A means whereby, something which has been '''Done''', can be '''Un Done'''.

The MementoPattern described in the DesignPatterns book can be used to
implement undo mechanisms in software.

The CommandPattern in the DesignPatterns book is an even stronger implementation strategy in many cases.

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On this wiki in particular,
mis-guided edits can be "undone" by clicking "Edit"
and then "EditCopy".
See MoreAboutBackupCopies for details.

If there are TwoMinorEdits (such as on WikiFarms), the data is lost. ( Or is it ? )