Preservation of Digital Data by Christian Wellner Based

Preservation of Digital Data by Christian Wellner Based on: Howard Besser. Digital longevity. In: Maxine Sitts (ed. ) Handbook for Digital Projects: A Management Tool for Preservation and Access, 2000 Mary Baker et al. : A Fresh Look at the Reliability of Long-term Digital Storage. In: Proceedings of the 1 st ACM SIGOPS/Euro. Sys European Conference on Computer Systems 2006.

Preservation of Digital Data Motivation Problems: Longevity, Visibility, Custody Proposed Strategies

Motivation Strong trend of digitalizing (historical) data allows more efficient work decreases storage space significantly can be copied easily Negative aspects are however often neglected

Problems of Digital Storage Longevity problems Human „errors“ or catastrophes can still occur (burning a book vs. overwriting a file) Durability of storage devices is physically limited („mutation“ of bits)

Problems of Digital Storage Visibility problems Each storage device needs its special hardware (e. g. floppy drives) Each file format needs its special software (e. g. word processors) Manual decryption of binary code is (in most cases) almost impossible

Problems of Digital Storage Visibility problems Files may be compressed (e. g. JPEG) Companies aim to protect their own formats (e. g. with elaborate encoding) data may only be readable in a certain context (e. g. on websites)

Problems of Digital Storage Custodial problems Who is responsible to keep data accessible for future generations? Regular analysis of the data is required to find latent errors, leading to monetary costs restrictrions by copyright laws (especially if a third party owns the context)

Proposed Strategies Improving longevity Using the safest hardware available Constantly checking the data for latent errors Protect the data against hacking or catastrophes

Proposed Strategies Key strategy: Redundant duplicates „Refreshing“: a copy of the data that is to be preserved is made regularily The data itself is only lost if all copies are lost Important: storing copies in independant places

Proposed Strategies Two general options for visibility Migration: files are translated into newer formats that can be directly accessed Emulation: programs simulate the usage of the processor of the original format Better standardization can also help a lot

Proposed Strategies Solving custodial problems May require some changes in law Allow website owners to preserve third party content if it is needed to display the site Transfer responsibility to preserve it if data changes its owner

Proposed Strategies Meta Data Can be incredibly useful to decipher a file Directly shows how to handle the data But does not give away protected information Can be applied to any format

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