Storage of digital objects Adolf Knoll National Library of the Czech Republic

Basic principles store digital objects in such a way that you can always:  find them – know where they are  identify them – know what they contain  open and access them  manipulate with them  provide access to them to users

Search of realiability image and other data files metadata platform and definitions structural schemes storage media Everything is in motion – we should evaluate its speed and prefer more durable solutions.

Image and data files they should have unique names they sholuld be attached to identification metadata they should be archived in highly used ISO formats (TIFF, JPEG) we should be aware of the fact that the source archival image can be reused e.g. – Czech NL now optimizing access image sets

Metadata openly readable platforms (SGML Family) content markup and possibility to reuse them content description rules with enough granularity reliable storage of metadata awareness that one day they might be migrated e.g, Czech NL migrates now medata sets for ca. 1.3 million digitized page (in continuing production) make them independent of access tools

Structuring and storing Structure metadata and link them to image entities Store the structured units together If creating database access, pay a lot of attention to preservation of the database have always a reference off-line archives for digitized documents

Reference digital archive on-line Disk arrays for access Reference archive of preservation microfilm Reference digital archive of off-line media (CD, mg. tapes) Administration

Media media are not critical for long-term storage the dependence of digital documents on software and hardware environments is critical media can be refreshed always have more independently stored copies

Stability of media vs. obsolescence It seems that the most reliable medium is CD:  obsolete, but well standardized  it contains redundant data for corrections  far from being dead – it is well suitable also for video thanks to new compression standards  cheap  the CD archives should be measured and monitored  do not OVERBURN!

Other media Most data is stored on magnetic tapes  problems with writing software after years, no data redundancy  fragility; tapes should be rewound  mass robotic storages facilities/libraries  self-checking, rewriting, but… Hard disks – backups – more access media DVD, flash cards, …

An example – compact disc scratch from manipulation with reader printing matrix made this scratch metallic coating insuficciency

Origin of damages of CD manipulation scratches – 43% dust – 28% damages incurred in production – 15% Table of Contents errors – 2% Other – 15% Not all of them are critical for readability, but they warn us.

Quality vs. commerce Industrial production works for current users – acceptable quality of media For long-term storage needed more reliable quality Only co-operation with producers is the solution Especially compact discs and magnetic tapes (UNESCO involvement)

Proprietary vs. Open source Open source – we possess resources and can change the product – usually required by academic sphere However: Microsoft, Adobe, Ex-Libris – no chance Society has a consumer character also in more important fields than libraries I.e., work with small and medium enterprises, local companies, try to develop yourselves in harmony and grow both