anchor.diff:              io:format("Using difference types for powerset generation: ~p~n", [DifferenceTypes]),
   
               %% Use message trace.
  -            FilteredTraceLines = filter_trace_lines(TraceLines),
  +            FilteredTraceLines = filter_trace_lines(TraceLines, BackgroundAnnotations),
   
               %% Generate powerset using *only* the new messages.
  -            FilteredDifferenceTraceLines = filter_trace_lines(DifferenceTraceLines),
  +            FilteredDifferenceTraceLines = filter_trace_lines(DifferenceTraceLines, BackgroundAnnotations),
               {Time, L} = timer:tc(fun() -> powerset(FilteredDifferenceTraceLines) end),
   
               % io:format("FilteredDifferenceTraceLines: ~p~n", [FilteredDifferenceTraceLines]),
  
positive.code:                         ok
                  end,
  
                  ClassifySchedule = classify_schedule(3, Annotations, PrefixMessageTypes, OmittedMessageTypes, ConditionalMessageTypes),
                  % io:format("Classification: ~p~n", [dict:to_list(ClassifySchedule)]),
  
                  case os:getenv("PRELOAD_SCHEDULES") of 
                      false ->
                          case GenIteration0 rem 10000 == 0 of 
                              true ->
                                  io:format(".", []);
  
negative.code: 
                  case InterpositionType of 
                      forward_message ->
                          MessageType = message_type(Message),
                          case lists:member(element(2, MessageType), BackgroundAnnotations) of 
                              true ->
                                  false;
                              false ->
                                  true
                          end;
                      _ -> 
                          false
                  end;
  