processes performed on preserved files post-ingest over time. Best practices may also apply to the process of digitizing analog material and may include the creation of specialized metadata (such as technical, administrative and rights metadata) in addition to standard descriptive metadata. The preservation of born-digital content may include format transformations to facilitate long-term preservation or to provide better access.[39]

Audio preservation

Various best practices and guidelines for digital audio preservation have been developed, including:

  • Capturing Analog Sound for Digital Preservation: Report of a Roundtable Discussion of Best Practices for Transferring Analog Discs and Tapes (2006)[40], which defined procedures for reformatting sound from analog to digital and provided recommendations for best practices for digital preservation
  • Digital Audio Best Practices (2006) prepared by the Collaborative Digitization Program Digital Audio Working Group, which provides guidelines and a set of best practices for cultural heritage institutions interested in converting analog audio recordings to digital formats[41]
  • Sound Directions: Best Practices for Audio Preservation (2007) published by the Sound Directions Project[38] , which describes the audio preservation workflows and recommended best practices and has been used as the basis for other projects and initiatives[42], [43]
  • Documents developed by the International Association of Sound and Audiovisual Archives (IASA), the European Broadcasting Union (EBU), the Library of Congress, and the Digital Library Federation (DLF).

The Audio Engineering Society (AES) also issues a variety of standards and guidelines relating to the creation of archival audio content and technical metadata.[44]

Examples of digital preservation initiatives

Further information: List of digital preservation initiatives
Digitization at the British Library of a Dunhuang manuscript for the International Dunhuang Project


A number of open source products have been developed to assist with digital preservation, including DSpace, Fedora, EPrints and Research-Output Repository Platform. The commercial sector also offers digital preservation software tools, such as Ex Libris Ltd.'s Rosetta, Tessella Ltd.'s Safety Deposit Box, CONTENTdm, Digital Commons, Equella, intraLibrary, Open Repository and Vital.[45]

Large-scale digital preservation initiatives (LSDIs)

Many research libraries and archives have begun or are about to begin Large-Scale digital preservation initiatives (LSDIs). The main players in LSDIs are cultural institutions, commercial companies such as Google and Microsoft, and non-profit groups including the Open Content Alliance (OCA), the Million Book Project (MBP), and HathiTrust. The primary motivation of these groups is to expand access to scholarly resources.

LSDIs: library perspective

Approximately 30 cultural entities, including the 12-member Committee on Institutional Cooperation (CIC), have signed digitization agreements with either Google or Microsoft. Several of these cultural entities are participating in the Open Content Alliance (OCA) and the Million Book Project (MBP). Some libraries are involved in only one initiative and others have diversified their digitization strategies through participation in multiple initiatives. The three main reasons for library participation in LSDIs are: Access, Preservation and Research and Development. It is hoped that digital preservation will ensure that library materials remain accessible for future generations. Libraries have a perpetual responsibility for their materials and a commitment to archive their digital materials. Libraries plan to use digitized copies as backups for works in case they go out of print, deteriorate, or are lost and damaged.

