Digital object properties
Understanding the properties of digital objects and materials is a critical part of any technical measures that are devised to facilitate their long-term preservation. Whilst some digital materials (e.g. plain text) are fairly straightforward to describe and maintain, other materials such as multimedia database driven web pages, or software applications, are so complex that designing strategies to ensure they can be viewed and used in exactly the same way over a ten or twenty year timescale (or longer) is not realistic. In the majority of cases, as the active management of digital materials is carried out over time (a principle that is central to digital preservation practice) assessment will be required at planned intervals to determine the best way of maintaining the effectiveness and value of the digital assets that an organisation, group or individual has responsibility for.
Regardless of the preservation measure that is selected, usually some form of emulation or migration strategy, it is likely that the digital material in question may be subject to subtle or blatant alterations to way it can be accessed, used or rendered following completion of the preservation action. Taking a simple example, migrating a .tif image file to JPEG2000 format, which an organisation might consider doing as part of a long-term policy to make more economic use of institutional storage space, might be considered an un-archival approach as the quality of the original image will be compromised as a result of the compression that would normally be applied to achieve significant file size reductions. The counter-argument would be, however, that the human eye is not capable of noticing the degradation in the image so therefore this loss of quality is an acceptable risk to secure a more sustainable future for the archive more generally.
Preserving the properties of digital objects needs to be a balance between issues of quality and practicality and JISC is committed to supporting various strands of work which will enable practitioners to manage digital materials according to their context and type.
Relevant work