general undo methods?

[Cubist at aol.com]

   To a zeroeth approximation, use a frontscript or backscript to keep a 
realtime-updated record of *everything* the user does (for whatever value of 
"everything" you deem relevant or comfortable or etc). This record should, in each 
specific item, include enough information that you can reconstruct what 
changed in each item. For instance:

  delta 000111,graphic "fred" of card "george" of stack "harry",points 
changed from "yada yada" to "aday aday"

   It seems to me that something like UmbrellaMan might be a suitable 
foundation on which to start building a generalized Undo.