Since the Astroid system captures and stores the user inputs (rather than the results), it is able to maintain an exhaustive history of all edits made to your data with relatively low storage needs. Users are able to benefit from this information through the Plan History feature that is available within each treatment plan. The Plan History is a feature that allows the user to see and explore all the changes and modifications made to a plan. Each modification to a plan will result in a new Revision of the plan (note: in a complex plan there may be hundreds of revisions). If the user is not satisfied with the results of a modification they may go back to any of the previous revisions and restore it to the active instance (note: this will cause another Revision to be created for the reversion). Below is a walk through and more detailed explanation of this feature.

1. Open the General block from the Plan Overview and the History item can be seen at the bottom of this block
2. The summary of the latest revisions will appear in the right display pane
3. Expand the History details by clicking the small arrow (this is not mandatory)
   1. The number of plan revisions will be listed (In the above example there are 4 revisions)
4. The user can now review the various revision summaries
   1. Clicking the blue show link will expand that particular version of the plan and explain what was changed
   2. “op”: is the operation performed in this version that differs from the previous version (e.g. insert: an item was added)
   3. “path”: is the item in the treatment plan data that had the operation performed (e.g. points: a point geometry was changed)
   4. “val”: is the value of the data that was changed (see image below for the “val” of an added point)
5. If the user would like to return to this version they may do so by clicking the blue make active link
6. The user can close the expanded version by clicking the blue hide link