code: private static String mapWotanTagSetToNAF(final String postag) {
      if (postag.equalsIgnoreCase("ADV")) {
        return "A"; // adverb
      } else if (postag.equalsIgnoreCase("CONJ")
          || postag.equalsIgnoreCase("SCONJ")) {
        return "C"; // conjunction
      } else if (postag.equalsIgnoreCase("Art")) {
        return "D"; // det predeterminer
      } else if (postag.equalsIgnoreCase("ADJ")) {
        return "G"; // adjective
      } else if (postag.equalsIgnoreCase("N")) {
        return "N"; // common noun
      } else if (postag.equalsIgnoreCase("PROPN")) {
        return "R"; // proper noun
      } else if (postag.equalsIgnoreCase("Prep")) {
        return "P"; // preposition
      } else if (postag.equalsIgnoreCase("PRON")) {
        return "Q"; // pronoun
      } else if (postag.startsWith("V")) {
        return "V"; // verb
      } else {
        return "O"; // other
      }
    }
docs: Mapping between Wotan (Alpino) tagset and NAF.
  
  @param postag
  the postag
  @return the mapping to NAF pos tagset