ADS Newsletter Issue 15

Digital preservation and the future of the past

Digital archives have become trendy. Suddenly everyone putting a database and some images on the Internet is calling it a "Digital Archive". But this is misleading. Electronic resources are fragile and digital archives require special care. Here Hamish James, AHDS Collections Manager, describes what it means to be a proper digital archive and looks at international efforts to define standards for digital preservation.

If they think of digital archives at all, most people probably imagine a computer system, comprised of hardware and software connected to a network, that is designed to store and deliver digital resources, such as datasets, documents, digital movies or the like. These 'archives' fall well short of what we would expect from a paperbound archive, lacking the "connotations of preservation of long-term value, statutory authorization and institutional policy" associated with traditional archives.

Benign neglect can be an acceptable state of affairs for traditional archives, but without ongoing attention, information held in a digital form does not survive for long. In addition to the fundamental requirement to back-up data, curators must tackle media degradation and the obsolescence of file formats, software and hardware. Most of us have experienced some of these problems - the old disk that cannot be read any more, the data in a file format we no longer have software to open, or the old software that will not run on our new computer. Parallels to these problems can be seen in the difficulty of deciphering ancient languages or preserving ancient documents, like the famous 'Phaistos Disk' from Crete pictured above. Whereas these problems might only emerge after hundreds of years, in the digital world, they can become significant in a decade or less.

The writing on the Phaistos Disk, found in a Minoan Palace in Southern Crete, defies attempts at being deciphered. Although contemporary with linear A scripts, no other forms of the script are known.

There is no single solution to these problems, but the curators of digital resources can draw upon several strands of research into digital preservation. Approaches range from preserving old hardware, periodic migration of data to new file formats, and the emulation of old software on new computers. The role of a digital archive is to understand these options, selecting the most appropriate method to ensure that information remains accessible.

The most influential work on how a digital archive should operate is the 'Open Archival Information System' (OAIS) reference model, now an ISO standard. The OAIS model was developed to improve the preservation of data collected by NASA during space missions. This model describes in detail the main activities a digital archive must undertake - ingest, data management, archival storage, access, administration and preservation planning. Backup, which is sometimes confused with digital preservation, is a part of one of these activities.

The archive and library professions have also made valuable contributions, identifying the Attributes of a Trusted Digital Repository, and discussing A Metadata Framework to Support the Preservation of Digital Objects.

Research is now becoming more practical. In the UK, for example, The National Archives are running a digital archive and the British Library is also working on these issues. That's why at the AHDS we are redeveloping our own digital archive to handle the rapidly rising volume, and increasing variety, of data deposited with us.

Hamish James
Hamish.James@ahds.ac.uk

For more on digital preservation see 'Preserving Access to Digital Information at: http://www.nla.gov.au/padi/

Digital preservation and the future of the past

In this issue ...