October 2002

Data Extinction

Continued from page 2

By Claire Tristram

Migration: Digital Transplant Operations

One of the most common methods for preserving digital information is migration, where the bits in a file or program are altered to make them readable by new hardware and operating systems. It's what happens when you open an old document, such as a Microsoft Word 95 file, with a new iteration of the same software, say Microsoft Office 2001. The drawbacks? Each file needs to be opened, converted and saved individually, a process that grows impossibly large when you consider a librarian's or archivist's initiative to save as much of the historical record as possible. And eventually even the most meticulous of software companies stops supporting old versions of its products. If a file has not been migrated before that time, it's digital gibberish.

Worse, each time a file is migrated, some information is irreversibly lost. "Imagine someone saying, Okay, the way we're going to preserve Rembrandt is that five years from now we're going to have another artist come in and copy his paintings, and then we'll throw away the original,'" says Rand's Rothenberg. "And so on after another five years. The notion is laughable with art, because you know that every time you copy, you corrupt. It's the same with computers."

Migrating text files is hard enough; migrating application software is even more so. Indeed, the term "migrating" is a misnomer, since it often means throwing out the old program and writing an entirely new one in a new programming language, a process that programmers prefer to call "porting." The new program may look the same on the monitor, but underneath it is new. No matter how carefully software engineers have worked to simulate the old program, every line of code is different, with new bugs and new idiosyncrasies.

In any case, it's rarely the goal of the new program to simulate the old one exactly; it's far more common for programmers to want to improve upon the past. That's a goal that keeps computer science advancing at an exponential rate, and it probably also explains why the technical problem of preserving the past has received so little attention from those who helped create the problem in the first place.

"Computer scientists are in a profession where there is virtually no need for historical information," says Abby Smith. "They don't need information from the 1650s or the 1940s. They are used to things superseding what came before. For those in the humanities, there is no such notion. They work by accumulation, not replacement."