TWiki has "Soft security" - anyone can change anything, but changes are logged. There is a complete audit trail:
Version
Date of last revision
Person who made change
is recorded. At the footer of each topic one can click on previous versions. One can also see the differences between revisions by clicking on the > sign located between revisions of a topic.
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-- TWiki:Main.PaulineCheung - 30 Jan 2005