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changes.mady.by.user Andrew Woods

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changes.mady.by.user Osman Din

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Excerpt
Within Fedora 4, snapshots of the current state of an object 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 for easy export of the entire history or other useful actionspossible use cases.

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 allows allow easy retrieval of that version.

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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 the version historythis feature.

Possible strategies include:

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

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From the HTML view (or by issuing HTTP GET methods in via an HTTP client program) you can get the version history of a node by appending "/fcr:versions" to it's base URL.  Each version will be listed, either using with the version label as the title, or for versions without labels, the modification date will be used instead. 

Previewing historic properties

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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 and certain properties have been stored in different property names (mixin types, uuid) but you can export that snapshot or view any contentview or export it.

Reverting to a previous version

If you wish to restore an object to a previous version, you may do so using the REST API, or  or even the HTML view.  In the HTML view of a historic version, a button exists on the right hand side saying "Revert to this Version" exists, that when clicked restores the object (and possibly the subgraphsub-graph) to the version viewed.

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 new version explicitly if you want to create a new version that records the revert.