Best practice for updating and versioning of TDWG standard XML schemas

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Best practice for updating and versioning of TDWG
standard XML schemas

• Walter G. Berendsohn, Andrea Hahn, Anton
  Güntsch, Chuck Miller, Javier de la Torre, Markus
  Döring, Neil Thomson, Patricia Mergen, Renato De
  Giovanni, William Ulate, Wouter Addink

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Changes in ABCD versions

• Used versions of ABCD 1.2, 1.49, 2.0, 2.06,
  2.06a
• Bugfixing
• Elements without type,
• Misspellings of element or attribute names
• Duplication of elements
• Containers for unbound elements
• Additional substructures or simple elements
• Changes of types (restrictions, attribute
  addition, etc.)
• New complex types
• Clarification of semantics
• Change of semantics
• Renaming of elements or attributes

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Versions and extensions

• New namespace
• breaks all existing implementations
• xsany extension
• uncoordinated, non-standard
• No new namespace, version attribute
• may be dangerous
• clear definition of allowed changes needed
• must proceed in a coordinated manner
• Example GML

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ABCD versioning

• ABCD 2.06 adopted at TDWG 2005 in St. Petersburg
• Upgrade plan
• ABCD provides a provisional mechanism for
  extending the schema using xsany typed slots at
  the level of the unit, within site descriptions
  and within identification results.
• New version of ABCD to be released whenever a
  significant number of additions and changes have
  accumulated and/or structural changes are
  urgently needed.
• New version - new namespace for the new version
  of the ABCD schema.
• ABCD 2.6 has bugs and problems
• Interim version is needed

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TIP-sponsored ABCD workshop

• Interim version with same namespace ensuring full
  backward compatibility.
• Changes must not introduce changes which will
  break applications using previously approved
  versions
• The root element of the schema includes a version
  attribute indicating the schema version number.
• This number should agree with the namespace
  assigned to the schema.
• Minor changes are then indicated by letters. For
  example, the first interim version of ABCD 2.06
  should receive be identified as 2.06a.

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Backward compatibility

• is maintained when
• no elements or attributes are deleted
• (may be marked as deprecated)
• no elements or attributes are renamed
• (mark as deprecated and add new)
• the semantics of all elements are left unchanged
• (clarification of annotation text etc. is ok)
• type changes are restricted to assigning types to
  previously un-typed elements
• new elements are added

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ABCD 2.06 ? 2.06a

• Main changes
• defining types for several un-typed elements
• eliminating confusion concerning metadata
• adding a new extension slot at the dataset level
• addition of several elements for better
  compatibility to Darwin Core and HISPID
• See ABCD Wiki http//ww3.bgbm.org/abcddocs/

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Process?

• Review is needed! ?
• Process for new versions ?
• Process for interim versions?