Digital preservation - from theory to practice?
Keywords: digital preservation, OAIS, migration, digital data, culture heritage institutions
Mgr. Jan Hutař Ph.D., Archives New Zealand,10 Mulgrave Street, Thorndon, Wellington 6011, New Zealand / Mgr. Marek Melichar, Charles University in Prague, Computer Science Centre, Ovocný trh 3/5, 116 43 Praha 1, Czech Republic
This article was created in the project 516R1/2014 ”Pilot project for low barrier approach to digital preservation (LTP Pilot)” financed from the Cesnet Development Fund.
1 What is digital preservation
Our ability to understand information content coded in digital data depends not only on our knowledge, but also in large part, on the technologies we need to be able to find and use to access digital objects. The problem of obsolescence on a software and hardware level, the risk of loss of the context or loss of the ability to identify and find the objects together with overall fragility of the digital objects require our permanent attention. In recent years the amount of digital data created and shared in all areas of our everyday life grew dramatically. Some of this data (in reality only a fragment, as discussed in van der Werf, T., & van der Werf) should be preserved for future use. Permanent preservation of the digital information is very important when it comes to large data amounts resulting from several years of scientific research, years of scanning of physical documents in libraries or whenever the information stored in this data is critical for security, people’s health, or public administration.
We share large data amounts over networks, we know how to store it, but according the estimations only half of the digital information, which should be preserved, is treated properly with long-term preservation in mind. Physical preservation of the data in a technologically useable form may not be sufficient. Long-term preservation of the information content in digital form (LTP) must be systematic and practical activity with sole aim: to preserve the content coded in digital form in such a way that the archived information is usable and understandable to the future generations of users.
LTP is not some kind of conceptual game or philosophical discipline but purely the practical, everyday activity of many people in heritage institutions and companies. Its goals are to manage actively “digital content over time to ensure ongoing access.” Long-term digital preservation has also some collateral goals and unintended effects. It helps to develop collections, support the institutional missions, fulfill the legal obligations, protect the investment into the digital objects acquisition, and enforce institutional trustworthiness similar to the analogue world.
A lot of myths and misunderstandings inundate long-term digital preservation. They result from the complexity of the topic and ambiguities of the terminology and some of the conceptual models. Besides, not many institutions actually perform long-term preservation actions yet. LTP has reputation of a theoretical or conceptual discipline, activity which requires highly technical expertise. The decision to include the long-term preservation of digital information into institutional missions is often postponed. Initiatives supporting “personal digital archiving”, which publish methodologies and best practices, or organized conferences , are of great help in calling attention to this topic in a down to earth context, as are various other projects aimed at lowering the barriers to long-term digital preservation (projects like Preserving Digital Objects with Restricted Resources POWRR) or in the Czech context the recent project LTP Pilot. This project is mentioned later in this text in more detail.
Long-term preservation is not only about “keeping more copies in more places” or something we could start to care about any time later (Corrado, E. M., and H. L. Moulaison). Neither is it an effort that we could leave on the shoulders of the national or central institutions, where only huge projects with massive budgets make sense. Similarly, we do not need always exceptionally extensive technical expertise. Adrian Brown in his publication Practical digital preservation: a how-to guide for organizations of any size shows how even small institutions can kickoff projects aiming to secure long-term usability of their data.
2 Pragmatic approach to digital preservation
Long-term preservation of the information in digital form requires more than preservation of the 1s and 0s, the bit sequences. Bit stream preservation does not mitigate the impact of the software and hardware obsolescence or digital objects’ formats obsolescence; neither can it help to preserve the authenticity or usability of the intellectual content. Passive bit stream preservation is preconditioning or the first step to logical preservation. Logical preservation is active and systematically planned. It rests in activities performed during the whole lifecycle of the digital objects with the goal of preserving permanent usability of the information content. Usability is an umbrella concept encompassing the ability to find the objects, render them, understand them intellectually and assess their authenticity. To preserve permanent usability the documents in the archive have to be permanently “alive.” They must reflect the changes in the global technical environment, and react to changes required by object management. Besides the preserved objects themselves, accompanying metadata (describing the properties of the content, its context, archiving history), must be also preserved. This metadata should be perpetually updated. Each significant event or change of the archived objects should be retraceable in the metadata.
