title: storing revision changes of a message
body: <p>What algorithms and processes are involved in storing revision changes like stackoverflow and wikipedia do?</p>
  
  <p>Is only one copy of the message kept? And if so is it only the latest copy?  Then only changes to go back to the previous version(s) are stored from there?   (This would make for a faster display of the main message).
  Or are complete messages stored? And if so is the compare done between these on each display?</p>
  
  <p>What algorithms are best used to determine the exact changes in the message?  How is this data stored in a database?</p>
  
  <p>If anyone knows exactly what wikipedia or stackoverlfow does I'd love to know.</p>