Preserving Digital Information in the Face of Obsolescence
Digital Preservation Techniques
Digital preservation techniques aim to maintain the means to interpret and access information in the face of technical obsolescence. These techniques include migrating digital content to newer systems and using sustainable file formats.
But can we preserve bit sequences, logical objects and presentations without changing their properties? The answer is yes, through responsible strategies for detecting unintentional changes and reactions to them.
Resilience
Resilience is a preservation technique that uses multiple copies of digital information on different types of media and devices to reduce the risk of loss. These are often stored in geographically distributed locations, and the information is actively maintained using techniques such as regular migration to new platforms and backups that include checking for corruption.
The goal of this approach is to address the fact that operating systems, hardware and software become obsolete over time. It is important to note that this is a different issue than obsolescence in the sense of deterioration, as it refers to the technical capability of digital media and storage.
Institutions can also use a variety of tools to create and archive digital content, including an ILS for collection management, an institutional repository for research data, a web archiving program, etc. Some of these programs may not be compatible with each other, and interviewees indicated that a lack of coordination between these systems is a common challenge.
Migration
The digital preservation process is an ongoing activity that requires proactive management. Although digitisation itself is an important part of the preservation process, it’s also essential that your institution has plans in place to preserve the results of digitisation, as well as the original archival material.
Migration is the transformation of a digital resource into a file format that is independent of the hardware and software that were used to create it. It is an important digital preservation technique because it can help to overcome technical obsolescence.
Migration can be achieved by reformatting or converting the digital information into a new format, for example from a proprietary to an open source file. This can be supplemented by file format monitoring, which is a complimentary preservation action that can inform the migration decisions made. Migration is a common approach for preserving electronic publications, but it can be problematic for more complex resources and application software (such as games or executable files). Emulation can be used instead of migration in these cases.
Refreshing
Refreshing involves transferring data between different types of storage media so that the bit stream is not lost. This is particularly important because new hardware and software programs are constantly appearing, making existing information obsolete and sometimes inaccessible.
It is also necessary because many kinds of physical media (e.g. magnetic tapes) are susceptible to deterioration over time. Despite the high degree of dependency that digital information has on its technical environment, there are no widely accepted methods of preservation. This has led to the term ‘Digital Dark Age’ in which vast amounts of the world’s knowledge and cultural heritage is at risk of being lost forever.
There are numerous digital preservation projects that are trying to address these issues. These include: digital reformatting, migration, emulation, replication and refreshing. The CAMiLEON project (Digital Audiovisual Reformatting, Emulation and Long-Term Access through Refreshing) is one example of an experimental emulation-based digital preservation strategy. This approach has the potential to retain functionality and ‘look and feel’ as well as to reduce costs over time.
Preservation Formats
A preservation file format is a specific version of a digital file that has been designed for long-term preservation use. It is distinct from access formats, web publication formats and, in some cases, preferred digitization formats.
In general, it is preferable to select preservation formats that have been extensively adopted by communities of users and developers. Wide adoption means that there is a greater chance that software and tools can be developed to support the format in the future.
In addition, migration and encapsulation techniques are more successful for resources that have been saved in widely used formats. The goal of a good preservation strategy is to reduce the number of different formats in your collections, as this can lead to higher storage overheads and increased complexity for your staff. To help you achieve this, your organisation should consider identifying a set of standards for the types of content it holds and working with others who hold similar materials to identify their preferred options.