From a practical point of view, the long-term preservation short-term goal is to hand over the preserved data to the next generation of data curators with sufficient accompanying metadata: information about the data and actions and checks performed on the archived content in previous archiving periods. Permanent preservation of digital content requires pragmatic decisions about what events have to be recorded, what technical information should be extracted from the objects and its environment, in what format it should be stored, what contextual and representation information should be stored together with the preserved content and so on. Pragmatic approach to long-term digital preservation also means to embark with realistic expectations and a step-by-step approach to improving the solution. It is better not to expect a final solution immediately for everything and instead use partial solutions than do nothing. Project POWRR describes a pragmatic approach to digital preservation:
- inventory and analyze content to determine specific needs
- use simple processing tools to collect sufficient metadata
- explore robust technical solutions with the understanding that more than one tool or service may be preferable
- know that planning and advocacy are just as important as directly managing material
- seek “communities of practice” outside of your organization.
POWRR also stresses that institutions are never alone in the long-term preservation effort. There is an extensive information universe and a number of community maintained tools. These are all practically useable even in smaller institutions with limited budgets.
To follow the growth of technological solution maturity, institutions can use number of freely available tools for audit, self-audit or certification. There are tools suitable for the needs of smaller institutions. In most cases the application of standards like ISO 16363 or ISO 27000 would be unrealistic goal. Alternative tools are available for use in a project planning phase or in assessing the quality of what they already have (like DSA, NESTOR Seal, Platter, DRAMBORA, and NDSA’s Levels of Preservation). Applications of these tools do not require extensive documentation and exorbitant budgets and can help institutions improve trustworthiness of their long-term preservation projects.
Pragmatic and practical approaches to digital preservation try to solve complex issues in ‘real life’ projects with respect to available financing resources and technologies. The goal remains the same: to preserve intellectual content of the digital objects unchanged, authentic and accessible with future technologies by users, of whose knowledge base we know nothing today, accessible without the additional information provided by the producer of the information. However, everyday operation of the long-term preservation archive may require pragmatic and temporary solutions. Similarly, the heritage institutions must select documents which should be preserved for long term. Unfortunately heritage institutions will never have the capacity to preserve everything from the digital universe.
A simple example of the evaluation of long-term preservation maturity might be the NDSA model (NDSA’s Levels of Preservation). The model helps to identify where institutions can focus the effort and how to prioritize. The model shows quite clearly four levels of maturity digital preservation in five areas. All the components of a prior level are prerequisites for building systems and processes in the following level. The long-term preservation plan can later be expanded to include more details for each area that are specific to the possibilities and goals of the institution. The levels can be applied to defined collections or to more complex systems preserving more digital collections.
Storage and Geographic Location
File Fixity and Data Integrity
Figure 1 NDSA’s Levels of Preservation, OWENS, 2012
3 OAIS reference model
The bases for long-term preservation terminology and archiving systems design lies in the OAIS reference model (ISO 14721). The concepts laid out in OAIS are more complex than the terminology of the NDSA’s Levels of Preservation. The OAIS model has almost 20 years of history. It came into to existence in the middle of 1990s, when the archival and library community felt the need for a general framework describing common terminology for further development of archiving systems for digital data. CCSDS (Consultative Committee for Space Data Systems) took up the challenge of organizing the work on this standard, which resulted in the publication of the OAIS reference model and was published in 2003 as international standard ISO 14721:2003. The last updated version of the ISO standard from 2012 exists in Czech translation as ČSN ISO 14721. The OAIS reference model proved to be particularly viable and is today widely used in culture heritage institutions as well as the commercial sector. It is rather general and thus opens up wide options in implementation methods. The OAIS reference model defines:
- Terminological dictionary for the area of long-term preservation in archives and repositories, which is understandable to the professional public
- Information model, which describes in detail the recommended structure and content of the Archival information packages (AIP). It details what metadata should be stored with the archived content itself and defines the complete set of metadata called Preservation Description Information – PDI )
- Functional model of the preservation digital archive. The functionalities of the long-term preservation archive built in line with the OAIS concepts are described in six functional entities: Ingest, Archival Storage, Data Management, Administration, Access and Preservation Planning. Here the model describes the key processes of the archive and its functional components.
