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changes.mady.by.user Osman Din

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changes.mady.by.user Michael Durbin

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Excerpt
Within Fedora 4, snapshots of the current state of an object a resource may be saved into the version history.  The properties or content of a node saved in these versions may be accessed later to serve as a historical record of the object.  Future feature development may allow easy export of the entire history or other possible use casesRDF for historic version shapshots may be browsed and old non-RDF content may be downloaded.  Furthermore, an object or subgraph may be reverted to the state that it existed in a historic version.

Creating versions

When you wish to save a snapshot of the current version of a node to the version history you can use the REST API.  When saving these versions you must provide a label that both serves to easily differentiate a version from another and allow easy retrieval of that version.

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Note
titleDuplicate Version Labels
If a second version is created with the same label as a previous version, that label is quietly reassigned to the most recent version tagged a resource has a version with a given label, you may not create another version with that label.  If you later delete a labeled version, you may then create a new version with that label.
Tip

Version creation is a relatively costly operation.  With the ability to create versions whenever you wish, you can develop workflows that maximize the utility of this feature.

Possible strategies include:

  • For batch operations, only create version checkpoints once nodes have been ingested, verified and tested.
  • For small (but high-level) data such as the descriptive metadata created by subject experts, set a versioning policy to store every modification, thereby capturing the entirety of the curatorial endeavor.
  • Create snapshot versions that correspond to released versions of content (i.e., version X of a shared dataset, controlled vocabulary or collection)

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By clicking on the label of a version in the version listing you will be taken to the stored version of that resource.  Because it's part of the historic record, you cannot edit it, but you can view or export itit, download non RDF-content or revert the resource or subraph to that version.

Reverting to a previous version

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Info

When restoring an old version, two operations occur:

  1. Immediately before restoring the old version, a version snapshot is made to reflect the current state of the object.  This version will not have a version label.
  2. The current state of the resource will be updated to match the version being restored – but a new version will not be created.  You can create a version explicitly if you want to create a version that records the revert.

Deleting a previous version

If you wish to remove historic version snapshots you may do so either using the REST API or the HTML view of the historic version. You may not, however, delete the most recent version snapshot