One of the fundamental issues facing libraries involves the long-term preservation of information. While this issue applies to all aspects of a library's collection, my main concern as a technologist involves those in electronic form. We need to ensure that our collections will be available for all future generations, regardless of their format.
Materials printed on paper have proven to be truly long lasting. Manuscripts from hundreds, if not thousands, of years have survived to our generation. When we think of preserving digital information for posterity, the ideal continues to be eons, not mere decades.
As libraries, information centers, museums, and archives become involved in creating collections of digitized materials, enormous challenges emerge when it comes to guaranteeing permanent access. Digital technologies have only been around for the last few decades, and lack a track record of long-term preservation.
As I follow the recent trends and initiatives related to digital collections and digital preservation, one theme that continually arises involves the Open Archival Information Systems reference model. This framework describes a set of principles and methodologies involved in the creation of digital collections that can be trusted to provide permanent storage and access of their materials. Well take a quick look at OAIS later in the article.
The challenge of changing technologies
Technologies involved in the storage and presentation of digital information change continuously. Removable disks have evolved through many formats over the last 20 years. Remember the 5-¼ inch single density floppy disks that held 360KB of data? How many computers remain equipped with drives that can read them today? Even 3 ½ inch disk drives seem to be fading from the scene. Optical discs race through the same transitions. In my collection of old computer gear, I recently came across a 12-inch laser disc. Very few computers would be able to read the data on it today. CD-ROM's have been a mainstay for many years, but now DVD is gaining a stronghold. Given the history of technology, we can only assume that any given method of storing information will be transient, and the cycles of life expectancy for any given format may even become shorter as time goes on.
Another problem revolves around the various file formats used to store information and the software used to create and view these formats. The way that text, images, sound, and video can be stored and accessed by computers has gone through many transitions. The software involved with creating and viewing digital information evolves rapidly, as do the hardware platforms and operating systems involved. Word processors, graphics programs, and video editing environments evolve quickly, and there are no guarantees that each new version will be backwards compatible with previous versions.
Digital media fall prey to physical deterioration. It is a common misconception that once recorded onto standard media, that digital information will last forever. Magnetic tape, optical discs, and hard disk drives all have limitations on how long their data will last if left unattended. Some CD-ROM manufacturers claim life expectancies of 200 years without data loss. But such assertions are not undisputed and environmental conditions can definitely accelerate deterioration. Optical media generally offer longer life than magnetic, but neither approaches the ideal of permanence. Yet, the real problem is obsolesce rather than deterioration. Even if the data were to stay intact on the media for 200 years, would there be playback equipment available? Given the rapid change in hardware already noted, it seems highly unlikely that compatible equipment would exist.
I don't intend to paint a negative picture regarding the long-term viability of digital information. My point is to show the challenges that must be met. Strategies, methodologies, and technologies for preservation are being developed and refined, and are a key component of any digital collection.
Basic methods for preserving digital content
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