The Obsolescence of Migration: Long-Term-Storage of Digital Code on Stable Optical Media

Abstract

Future accessibility to information requires on one hand a stable media that reliably stores the information content and that, one the other hand offers accessibility with the tools available in the future. Today, institutions have to rely on proprietary technology. Most of them, hard-drives, magnetic tapes, or DVDs, do not fulfill the requirements of long-term stability and accessibility. Thus, an ideal storage solution for archival purposes should meet the following requirements: it should offer high stability, high data density, low costs per GByte, should be easy to handle, undemanding regarding to the infrastructure, and technology independent.An example of a technology independent and reliable method to store data is human readable symbolic code, such as written text. In this case, the interface to access the data is reduced to the eye of the observer. Considering this fact, we propose to investigate a data carrier based on photographic material of high stability, on which digital information of any kind can be stored as visible digital barcode. Thanks to the visibility of the data, it is possible to recover the information with any digital scanning or camera device of appropriate quality. As photographic material is usually based on more than one layer of dyes, each layer can be used as a separate data channel. The quantization depth of each channel leads to a digital code over a higher than binary alphabet. Fragmenting and distributing the data on the film can increase resistance against local deterioration.The available technology at the time of the future digitization and interpretation of the archived information is unknown. Thus, the complexity of information retrieval will be simplified by a sophisticated encoding procedure, an asymmetric approach common in data compression. Such a sophisticated asymmetric codec requires an optimized interaction of information carrier and digital code. We will analyze state of the art photographic material to evaluate its properties. Taking into account the characteristic features of the data carrier, the digital code will be optimized regarding data density, robustness and simplicity. Furthermore, highly sophisticated error correction will be applied to the data to enhance security. The presented approach combines the positive aspects of digital data and an ultra stable medium like microfilm (estimated lifetime up to 500 years at room temperature) and leads to an archival media with an expected storage capacity of up to 700 MByte per sheet (104x148mm2 color microfiche).