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PREMIS and the National Digital Newspaper Program

Repository of digitized historical newspapers with PREMIS metadata for each file in TIFF, PDF, JP2, and ALTO formats. Lessons learned and how PREMIS is generated and inserted into METS.

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PREMIS and the National Digital Newspaper Program

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  1. PREMIS and the National Digital Newspaper Program Justin Littman Office of Strategic Initiatives, LC jlit@loc.gov

  2. Overview • Repository of digitized, historical newspapers • Implemented PREMIS in 2005 • To date, applied to ~1.2 million digital objects

  3. What we do • PREMIS metadata for each file • TIFF • PDF • JP2 • ALTO • METS (subset of metadata) • PREMIS metadata is included as <techMD> in METS

  4. What we do - example <!--PREMIS technical metadata for digital master for page 1--> <techMD ID="masterPremis1"> <mdWrap MDTYPE="OTHER" OTHERMDTYPE="PREMIS" LABEL="PREMIS object metadata"> <xmlData> <premis:object> <premis:objectCharacteristics> <premis:fixity> <premis:messageDigestAlgorithm>SHA-1</premis:messageDigestAlgorithm> <premis:messageDigest><!--SHA-1 checksum (Required)--> </premis:messageDigest> <premis:messageDigestOriginator>Library of Congress</premis:messageDigestOriginator> </premis:fixity> <premis:size>1</premis:size><!--Size of the file in bytes.(Required)--> <premis:format> <premis:formatDesignation> <premis:formatName>image/tiff</premis:formatName> </premis:formatDesignation> </premis:format>

  5. What we do – example, continued <premis:significantProperties> <ndnp:exemptionSet> <ndnp:code>TEST1</ndnp:code> <ndnp:code>TEST2</ndnp:code> </ndnp:exemptionSet> </premis:significantProperties> </premis:objectCharacteristics> <premis:creatingApplication> <premis:creatingApplicationName><!--creatingApplicationName (optional)--></premis:creatingApplicationName> <premis:creatingApplicationVersion><!--creatingApplicationVersion (optional)--></premis:creatingApplicationVersion> <premis:dateCreatedByApplication>2004-11-22T00:00:00</premis:dateCreatedByApplication><!--dateCreatedByApplication (required for master)--> </premis:creatingApplication> </premis:object> </xmlData> </mdWrap> </techMD>

  6. What we do - related • MIX metadata for each image file • Enveloped XML digital signature for METS file • Modified PREMIS schema to omit some mandatory elements: • <objectIdentifier> • <objectCategory>

  7. How we do it • PREMIS is generated and inserted into METS by NDNP Validation Library • PREMIS is created by an XSLT transformation of representation information produced by JHOVE

  8. Lessons learned • Would prefer PREMIS schema to be more modular • Shift in (personal) philosophy: For technical/preservation metadata, less is more: • Collect metadata for immediate needs • Can’t guess what will be needed in the future • If metadata can be derived, then derive when necessary

  9. Lessons learned, continued • PREMIS as reference model rather than implementation model • Fixities stored in METS/PREMIS require custom tools to verify • Simpler approaches / common utilities more interoperable

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