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NNNN-migration.md

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OCFL Community Extension NNNN: Migration

  • Extension Name: NNNN-migration
  • Authors: Jürgen Enge (Basel)
  • Minimum OCFL Version: 1.0
  • OCFL Community Extensions Version: 1.0
  • Obsoletes: n/a
  • Obsoleted by: n/a

Overview

Preservation management requires a migration strategy. This extension provides a way to migrate old file formats to new ones. It needs the NNNN-indexer extension to get Pronom IDs for the files. The migration is done by an external migration service. The migrated files are stored in a new version of the OCFL object.

Usage Scenario

If you have for example old PDF files, you can migrate them to PDF/A. This is a standard for archival PDF files. It is a good idea to migrate the files to PDF/A, because it is a more future-proof format.

Parameters

Summary

  • Name: storageType

    • Description: Location Type where the technical metadata is stored. Possible values are area, path or extension.
      • area: within an area defined by NNNN-content-subpath extension
      • path: directly within content folder
      • extension: within the extension subfolder
    • Type: string
    • Default:

  • Name: storageName

    • Description: Location within the specified Type
      • area: area name
      • path: subfolder within content folder
      • extension: subfolder within extension folder
    • Type: string
    • Default:

  • Name: compress

Caveat

The migration rules itself are not part of this extension. They are defined by the migration service.

Procedure (tbd.)

Every migrated entry whithin the OCFL Object Manifest is represented by a JSON line in a file called migration_<version>.jsonl[.gz|.br]. Since this file is immutable, every version of the ocfl object gets its own indexer file.

Examples

JSON Entry for a migrated pdf

{
	"path": "v2/content/data/=u007Eblä=u0020blubb=u005Bin=u005D/Modulhandbuch_MA_Gestaltung.pdf",
	"migration": {
		"source": "v1/content/data/=u007Eblä=u0020blubb=u005Bin=u005D/Modulhandbuch_MA_Gestaltung.pdf",
		"id": "PDFA#01"
	}
}

Result