Long Term Digital Information Usability

The Issue of Long Term Digital Information Usability

The world of information is becoming increasingly digital. Major efforts are being made to digitize old analog records, while other records were created digitally in the first place. Many new types of records do not even have a practical analog representation. Yet relatively little has been done to ensure that digital records are accessible and usable far into the future. Historically, analog representations of critical data have been created and stored to ensure future use. In aircraft manufacturing, two-dimensional representations of three-dimensional aircraft designs are often generated and printed out for use in constructing the aircraft.

But these approaches have reached the breaking point. Given the quantity and richness of digital data, long-term usability is an important issue.

Challenges associated with digital records

Everything eventually becomes obsolete or decays: natural languages, paper, cultural context. But while for analog artifacts, life expectancy can often be measured in centuries or longer, for digital artifacts, even a decade may be a long time. This difference in the time to obsolescence and decay makes it much harder to ensure future usability of digital data.

Figure: Obsolescence of analog information versus digital information.

A prerequisite of being able to use an information artifact in the future is the ability to actually have a physical medium containing that artifact. For an analog document, this could be paper or microfilm. For a digital document, it could be a disk drive or a digital tape. If stored properly, we can expect to be able to extract the information from paper or microfilm even after a century or more. For digital media, however, even when stored properly, the bits may be expected to “rot” in well less than a century and, for some types of media, in less than a decade.

Beyond the mere existence of a physical entity containing the information, the digital world brings up a range of issues which barely exist in the analog world. such as the lifetime of the form factor. For example, consider trying to use a 5¼-inch or even 3½-inch floppy disk today.

In addition to the physical aspects of long-term usability, there are also logical aspects. Given a medium containing an information artifact of interest, how does one find the artifact of interest? How does one extract the specific artifact from the medium? How does one understand the information? For analog objects, the answers tend to be very straightforward; this is not the case for digital artifacts. For instance, anyone with knowledge of the right engineering principles can understand an analog design of an aircraft component on paper, since all of the information is explicitly visible. For this same design created by a CAD/CAM program, however, having the sequence of bits in the file representing the design does not suffice; there needs to be a means of transferring the sequence of bits into information that can be consumed by the engineer.

A related perspective on the difference between the analog and digital world is the degree to which analog artifacts stand by themselves while digital artifacts require a deep technology stack to be usable. Even when analog artifacts require technology to see the information, such as microfilm, the technology is simple – often long-lived – and, given the medium, it is easy to envision how to extract the information. For digital artifacts, however, we need a deep technology stack to be able to use the information. Not only do we require the bit sequence composing the actual digital artifact, but we will also likely need an application to interpret the artifact, the middleware used by the application, an operating system compatible with the application, and hardware capable of executing all of the above. If any one of these elements is not available and remedial action is not taken, the digital information artifact will no longer be usable.

What it means to ensure long-term usability

Very simply, ensuring long-term usability means enabling a future user to use a digital information artifact in a way that is natural and makes sense at that future point of use. This includes enabling the user to find the artifact, using the mechanisms that make sense at the time of use. It also comprises recognizing that the purpose for which information is preserved may be subject to change over time. These changes in how we may wish to use the information and the reason we are keeping it for the long term may affect the way we address its future usability. This has the further implication that ensuring long-term usability is not necessarily a static process. Rather, it may change over time as the intended use of the stored artifacts changes.