Implementation of PREMIS in METS

1
Implementation of PREMIS in METS

• Rebecca Guenther
• Sr. Networking Standards Specialist, Library of
  Congress
• rgue_at_loc.gov
• PREMIS Implementation Fair
• San Francisco, CA
• October 7, 2009

2

• METS records the (possibly hierarchical)
  structure of digital objects, the names and
  locations of the files that comprise those
  objects, and the associated metadata
• A METS document may be a unit of storage (e.g.
  OAIS AIP) or a transmission format (e.g. OAIS SIP
  or DIP)
• METS is extensible and modular
• METS uses the XML Schema facility for combining
  vocabularies from different Namespaces
• The METS Editorial Board has endorsed PREMIS as
  an extension schema
• Many institutions trying to use PREMIS within the
  METS context

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Structure of a METS file
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OAIS, METS and PREMIS
ltMETSgt
described by
delimited by
Archival Information Package
Descriptive Information
Packaging Information
identifies
derived from
ltdmdSecgt
MODS MARCXML DC
Preservation Description Information
Content Information
further described by
ltfileGrpgt
ltamdSecgt
Reference Information
ltmdRefgt
Representation Information
Data Object
ltrightsMDgt
Context Information
metsRights premisrights
lttechMDgt
ltfilegt
ltstructMapgt
ltdigiProvMDgt ltsourceMDgt premisevent
Provenance Information
Semantics
Structure
described by
Fixity Information
lttechMDgt
premisobject
File formats
premisobject textMD MIX
Legend Black Arial OAIS Red Times New Roman
METS Primary Schema Blue Times New Roman Italics
Extension Schema
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METS extension schemas

• wrappers or sockets where elements from other
  schemas can be plugged in
• Provides extensibility
• Uses the XML Schema facility for combining
  vocabularies from different Namespaces
• Endorsed extension schemas
• Descriptive MODS, DC, MARCXML
• Technical metadata MIX (image) textMD (text)
• Preservation related PREMIS

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Why do we need guidelines for using PREMIS with
METS?

• Contents of each information package may vary
  depending on its function within a repository
• Need to determine how to include representation
  metadata and associate it with package components
• PREMIS data entities (objects, events, rights,
  agents) do not map perfectly to METS categories
  for representation metadata (techMD, digiProvMD,
  rightsMD, sourceMD)
• There are redundant elements between the two
  standards
• Both have extensibility mechanisms
• Flexibility of both standards requires
  implementation choices

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Development of Guidelines for Using PREMIS with
METS for Exchange

• PREMIS in METS Guidelines Working Group
• Consists of PREMIS and METS experts
• Focuses on the METS document as a mechanism of
  exchange of digital objects and their metadata
  (SIP or DIP)
• Facilitates communication when internal
  requirements and technical environments vary
• Tension between flexibility and being
  prescriptive to facilitate interoperability
• Consider usage scenarios
• If a SIP it may get unwrapped and stored in
  different structures
• If a DIP it is converted from internal structures
  to PREMIS
• A more liberal approach is possible for a SIP
  than a DIP
• Establishing guidelines, a METS profile, and
  examples
• http//www.loc.gov/standards/premis/guidelines-pr
  emismets.pdf

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Implementation issues in using PREMIS with METS

• Location of PREMIS metadata within METS documents
• Whether to record elements redundantly if they
  occur in both PREMIS and METS
• Relationship of different structural metadata
  mechanisms in PREMIS and METS
• How to record PREMIS Agent entities in METS
  documents
• Use of identifiers to link elements in PREMIS and
  METS
• How to record elements that are also part of a
  format specific technical metadata schema (e.g.
  MIX)

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Some recommendations from Guidelines

• METS sections
• Use Object in techMD or digiProvMD
• Use Event in digiProvMD
• Use Rights in rightsMD
• Use Agent in digiProvMD or rightsMD
• PREMIS Container -- use only if keeping all
  PREMIS metadata together. Do not use if
  separating PREMIS metadata into different amdSec
  subelements
• PREMIS and METS redundancies -- Choosing which
  options to use is an implementation decision,
  document in profile e.g. METS ltsizegt element
  attributes and subelements of ltobjectCharacteristi
  csgt in PREMIS

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Recommendations (cont.)

• Structural relationship elements -- use the METS
  structMap to record structural relationships, use
  PREMIS relationship elements to record
  preservation and derivation relationships and
  structural if desired
• ID/IDREF and PREMIS identifier elements -- use
  METS ID/IDREF mechanisms, best practices for
  using these ID/IDREF mechanisms apply
• Use PREMIS extensibility mechanism for format
  specific technical metadata
• Document decisions in METS profiles

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• ltfileSecgtltfileGrpgt
• ltfile ID"FID1" SIZE"184302" ADMID"TMD1PREMIS
  TMD1MIX DP1EVENT DP1AGENT CHECKSUM"4638bc65c5b97
  15557d09ad373eefd147382ecbf" CHECKSUMTYPE"SHA-1"gt
  
