Digital Preservation Policies: Technical Considerations SAA Boston: 08-06-2004 Andrea Goethals, FCLA

3 Suggestions Consider your preservation policy a work in progress. Version and date your preservation policy. Separate the more volatile components of your preservation policy from the more stable components. Keep in mind the fact that computers can be time-savers. Automate, Automate, Automate.

SOME of the technical considerations See your handout for the list… Focus for today: file format decisions

File Format = A usually-documented way a single file structures digital content and possibly metadata about that content. File content := (internal metadata) * (content)+

3 File Format Examples TIFF 6.0 XML 1.0 PLAIN TEXT

File Format Decisions in Policy Which file formats to use for 'preservation copies’ (not access copies) might digitize material to this format might convert other digital formats to this format might create a copy of other digital formats in this format Requires value judgments on which formats make good preservation formats

You know a file format is a good preservation format when … It accurately represents the real-world representation Passes the Fidelity Test It should be easy to interpret/copy/present/distribute in the future Passes the Future Test

The Fidelity Test Depends on the original ‘input’ Requirements of oral history vs. a symphony performance

The Future Test Single (free?) publicly-avail. spec. from a reliable source Short clear specification Simple format Includes technical metadata needed to interpret the content Avoids codecs, etc. that require license fees, etc. Relatively long history of use, well-supported Completely self-sufficient, no external file dependencies Doesn’t lose info during a copy-to this format Not dependent on the original ‘input’

Fidelity Test != Future Test A format that fails the “Fidelity Test” can ace the “Future Test”. In the future you can perfectly support a poor representation of the input. (Bad) A format that aces the “Fidelity Test” can fail the “Future Test”. In the future you can't support a faithful representation of the input. (Bad) A format that aces the “Fidelity Test” can ace the “Future Test”. In the future you can perfectly support a faithful representation of the input. (Good)

Tiff 6.0 takes the Future Test Single (free?) publicly-avail. spec. from a reliable source: Yes, freely available from Adobe's website Short clear specification: Yes: 121 well-written pages Simple format: Yes Includes technical metadata needed to interpret the content: Yes, Image File Header and one or more Image File Directories Avoids codecs, etc. that require license fees, etc. : Maybe, if you avoid certain codecs (ex: LZW in TIFF)

Tiff 6.0 takes the Future Test Relatively long history of use, well-supported: Yes, since Summer 1992, good support Completely self-sufficient, no external file dependencies: Yes Doesn’t lose info during a copy-to this format: Yes if you avoid lossy compression (ex: JPEG in TIFF) RESULT: Tiff 6.0 aces the Future Test as long as the codecs used in the Tiffs are restricted.

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