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