public boolean isField(final String fieldName) {
    if (fieldName != null) {
      return (KEYWORD_LIST.contains(fieldName.toUpperCase(Locale.US)) || fieldName.toUpperCase().startsWith(PROP_FIELD));
    }
    return false;
  }
Determines if specified string is a recognized field.

@param fieldName field name
@return true if recognized field.
olv-core/src/main/java/pl/otros/logview/accept/query/org/apache/log4j/spi/LoggingEventFieldResolver.java