• ltFLocat LOCTYPE"OTHER" xlinkhref"BXF22.JPG" /gt
• lt/filegtlt/fileGrpgtlt/fileSecgt
• lttechMD ID"TMD1PREMIS"gt
• ltmdWrap MDTYPE"PREMIS"gt
• ltxmlDatagt ltpremisobject gt
  ltobjectCharacteristicsgt ltfixitygt
  ltmessageDigestAlgorithmgtSHA-1 lt/messageDigestAlgor
  ithmgt ltmessageDigestgt4638bc65c5b9715557d09
  ad373eefd147382ecbf 
• lt/messageDigestgt
  ltmessageDigestOriginatorgtEchoDep/me
  ssageDigestOriginatorgt lt/fixitygt
  ltsizegt184302lt/sizegt lt/objectCharacteristicsgt
• Elements defined in both METS and PREMIS
• METS Checksum, Checksumtype
• attribute of ltfilegt
• not repeatable
• PREMIS fixity
• also includes messageDigestOriginator
• allows multiples

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• ltfileSecgtltfileGrpgt
• ltfile ID"FID1" ADMID"TMD1PREMIS DP1EVENT
  DP1AGENT MIMETYPE"image/jpeg"
• ltFLocat LOCTYPE"OTHER" xlinkhref"BXF22.JPG"/gt
• lt/filegtlt/fileGrpgtlt/fileSecgt
• lttechMD ID"TMD1PREMIS
• ltmdWrap MDTYPE"PREMIS"gt
• ltxmlDatagt
• ltpremisobjectgt
• ltobjectCharacteristicsgt
• ltformatgt
• ltformatDesignationgt
• ltformatNamegtimage/jpeglt/formatNam
  egt
•   ltformatVersiongt1.02 lt/formatVersi
  ongt
• lt/formatDesignationgtlt/formatgt
• lt/objectCharacteristicsgt
• Elements defined both in METS and PREMIS
• METS MIMETYPE
• attribute of ltfilegt

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• ltfileSecgt ltfileGrpgt
• ltfile ID"FID1" ADMID"TMD1PREMIS TMD1MIX
  DP1EVENT DP1AGENT"gt
• lttechMD ID"TMD1PREMIS"gt
• ltlinkingEventIdentifiergt
• ltlinkingEventIdentifierTypegtECHODEP Hub
  Event
• lt/linkingEventIdentifierTypegt
• ltlinkingEventIdentifierValuegtecho12345lt/linki
  ngEventIdentifierValuegt
• lt/linkingEventIdentifiergt
• ltdigiprovMD ID"DP1EVENT"gt
•   ltpremiseventgt
• lteventIdentifiergt
• lteventIdentifierTypegtECHODEP Hub Eventlt/e
  ventIdentifierTypegt
• lteventIdentifierValuegtecho12345 lt/eventId
  entifierValuegt
• lt/eventIdentifiergt
• lteventTypegtingestionlt/eventTypegt
• lteventDateTimegt2006-05-02T151253 lt/eventD
  ateTimegtlt/eventgt
• Elements defined both in METS and PREMIS
• METS ID/Idref used to associate metadata in
  different sections and for different files

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• ltstructMap TYPEphysicalgt
• ltdiv ORDER"1" TYPE"text"gt
• ltfptr FILEID"FID9"/gt
• ltdiv ORDER"1" TYPE"page" LABEL" Page
  1"gt
• ltfptr FILEID"FID1"/gtlt/metsdivgt
• ltdiv ORDER"2" TYPE"page" LABEL" Page
  2"gt
• ltfptr FILEID"FID2"/gtlt/metsdivgt
• lt/divgt
• ltrelationshipgt
• ltrelationshipTypegtstructurallt/relationshipTypegt
  
• ltrelationshipSubTypegtis sibling of
  lt/relationshipSubTypegt
• ltrelatedObjectIdentificationgt
• ltrelatedObjectIdentifierTypegtUCBlt/relatedObje
  ctIdentifierTypegt
• ltrelatedObjectIdentifierValuegtFID2lt/relatedOb
  jectIdentifierValuegt
• ltrelatedObjectSequencegt1lt/relatedObjectSequen
  cegt
• Elements defined both in METS and PREMIS
• METS structMap

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Some METS profiles with PREMIS

• UCSD simple and complex object
• UC Berkeley
• ECHO Dep Generic METS Profile for Preservation
  and Digital Repository Interoperability
• LC Profile for Recorded Events
• Australian METS Profile
• TIPR
• many others

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Additional changes to Guidelines

• Make extensibility mechanism consistent with METS
• significantPropertiesExtension
• objectCharacteristicsExtension
• creatingApplicationExtension
• environmentExtension
• signatureInformationExtension
• eventOutcomeDetailExtension
• rightsExtension

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Additional changes to Guidelines (cont.)

• Add the same elements and attributes as in METS
  to PREMIS extension elements in schema and data
  dictionary
• mdRef, mdWrap
• binData, xmlData
• Attributes ID, LABEL, MDTYPE, MIMETYPE, SIZE,
  CREATED, CHECKSUM, CHECKSUMTYPE
• Allow URI or string for MDTYPE
• Add use cases/examples to illustrate choices made
• Clarify structural relationships

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Implementing an Exchange Standard

• PREMIS Implementation Tool
• Some tools documented on the PREMIS website
  http//www.loc.gov/standards/premis/tools_for_prem
  is.php
• PiM tool developed by Florida Center for Library
  Automation
• Further work to generate metadata from digital
  files in PREMIS elements