code: private TermType getCommonDenominator(LanguageTag otherLanguageTag) {
          return langTag.getCommonDenominator(otherLanguageTag)
                  .map(newLangTag -> newLangTag.equals(langTag)
                          ? (TermType) this
                          : new LangDatatype(newLangTag, parentAncestry, typeFactory))
                  // Incompatible lang tags --> common denominator is xsd:string
                  .orElseGet(typeFactory::getXsdStringDatatype);
      }
docs: Common denominator between two lang strings