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Avoiding a Digital Dark Age

Data longevity depends on both the storage medium and the ability to decipher the information

Kurt D. Bollacker


2010-03CompSciBollackerFE.jpgClick to Enlarge ImageIn the 1960s, NASA launched Lunar Orbiter 1, which took breathtaking, famous photographs of the Earth juxtaposed with the Moon. In their rush to get astronauts to the Moon, NASA engineers created a mountain of magnetic tapes containing these important digital images and other space-mission-related data. However, only a specific, rare model of tape drive made for the U.S. military could read these tapes, and at the time (the 1970s to 1980s), NASA had no interest in keeping even one compatible drive in good repair. A heroic NASA archivist kept several donated broken tape drives in her garage for two decades until she was able to gain enough public interest to find experts to repair the drives and help her recover these images.

Contrast this with the opposite problem of the analog Phaistos Disk (above right), which was created some 3,500 years ago and is still in excellent physical condition. All of the data it stores (about 1,300 bits) have been preserved and are easily visible to the human eye. However, this disk shares one unfortunate characteristic with my set of 20-year-old floppy disks: No one can decipher the data on either one. The language in which the Phaistos disk was written has long since been forgotten, just like the software to read my floppies is equally irretrievable.

These two examples demonstrate digital data preservation’s other challenge—comprehensibility. In order to survive, digital data must be understandable by both the machine reading them and the software interpreting them. Luckily, the short lifetime of digital media has forced us to gain some experience in solving this problem—the silver lining of the dark clouds of a looming potential digital dark age. There are at least two effective approaches: choosing data representation technologies wisely and creating mechanisms to reach backward in time from the future.

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