This is close to my heart. I deal every day with texts and images that are typically 3000-5000 years old. I am constantly amazed both by what is preserved and by what is lost, and I wonder all the time what in 5000 years will be left of our culture. We are not immortal, and languages are not either. And essentially, a data format works in effect as a language. There are several issues I can think of.
1. In the short term (say up to 100 years) there is the issue of data rot. All electronic media becomes unstable. A paper document or printed image can still be read by humans even with holes or damaged portions, as we can compensate for incomplete data far better than a computer. A damaged DVD will rarely even load, but we can piece together a papyrus from scraps and still recover at least some of what the author wanted to record.
2. In the short term, data formats are unlikely to be a major problem. Office 2010 can't read Word 1.0 formats, but one of the features of digital technology since the adoption of home computers has been the desire to emulate either in soft or hard form old computer systems and their software. Atari 2600 and Sega Megadrive games have been duplicated from the original ROM cartridges and emulated as ROM image files on modern systems. This is likely to continue. Mainstream systems in the near future probably won't read VCDs, but people will still be people, curious about their past, and seek to build specialised niche systems to extract and preserve them. This however, depends on the physical survival of at least one original file. Like papyri, the fewer copies existed in the first place, the less chances it will have of surviving long enough for its historical value to be realised and for the transfer of the original data to a new medium.
3. In the long term (1000 years or more) the question becomes one of total cultural disconnect. We have no idea what society will exist 1000 years from now. There is a real possibility that western culture will be a receding part of history, and that our languages, let alone our data formats, will be as incomprehensible to the people of that era as mereotic is to us now. History is not a case of constant technological advancement, as we know. It is entirely feasible that future cultures may not have the technological or archaeological know-how to recover our electronic data from any material that survives that long by chance. On the opposite hand, a more technologically advanced culture may have the same problem, much as we have no idea what some ancient devices are meant to do, even though they use very simple, well understood technologies. Again, an analogue copy has advantages here. Even if one cannot read the language of a text, they can see it is text and see everything that is preserved and work from there. Preserving a movie on film stock has the advantage that anyone can look at it with their own eyes.
Solutions?
* Analogue has the greatest chance of being able to be interpreted, at least to some extent, by future generations.
* Herd protection. Many copies are more likely to pass on something to the future than a few. Spread copies as far and wide as possible, but make "time capsule" back ups as well, not instead of.
* Deliberate protection with an archaeological eye is important. A few very specific factors allow things to survive through time physically. From Egypt, tombs survive, because they were built in the deserts. Very very few homes survive, because they were overwhelmingly built on floodplain. So a good move would to deposit as much material as possible in analogue format ,in an unlikely to be disturbed, climatically stable area with ultra-low humidity and unlikely to be prone to flooding. many government have depositories in locations such as this (in the UK the national archives body utilises an old salt mine for the purpose of storing documents, including the location of nuclear waste dumps).
One solution for an individual to preserve an archive of what matters to them for the distant future would be to build a time capsule containing the relevant media surrounded by silica gel capsules in a thick, reinforced and totally air and moisture tight container made out of a un-reactive metal. The security of the seal closing the container is vitally important, and ideally should consist of multiple layers of protection against water, fungal or insect penetration. One example would be a cylinder with an inner core of thin ultra non-reactive metal with a lid that screws down onto an O-ring sealed lip on the inside, then closed with a welded collar around it. This is in turn enclosed within a much thicker protective outer cylinder of lead, again with all spare space filled with silica gel, and sealed in the same manner. This could then be placed in the sort of environment detailed above. Provided the storage medium is chemically stable (i.e. acid free paper and ink), it should survive, theoretically, for millenia.