The current situation of the standard and its impact on the long-term archiving community is well described in the second edition of the B. Lavoies The Open Archival Information System (OAIS) Reference Model: Introductory Guide. Lavoie, among other, mentions development of other standards in the area of long-term preservation, which were inspired or derived from OAIS (as metadata de-facto standards METS, PREMIS, or further standards like ISO 16 363 a ISO 16 919 used to assess the quality of long-term digital archiving)
Figure 2 OAIS reference model functional entities
4 Digital preservation practical tools
In the past 15 years, the projects in long-term digital preservation research and practice catalyzed the creation of a huge body of tools, methodologies and best practices. Most of these solutions are freely available and are indispensable for many institutions. Practicing institutions often use freely available components of operating systems open source tools like imagemagick, Ghostscript, Open office for formats conversions, OCR, hash generation and checks, and so on. Preservation specific tools, DROID, FIDO, SIEGFRIED, JHOVE a JHOVE2, FITS, Jpylyzer, mediaInfo, ffprobe, Exiftool, New Zealand Metadata Extractor, Apache Tika, PDFbox, VeraPDF, are critical for many archives when carrying out processes related to format validation, technical metadata extraction, format identification etc. There are a number of methodologies and examples of long-term preservation strategies and policies, tools and test beds, which can help also in this area.
Attempts to build complete solutions for long-term preservation started at the moment of publication of the OAIS. The first generation of logical long-term preservation systems date back to the beginning of the new millennia. Among the first institutions attempting to build such systems were the Royal Library of Netherlands with IBM DIAS; DAITSS was developed in the Florida digital archive beginning in 2005; XENA was created by the National Archives in Australia. The second generation of the long-term preservation systems made some steps ahead (like SDB/Preservica, Rosetta, and also RODA or Archivematica), by learning from the first generation experiences and built on the results of research projects financed from the EU, the US , or in other countries (SCAPE, Planets, NDIIPP etc). Since 2009 some open source systems appeared with wider ambitions to fulfill more of the OAIS derived requirements.
Many institutions (for example, national libraries in France, Netherlands, Switzerland, Denmark etc) build solutions tailored to their needs and environments from different commercial and open source components, which they bind together. Not much documentation is available about these solutions. Often they are not available as ‘off the shelf’ products In the area of business archiving, some concepts appeared to widen the scope of standard functionalities of the classical ECM (Electronic Content Management) systems informed by functions expected in the long-term digital preservation (see for example (see Korb, J., & Strodl or Ferle).
5 LTP Pilot project
The last two years brought more attention to the LTP system, Archivematica. Archivematica was evaluated for Czech purposes in the project 516R1/2014, LTP Pilot, financed by the CESNET Development Fund. Besides the holder of the grant (Computing Center at Masaryk University in Brno) there were two other institutions participating in this project (Moravian Library and University of South Bohemia). A number of other Czech institutions experimented with Archivematica in the recent two years (for example the central library of the Academy of Sciences). The Archivematica system is one of the components of the solution currently under development in the National Archives of the Czech Republic. The Archivematica system is developed and supported by Artefactual Ltd.  together with a number of other higher education institutions and archiving institutions in the North America and Europe under the auspices of UNESCO.
The goal of the LTP Pilot project was to test the Archivematica system functionalities in integration with the digital storage infrastructure of CESNET, getting curatorial experience with the Archivematica workflow and configuration of the workflow. Various test collections were ingested. The system was evaluated from the point of view of OAIS compliancy. Robustness and scalability also was taken into consideration.
Archivematica fulfills the functionalities of the Ingest and Archival storage OAIS modules. The testing showed that the system is not very robust, the performance has some limits, and the documentation is far from perfect. However, the workflow connecting various micorservices can process various data types. Data with or without descriptive metadata can be ingested, in package formats or without it. Anything can be ingested in some way or other and the system generated AIP packages which contain all the information required by the OAIS information model. Here Archivematica relays on the usual standards (METS, PREMIS, Dublin Core) and the packages are packaged into BagIt format. While testing ingest, all existing transfer methods were used and some scripts were created to form the incoming data into the standard transfer format expected by Archivematica. The tools integrated in Archivematica workflow were tested (FIDO, FITS, JHOVE) and a couple of other tools were linked into the workflow to see the complexity of this process.
Archivematica is not a repository in the sense of which we usually understand it. It’s not a system that would provide functionality for the management of ingested and preserved AIP packages or that could be used to provide end user access. These functions can be implemented outside Archivematica (access) or the API can be used in combination with some external systems for content management (AIP update, metadata management etc.). Institutions often search systems that will help them to manage the data and work with it. They do not need solely one system that will help them to fulfill basic OAIS derived requirements, but also a system supporting effective management of the archived content. In this respect Archivematica needs further development or integration with other systems. More complete solutions for long-term preservation and access are created with the use of Archivematica in combination with other systems such as DSPACE, DURASPACE, Islandora, iRods and other HSM solutions..
