anchor.diff:  		  schematool_info)
   	end)).
   
  +schema_keys() ->
  +    application:ensure_all_started(mnesia),
  +    atomic(
  +      mnesia:transaction(
  +	fun() ->
  +		mnesia:foldr(
  +		  fun(#schematool_info{datetime=Key}, Acc) ->
  +			  [Key|Acc]
  +		  end,
  +		  [],
  +		  schematool_info)
  +	end)).
  +
   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   %% Diff schema1 and schema2 (old vs new). Foundation for
   %% performing upgrade/downgrade/...
  
positive.code: atomic(Err) ->
      Err.
  
  %% Add a new schema definition to schematool_info. Note
  %% that this is just one part of migrating the schema.
  %%
  
negative.code: 
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  %% Collect tables that have been added, deleted or changed.
  %%
  %% Returns a list of actions that need to be performed to
  %% migrate from S0 to S1.
  %%
  %% Note: if N0 or N1 is just a single node, we do not have to
  %%  use the helper functions, just create/delete tables directly
  %%
  %% Note: interaction with add/delete nodes? 
  %% - (and changing fragments?)
  %%
  %% UNFINISHED
  %% - not sure if ordering is good
  