METS: Metadata Encoding and Transmission Standard

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METS Metadata Encoding and Transmission Standard

• Richard Gartner
• Oxford University Library Services
• rg_at_bodley.ox.ac.uk

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The digital library a status report

• Digitisation technology now well
  established and well-understood
• Standards for digitisation processes have
  settled down and are widely recognised
• Still a disparity in approaches to metadata -
  no MARC standard for digital library

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Approaches to metadata - some examples from Oxford

• Ad-hoc databases eg. Allegro
• SGML including-
• TEI alone
• TEI EAD
• Ad-hoc DTDs
• Proprietary databases eg Olive

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The lack of a standard what it mean for the
digital library

• poor cross-searching
• limited interchange facilities
• metadata tied to proprietary packages
• consequent obsolescence and costs of conversion

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What is needed?

• A standard for metadata content
  analogous to AACR2
• A standardised framework for holding and
  exchanging metadata analogous to the MARC
  record

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Three types of metadata(defined by DLF)

• Descriptive
• Administrative
• Structural

• Information about intellectual content
• (analogous to standard catalogue record)

• Information for handling, maintenance
• and archiving of object

• Description of internal structure of object

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METS Metadata Encoding and Transmission Standard

• Produced by Library of Congress Standards Office
  and Digital Library Federation
• Provides framework for holding all types of
  metadata for digital object
• Written in XML
• Does not prescribe content of metadata, but
  recommends a number of schemes for this

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Why XML?

• An ISO standard, not dependent on any given
  application
• Interchangeability with other applications
• Handles structural metadata easily
• Easy to integrate cataloguing information with
  text transcription, images etc.

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Features of a METS file

• All metadata (descriptive, administrative and
  structural) encoded in single document
• Each type is held in a separate section, linked
  by identifiers
• All metadata and external data (eg. images, text,
  video) is either referenced from METS file or can
  be held internally

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Descriptive and administrative metadata

• Descriptive and administrative metadata may
  be handled in two ways-
• embedding directly within the METS file
  within an ltmdWrapgt element (with any namespace)
• being held in an external file and
  referenced from the METS file using an
  ltmdRefgt element

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What to put in a METS file?

• METS does not prescribe the content
  (particularly the descriptive
  metadata) which it can contain

• However, the METS board does endorse some
  schemas as recommended-Descriptive
  Metadata
• Dublin Core
• MODS (Metadata Object Description Schema)
• MARCXML MARC 21 Schema (MARCXML) Administrative
  Metadata
• Schema for Technical Metadata for Text (NYU)
• Library of Congress Audio-Visual Prototyping
  Project
• NISO Technical Metadata for Digital Still Images
  
• Schema for Rights Declaration

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METS Profiles

• METS is very flexible in its application there
  are multiple ways of encoding everything-
• metadata and data can be embedded or
  referenced
• any scheme can be used for this metadata
• file inventory can be organised in multiple ways
  (by referenced object, by type of file
  etc)
• This all reduces interchangeability of METS
  records.

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METS Profiles

• This can be countered to some extent by METS
  Profiles-
• XML documents describing application of METS
  in a given project/institution
• follows METS Profile schema and each profile
  has to validate against it
• registered with central repository at Library of
  Congress
• But does not allow automated cross-mapping of
  METS files this has to be explored

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METS in action

• Oxford Digital Library-
• a collection of collections of material held in
  Oxford libraries
• METS files generated by automated webform-based
  cataloguing system
• descriptive metadata qualified Dublin Core
  following strict cataloguing guidelines
  (aimed to map to AACR2) moving to MODS being
  investigated
• METS files easily converted to formats of
  digital library systems (currently
  investigating Greenstone)

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Conclusions

• METS will undoubtedly be the central format for
  digital library metadata the MARC of the DL
  worldIssues to be addressed-
• standardization of metadata content and
  application (an AACR2 to MET's MARC)
• take-up by vendors lobbying by major bodies
• more tools needed for creation and exploitation
  of METS records
• critical mass

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Further information
www.loc.gov/standards/mets www.jisc.ac.uk/index.c
fm?nametechwatch_report_0205