An Introduction to Preservation of Digital Media
Introduction
Digital Preservation is the active management and maintenance of digital objects (the files, or groups of files, that contain information in digital form) so they can be accessed and used by future users. It involves planning, resource allocation, and application of preservation methods and technologies, and 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 to ensure its authenticity, accessibility and usability.
Scope
Preserving and archiving digital media covers a wide and varied areas from emails relating to the works of government and businesses, the videos uploaded onto platforms such as Youtube or TikTok, to digital copies of older physical based information such as historic documents or records.
It is possible to distinguish among three distinct but not mutually exclusive preservation applications of digital technologies and media, defined in part by the possible purposes that the product may serve for end users.
Protect Originals: The most common application of digital technologies in an archive or library is to create digital copies of sufficient quality that they can be used for ready reference in lieu of casual browsing through the original sources. Preservation goals are met because the original documents can be protected by limiting access to them. Examples include image reference files of photograph, clipping, or vertical files which permit the identification of individual items requiring closer study. The original order of the collection, or a book, is "frozen" much like microfilm sets images in a linear array.
Represent Originals: A digital system that represents the information content of the original sources in such detail that the system can be used to fulfil most, if not all, of the research and learning potential of the original media.
Transcend Originals: In a very small number of applications, digital imaging promises too generate a product that can be used for purposes that are impossible to achieve with the original sources. For example, when old films have been digitised, enhanced and restored from the original/recovered film. The BBC did this to recover lost episodes of Doctor Who and Dad's Army.
Challenges
Keeping the data
Every digital file is formed from a series of zeros and ones, or bits (binary digits). These streams of bits need to be captured and retained over time, without loss or damage, to ensure the survival of digital materials. There are an array of threats to any attempt at preserving these bits. Storage media can decay over time, leading to corrupted files. Storage media may become obsolete and unsupported by contemporary computers and the software that understands and provides access to them. The bits may be ignored, abandoned, accidentally deleted or maliciously destroyed. Removable media could be left on a shelf and forgotten, files stored on a shared network drive might be left without an owner, or a third party cloud storage provider could go out of business.
Maintaining a systematic process for bit preservation remains a fundamental requirement in ensuring long term digital preservation. Storage media must be monitored and refreshed. Redundancy must be introduced by replicating or backing up files, introducing diversity in dependent technologies and avoiding catastrophic disaster at a single geographical location. Checksums must be generated and frequently recalculated to identify any loss and ensure that the integrity of the bits can be verified in an efficient and automated manner. The locations in which digital materials are stored should be carefully recorded, and responsibility for their preservation allocated.
Keeping the meaning of the data
Reconstructing the information that is encoded within a stream of a bits typically requires computer software that is designed to render, manipulate, analyse or otherwise interact with the particular encoding or format of the data. Over time, the encodings (or file formats) may change, and the software applications that interact with them may go in and out of favour. Although unusual for well known file formats, less well used file formats may become obsolete over time, as the software that renders them is no longer supported.
Understanding the technology on which particular digital materials are dependent enables appropriate action to be taken to ensure their preservation. A considered preservation planning process might result in the migration of digital files from format to format, the emulation of obsolete software, or the employment of alternative software applications to render the data. Each of the options presents its own advantages and disadvantages and these need to be evaluated carefully, possibly on a case by case basis.
Maintaining the trust in the data
Digital materials have the potential to remain fluid over time, being edited or altered with ease, being damaged by media failure, or decoded into human readable information in an unreliable or inaccurate manner by rendering software. For an end user to have trust in the result of digital preservation work it requires careful consideration of the entire lifecycle of the digital materials and who or what has interacted with them over time. Information management systems need to be able to link to essential contextual information regarding the business procedures of the creating agency. Authenticity and integrity of digital resources can be equally important in other sectors. For example, scholars will need to feel confident that references they cite will stay the same over time, courts of law will need to be assured that material can withstand legal evidential requirements, government departments may well have legally enforceable requirements regarding authenticity, and so on. This issue overlaps with both legal and organisational issues and it may be one which is best resolved within individual sectors rather than through generic procedures.
The application of data integrity techniques and the maintenance of audit trails can provide confidence that a digital object has remained unchanged (except by necessary preservation action) since deposit in an archive. Ultimately its authenticity to a user may depend much more on the broader trustworthiness of the preserving organisation as a whole. Maintaining high quality preservation processes based on current best practice and validated by appropriate audit and certification will be crucial.
Keeping the context of the data and its dependencies
The meaning of digital information can be dependent on additional information that may have been implicit within the context it was originally created or used in, but less clear when revisited at a later date. Identifying, understanding and capturing relevant contextual information can be vital to a successful preservation effort. This might be as simple as capturing the units of measurement used within a spreadsheet, the scale of a map, or the point of origin within a CAD drawing. As digital information continues to be created in a more complex and interconnected manner, it may be necessary to retain the place of particular digital materials within a wider context of associated information resources. What may be seemingly simple and stand alone documents may actually depend on related files, referenced fonts and may have pointers to related information on the web. What might be viewed as a simple web page may have been generated on the fly from live data sourced from different locations on the Internet.
Understanding the data, how it will be used, its dependencies and its context will enable it to be captured for preservation in an appropriate manner and documented in a sufficiently explicit manner to enable the intellectual content to be retained and understood on into the future.
Conclusion
This is one of those topics which at first seems it should be simple but quickly becomes a far complicated issue as you begin to take all the necessary steps and measures to ensure effective preservation of digital media. Hopefully, this has been interesting to read about. I would recommend further reading on this topic as it will potentially affect everything we do as a considerable part of our lives are now all on online and how we manage it will be important in future or in some cases it is already vital today.
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