anchor.diff:  handle_call({update_sub, SchemaId, SubId, Sub, Modifier}, _From, State) ->
       {Result, NewState} = update_sub(SchemaId, SubId, Sub, State, Modifier),
       {reply, Result, NewState};
  -handle_call({delete_sub, SchemaId, SubId, Modifier}, _From, State) ->
  -    {Result, NewState} = delete_sub(SchemaId, SubId, State, Modifier),
  +handle_call({delete_element, SchemaId, SubId}, _From, State) ->
  +    {Result, NewState} = delete_element(SchemaId, SubId, State),
  +    {reply, Result, NewState};
  +handle_call({delete_connection, SchemaId, SubId}, _From, State) ->
  +    {Result, NewState} = delete_connection(SchemaId, SubId, State),
       {reply, Result, NewState}.
   
   
  
positive.code: 
  read_schema_from_db(
          #schema{elements = Elements, connections = Connections} = Schema) ->
      io:format("~p~n", [Schema]),
      lists:foreach(fun notify_sub_creation/1, Elements),
      lists:foreach(fun notify_sub_creation/1, Connections),
      {continue, Schema}.
  
negative.code:     true|false).
  delete_element(SchemaId, ElementId) ->
      gen_server:call(?SERVER,
          {delete_element, SchemaId, ElementId}).
  
  %% Connections
  
  