The goal of this preservation policy is to outline how to preserve the born digital content and the accompanying online virtual tour and exhibit. The digital resources of projects such as this tend to be dynamic as they can be enriched and extended over time. A lifecycle management approach must therefore be adopted. This means that preservation must begin at the creation and design stage of the project in order for it to be successful. This is widely acknowledged to be best practice and is the most cost effective way in the long term. The ultimate goal is to preserve the digital objects so that they remain accessible and viable in the long term and, additionally, so that the component parts may be re-used in the future in other projects.
Consideration has been given to the challenges related to the preservation of digital resources, and sustained long term access to the online tour and exhibition and its component parts. In particular, consideration has been given to technological obsolescence of both hardware and software, and the available staffing and funding resources available to the institution. Viable appraisal and selection criteria for digital materials need to take account of factors which assume greater importance than for non-digital materials, such as intellectual property rights and the need to preserve more contextual information about the materials. Metadata is therefore a vital consideration so that there is sufficient contextual information available to allow the digital materials to be searched or manipulated. In the future, users should be able to interrogate the old data to produce new results.
The first step is to perform a collections inventory to locate the materials that will be digitised and included in the online exhibit. It is then necessary to count and describe all of the identified material. After this, all relevant information from acquisition records, the collection itself, and any other useful resource should be gathered. The location, inventory number, type of physical medium and any identifying information should be recorded. In addition, it will be necessary to record anything that is known about the hardware, operating systems and software used to create the files. It is important that consistent terms are used in the descriptions contained in these records. Relevant intellectual property rights information about each object should be established.
This is the initial stage of the preservation strategy. The bitstream of every archival digital object should be preserved in its original form indefinitely. This means that more complex preservation may be carried out, either when there are resources available or when there have been advances in preservation techniques, because the original bitstream can always be returned to. To ensure that unaltered bitstreams are preserved intact over time, so that the authenticity of the digital object is not compromised, the following steps should be taken:
- Multiple copies of the bitstreams should be maintained. Best practice is that at least three copies should be kept. The copies should be isolated from each other, both geographically, and technologically, i.e., stored on different media types. (Where the same type of media is used, it is a good idea to use different brands or batches of the media to minimise the risk of faults which may occur in a particular batch or brand.)
- There should be ongoing fixity and integrity checks using checksums.
- Security controls should be put in place, i.e., password controls, firewalls, anti-virus.
- Permissions should be controlled and system security should be rigorously tested.
- The digital object should not be altered in any way.
This is the second stage of the digital preservation strategy. Migration is defined as the copying or conversion of digital objects from one technology to another, whilst preserving their significant properties. Migration focuses on the digital object itself. As such, it aims to change the object in such a way that hardware and software developments will not affect its accessibility. It applies to hardware, i.e., the copying of digital objects from one generation or configuration of hardware to another, and software, i.e., the transferring of digital objects from one software application or file format to another. It is important that migration is fully documented by metadata, and ideally it should also be reversible. In this project, the digital objects should be migrated to standard format on ingest into the project. This is known as normalisation. In order to control complexity and cost, only a limited number of standardised file formats will be supported; all digital objects should be migrated to an appropriate supported format on ingest. All digital objects of a particular type will be converted into a single chosen file format that is thought to embody the best overall compromise among characteristics like functionality, longevity and preservability. Normalisation is a more cost effective option than migrating to a wider range of formats. Alternatively, the project may limit this approach to just one preservation-friendly format, converting all digital objects to this format on ingest.
There are also some general precautions in relation to storage and handling which can be observed to mitigate the risk of physical degradation, whatever the media employed:
- Digital materials must be stored in a stable, controlled environment. Fluctuations in temperature or humidity should be avoided. For mixed collections the suggested temperature is around 20ºC and relative humidity 40%.
- Keep storage areas free of contaminants.
- Media should be stored in closed metal cabinets which are electrically grounded.
- Media should be shelved vertically rather than stacked.
- Minimise light levels.
- Store any non-digital accompanying materials in appropriate conditions.
- Media should always be stored in the correct cases, preferably a suitable archival quality case.
- Media should be visually checked for signs of damage on a regular basis.
- Media should be allowed to acclimatise to any new temperature/humidity before use and be returned to controlled storage immediately after use.
- Minimise the handling of archival media; restrict to trained staff.
- Establish guidelines and procedures for acclimatising media if moving from significantly different storage conditions.
- Keep access devices well maintained and clean.
Currently the technological knowledge or awareness to maintain digital objects for long periods of time does not exist. For this reason, no preservation strategy is sufficient to ensure the long term preservation of digital objects. As such, the project should expect to implement different preservation strategies over time. Therefore, the digital material should be continually reappraised to establish what further preservation actions need to be taken.
- Brown, A. Practical digital preservation: a how-to guide for organizations of any size. Facet Press, London, 2013. Print.
- Erway, R. “You’ve Got to Walk Before You Can Run: First Steps for Managing Born-Digital Content Received on Physical Media.” 2012. Web. 20 November 2014.
- Lavoie, B. F. Technology Watch Report 04-01: The Open Archival Information System Reference Model: Introductory Guide. Digital Preservation Coalition. Print.
- Ross, H. Preserving Digital Materials. K.G. Sauer. Berlin. 2008. E-book. 20 November 2014.
- “Selecting the Right Preservation Strategy.” Paradigm. January 2008. Web. 25 November 2014.
- Digital Preservation Handbook. Digital preservation Coalition. 2012. Web. 23 November 2014.