See also

Footnotes

  1. ^ Digital Preservation Coalition (2008). "Introduction: Definitions and Concepts". Digital Preservation Handbook. York, UK. Retrieved 24 February 2012.
  2. ^ a b Evans, Mark; Carter, Laura. (December 2008). The Challenges of Digital Preservation. Presentation at the Library of Parliament, Ottawa.
  3. ^ Becker,C.; et al. (2009). "Systematic planning for digital preservation". International Journal on Digital Libraries (10): pp.133–157. doi:10.1007/s00799-009-0057-1. {{cite journal}}: |pages= has extra text (help); Explicit use of et al. in: |last= (help)
  4. ^ Arora, Jagdish (2009). "Digital Preservation, an Overview.". Proceedings of the National Seminar on Open Access to Textual and Multimedia Content: Bridging the Digital Divide, January 29-30, 2009. p. 111. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)CS1 maint: date and year (link)
  5. ^ Blue Ribbon Task Force on Sustainable Digital Preservation and Access (2010). "Sustainable Economics for a Digital Planet: Ensuring Long-Term Access to Digital Information, final report" (PDF). La Jolla, Calif. p. 35. Retrieved July 5, 2012.
  6. ^ a b Tibbo, Helen R. (2003). "On the Nature and Importance of Archiving in the Digital Age". Advances in Computers. 57: p.26. doi:10.1016/S0065-2458(03)57001-2. {{cite journal}}: |pages= has extra text (help)
  7. ^ Donald Waters (1996). Preserving digital information: Report of the task force on archiving of digital information. CLIR. ISBN 1-88733450-5. Retrieved November 15, 2012. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  8. ^ Inter-university Consortium for Political and Social Research (ICPSR) (2009). "Principles and Good Practice for Preserving Data". International Household Survey Network, IHSN Working Paper No 003. pp. 5–6. Retrieved September 17, 2012.
  9. ^ Harvey, Ross (2012). Preserving Digital Materials. Berlin, K. G. Saur. pp. 97, 156. ISBN 9783110253689.
  10. ^ Conway, Paul (2010). "Preservation in the Age of Google: Digitization, Digital Preservation, and Dilemmas". The Library Quarterly. 80 (1): pp.66-67. Retrieved September 17, 2012. {{cite journal}}: |pages= has extra text (help)
  11. ^ a b Cornell University Library. (2005) Digital Preservation Management: Implementing Short-term Strategies for Long-term Problems
  12. ^ Research Libraries Group. (2002). Trusted Digital Repositories: Attributes and Responsibilities
  13. ^ Gladney, H. M. (2004). "Trustworthy 100-year digital objects: Evidence after every witness is dead". ACM Transactions on Information Systems. 22 (3): 406–436. doi:10.1145/1010614.1010617.
  14. ^ Suderman, Jim (2010). "Principle-based concepts for the long-term preservation of digital records". Proceedings of the 1st International Digital Preservation Interoperability Framework Symposium: Article No. 7. doi:10.1145/2039263.2039270.
  15. ^ Duranti, Luciana (2001). "The Long-Term Preservation of Authentic Electronic Record" (PDF). Proceedings of the 27th VLDB Conference, Roma, Italy. Retrieved September 21, 2012.
  16. ^ Hackett, Yvette (2003). "InterPARES: The Search for Authenticity in Electronic Records". The Moving Image. 3 (2): p.106. {{cite journal}}: |pages= has extra text (help)
  17. ^ Laszlo, Krisztina (2008). "The InterPARES 3 Project: Implementing Digital Records Preservation in a Contemporary Art Gallery and Ethnographic Museum" (PDF). Annual conference of the International Documentation Committee of the International Council of Museums (CIDOC), 15-18 September 2008, Athens, Greece: p.4. Retrieved September 21, 2012. {{cite journal}}: |pages= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  18. ^ Online Computer Library Center, Inc. (2006). OCLC Digital Archive Preservation Policy and Supporting Documentation, p. 5
  19. ^ Rothenberg, Jeff (1998). Avoiding Technological Quicksand: Finding a Viable Technical Foundation for Digital Preservation. Washington, DC, USA: Council on Library and Information Resources. ISBN 1-887334-63-7.
  20. ^ Lorie, Raymond A. (2001). "Long Term Preservation of Digital Information". Proceedings of the 1st ACM/IEEE-CS Joint Conference on Digital Libraries (JCDL '01). Roanoke, Virginia, USA. pp. 346–352. {{cite conference}}: External link in |title= (help); Unknown parameter |booktitle= ignored (|book-title= suggested) (help)
  21. ^ Hoeven, J. (2007). "Dioscuri: emulator for digital preservation". D-Lib Magazine. 13 (11/12). doi:10.1045/november2007-inbrief.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  22. ^ NISO Framework Advisory Group. (2007). A Framework of Guidance for Building Good Digital Collections, 3rd edition, p. 57,
