anchor.diff:  groups() ->
      [
         {interface, [parallel], 
  -         [lookup_by_rdf_id, lookup_by_lang_string]}
  +         [rdf_id, rdf_lang_string]}
      ].
   
   %%%----------------------------------------------------------------------------   
  
positive.code: ]).
  
  -export([
     lookup_by_rdf_id/1,
     lookup_by_lang_string/1
  ]).
  
  %%
  
negative.code:    } = eval("test(rdf:id, foaf:name) :- foaf:person(rdf:id, foaf:name, _, _), rdf:id = \"person:149\" . ").
  
  %%
  rdf_lang_string(_Config) ->
     #{
        '@type'     := test,
        'rdf:id'    := <<"person:137">>,
  