Long-term digital preservation is constantly evolving area. While some actualities remain the same, the tools, systems and technologies evolve relatively quickly. Digital preservation is in constant flux. It came to exist from an acute need to cope with specific characteristics of digital objects, which are different than analogue objects in many respects. The problems which arise in digital objects management are rather different than the issues inherent in caring for physical documents. This need produced standards like OAIS and tools like JHOVE, and later led to more complex LTP systems. In parallel, research projects financed out of the EU and other funds expanded the horizons of digital preservation. Digital preservation became a standard agenda at the end of the last decade that archiving institutions took up, and started to conduct preliminary audits. Digital preservation became the daily bread for many; while others have still not decided how to begin.
The goal of this text was to point to practical and pragmatic options in digital preservation. We think it makes no sense to wait for perfect solutions or huge financing. It’s possible that no perfect solutions for long-term digital preservation will ever exist. Even if we are able to build the mythical perfect solution, part of our data will be already lost while waiting for perfection to come to pass.
The academic discourses about digital preservation, discussion of the terminology or meaning of OAIS concepts and relations to other concepts, often with no real practical experience with daily data management or preserving access, do not help heritage institutions. What could help them are simple and practical tools, or examples of technical architectures using freely available tools. Long-term digital preservation will always be community effort. No institution or individual can do it without information and tools provided by various communities of technical experts, without the support of system administrators, hardware and storage experts, and developers, without the support of the management or political support of the projects. The key is to share the information and experience across institutional domains and states.
Long-term preservation is not a technical issue. Technical problems can be solved by technical tools. The bigger risk is the lack of courage and will to start to cope with digital preservation practically, even if we do not have a perfect solution, unlimited resources or complete technical expertise.
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 LIBRARY OF CONGRESS. About – Digital Preservation (Library of Congress) [online]. [s.a.] [Accessed 2015-10-03]. Online: http://www.digitalpreservation.gov/about/.
 For example the recommendations here: http://www.digitalpreservation.gov/personalarchiving/.
 FOJTŮ, Andrea, Jan HUTAŘ a Marek MELICHAR. Dlouhodobá ochrana digitálních dokumentů a projekt NDK. In: Knihovny současnosti 2011: Sborník z 19. konference, konané ve dnech 13.–15. září 2011 v Českých Budějovicích. Ostrava: Sdružení knihoven ČR, 2011, s. 73–79. ISBN 978-80-86249-62-9. Dostupné také z: http://www.sdruk.cz/data/xinha/sdruk/ks2011/sbornik_2011.pdf.
 MINER, M. From Theory to Action: A Pragmatic Approach to Digital Preservation Strategies and Tools. In: SAA Research Forum, Joint Annual Meeting of CoSA, NAGARA, and SAA, Washington, DC. Aug. 10–16, 2014. Online: http://powrr-wiki.lib.niu.edu/images/6/69/POWRR_outcomes.pdf.
 ISO 27000:2014. Information technology -- Security techniques -- Information security management systems -- Overview and vocabulary. Geneva: International Organization for Standardization, 2014. 31 s.
 Data Seal of Approval – http://datasealofapproval.org/en/, případně český překlad na http://dsa.cuni.cz/; Nestor Seal – http://www.langzeitarchivierung.de/Subsites/nestor/EN/nestor-Siegel/siegel_node.html, Platter – dostupný česky na http://www.ndk.cz/platter-cz/Platter.pdf; DRAMBORA – http://www.repositoryaudit.eu/; NDSA Levels of Preservation – http://www.digitalpreservation.gov/ndsa/activities/levels.html
 LIBRARY OF CONGRESS. NDSA Levels of Preservation – NDSA – Digital Preservation (Library of Congress). [online]. [s.a.] [Accessed 2015-10-03]. Online: http://www.digitalpreservation.gov/ndsa/activities/levels.html.
 WERF, Titia van der a WERF, Bram van der. The paradox of selection in the digital age. In: IFLA WLIC 2014, 16–22 August 2014, Lyon, France. Dostupné také z: http://library.ifla.org/1042/1/138-vanderwerf-en.pdf.
 LIBRARY OF CONGRESS. NDSA Levels of Preservation – NDSA – Digital Preservation (Library of Congress). [online]. [s.a.] [Accessed 2015-10-03]. Dostupné z: http://www.digitalpreservation.gov/ndsa/activities/levels.html
 OWENS, T. NDSA Levels of Digital Preservation: Release Candidate One. In: The Signal: Digital Preservation [online]. Library of Congress, 2012 [Accessed 2015-10-03]. Online: http://blogs.loc.gov/digitalpreservation/2012/11/ndsa-levels-of-digital-preservation-release-candidate-one/.