  23. ^ National Initiative for a Networked Cultural Heritage. (2002). NINCH Guide to Good Practice in the Digital Representation and Management of Cultural Heritage Materials
  24. ^ Bradley, K. (Summer 2007). Defining digital sustainability. Library Trends v. 56 no 1 p. 148-163.
  25. ^ Sustainability of Digital Resources. (2008). TASI: Technical Advisory Service for Images.
  26. ^ Towards a Theory of Digital Preservation. (2008). International Journal of Digital Curation
  27. ^ Electronic Archives Preservation Policy
  28. ^ "Center for Research Libraries - Other Assessment Tools". Retrieved Sept. 6, 2012. {{cite web}}: Check date values in: |accessdate= (help)
  29. ^ OCLC and CRL (2007). "Trustworthy Repository Audit & Certification: Criteria & Checklist" (PDF). Retrieved April 16, 2012.
  30. ^ Phillips, Stephen C (2010). "Service level agreements for storage and preservation, p.13". Retrieved May 1, 2012.
  31. ^ a b Ball, Alex (2010). "Preservation and Curation in Institutional Repositories (version 1.3)" (PDF). Edinburgh, UK: Digital Curation Centre. p. 48. Retrieved June 24, 2012.
  32. ^ APARSEN Project (2012). "Report on Peer Review of Digital Repositories" (PDF): 10. Retrieved October 8, 2012. {{cite journal}}: Cite journal requires |journal= (help)
  33. ^ Dobratz, Susanne (2007). "Trustworthy Digital Long-Term Repositories: The Nestor Approach in the Context of International Developments". Research and Advanced Technology for Digital Libraries. Springer Berlin / Heidelberg. pp. 210–222. ISBN 978-3-540-74850-2. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  34. ^ Horstkemper, Gregor (2009). "Assessment of Trustworthiness of Digital Archives" (PDF). Proceedings of the Sino-German Symposium on Development of Library and Information Services. pp. 74–75. Retrieved October 2, 2012. {{cite web}}: More than one of |author= and |last= specified (help)
  35. ^ DigitalPreservationEurope (2008). "DPE Repository Planning Checklist and Guidance DPED3.2" (PDF). Retrieved June 24,2012. {{cite web}}: Check date values in: |accessdate= (help)
  36. ^ CCSDS (2011). "Audit and Certification of Trustworthy Digital Repositories, Recommended Practice" (PDF). CCSDS 652.1-M-1. Issue 1. Washington, DC: CCSDS, September 2011. p. 1-1. Retrieved October 10, 2012.
  37. ^ Ruusalepp, Raivo (2012). "Standards Alignment". In McGovern, Nancy Y (ed.). Aligning National Approaches to Digital Preservation. Atlanta, GA: Educopia Institute. p. 124. ISBN 978-0-9826653-1-2. {{cite book}}: More than one of |pages= and |page= specified (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  38. ^ a b Casey, M. (2007). "Sound Directions: Best Practices for Audio Preservation" (PDF). Bloomington: Indiana University and Cambridge: Harvard University. Retrieved 30 October, 2012. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  39. ^ Verheul, I. (2006). "Networking for Digital Preservation: Current Practice in 15 National Libraries" (PDF). K.G. Saur, Munich. Retrieved 30 October, 2012. {{cite web}}: Check date values in: |accessdate= (help)
  40. ^ Council on Library and Information Resources (2006). "Publication 137: Capturing Analog Sound for Digital Preservation: Report of a Roundtable Discussion of Best Practices for Transferring Analog Discs and Tapes". Retrieved 6 September, 2012. {{cite web}}: Check date values in: |accessdate= (help)
  41. ^ Digital Audio Working Group. Collaborative Digitization Program (2006). "Digital Audio Best Practices (Version 2.1)" (PDF). Aurora, Colorado. Retrieved 30 October, 2012. {{cite journal}}: Check date values in: |accessdate= (help); Cite journal requires |journal= (help)
  42. ^ Columbia University Libraries (2010). "Preserving Historic Audio Content: Developing Infrastructures and Practices for Digital Conversion. Final Report to the Andrew W. Mellon Foundation" (PDF). p. 5. Retrieved 30 October, 2012. {{cite web}}: Check date values in: |accessdate= (help)
  43. ^ Beers, Shane (2011). "Hathi Trust and the Challenge of Digital Audio" (PDF). IASA Journal (36): p.39. Retrieved 5 November, 2012. {{cite journal}}: |page= has extra text (help); Check date values in: |accessdate= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  44. ^ Audio Engineering Society. "Publications". Retrieved 5 November, 2012. {{cite web}}: Check date values in: |accessdate= (help)
  45. ^ Fojtu, Andrea (2009). "Open Source versus Commercial Solutions for a Long-term Preservation in Digital Repositories" (PDF). CASLIN 2009. Institutional Online Repositories and Open Access. University of West Bohemia. p. 79-80. Retrieved 25 October 2012.

References

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