 ISO 14721:2012. Space data and information transfer systems – Open archival information system (OAIS) – Reference model. Geneva: International Organization for Standardization, 2012. 126 s. a ČSN ISO 14721. Systémy pro přenos dat a informací z kosmického prostoru – Otevřený archivační informační systém – Referenční model. Praha: Úřad pro technickou normalizaci, metrologii a státní zkušebnictví, 2014.
 FERLE, Christoph H. Marktstudie digitale Langzeitarchivierung: im Spannungsfeld zwischen Digital Preservation und Enterprise Information Archiving. Stuttgart: Fraunhofer, 2012. Online also from : http://www.swm.iao.fraunhofer.de/content/dam/swm/de/documents/Marktstudie_Digitale_Langzeitarchivierung_web.pdf.
 LAVOIE, Brian. The Open Archival Information System (OAIS) Reference Model: Introductory Guide (2nd Edition). Digital Preservation Coalition, 2014. 33 s. Online: http://dx.doi.org/10.7207/TWR14-02.
 METS – Metadata Encoding and Transmission System, see http://www.loc.gov/standards/mets/.
 PREMIS – Preservation Metadata: Implementation Strategies, see http://www.loc.gov/standards/premis/.
 ISO 16919:2014. Space data and information transfer systems -- Requirements for bodies providing audit and certification of candidate trustworthy digital repositories. Geneva: International Organization for Standardization, 2014. 22 s.
 CONSULTATIVE COMMITTEE FOR SPACE DATA SYSTEMS. Reference Model for an Open Archival Information System (OAIS): CCSDS 650.0-B-1 [online]. Washington (DC): Consultative Committee for Space Data Systems, January 2002 [Accessed 2015-07-28]. s. 4-1. Online: http://public.ccsds.org/publications/archive/650x0b1.PDF.
 DROID – http://www.nationalarchives.gov.uk/information-management/manage-information/preserving-digital-records/droid/; FIDO – http://openpreservation.org/technology/products/fido/; SIEGFRIED – http://www.itforarchivists.com/siegfried; JHOVE – http://jhove.sourceforge.net/; JHOVE2 – https://bitbucket.org/jhove2/main/wiki/Home; FITS – http://projects.iq.harvard.edu/fits/fits-xml; Jpylyzer – http://jpylyzer.openpreservation.org/; MediaInfo – https://mediaarea.net/cs/MediaInfo; ffprobe – https://ffmpeg.org/ffprobe.html; ExifTool – http://www.sno.phy.queensu.ca/~phil/exiftool/; New Zealand Metadata Extraktor – http://meta-extractor.sourceforge.net/; Apache Tika – https://tika.apache.org/; Apache PDFbox – https://pdfbox.apache.org/; VeraPDF – http://openpreservation.org/about/projects/verapdf/
 DAITSS – https://daitss.fcla.edu/
 XENA – http://xena.sourceforge.net/
 Rosetta – http://www.exlibrisgroup.com/category/RosettaOverview; Preservica – http://preservica.com/; Archivematica – https://www.archivematica.org/en/; RODA – http://www.roda-community.org/
 SCAPE – http://www.scape-project.eu/; Planets – http://www.planets-project.eu/; NDIIPP (National Digital Information Infrastructure and Preservation Program) – http://www.digitalpreservation.gov/
 KORB, J., & STRODL, S. Digital preservation for enterprise content: a gap-analysis between ECM and OAIS. In 7th International Conference on Preservation of Digital Objects, Vienna (pp. 221–228). Též česky na: https://duha.mzk.cz/clanky/dlouhodoba-ochrana-podnikovych-dokumentu-analyza-rozdilu-mezi-ecm-oais.
 FERLE, Christoph H. Marktstudie digitale Langzeitarchivierung: im Spannungsfeld zwischen Digital Preservation und Enterprise Information Archiving. Stuttgart: Fraunhofer, 2012. Online: http://www.swm.iao.fraunhofer.de/content/dam/swm/de/documents/Marktstudie_Digitale_Langzeitarchivierung_web.pdf.
KLINDT, M. a AMERHEIM, K. One core preservation system for all your data. No exceptions!, In iPRES 2015, 2-6.11.2015, Chapel Hill, USA. Preprint provided by M. Klindt was available to the authors in the time of writing this text.