code: public static String getDatatypeIriFromJsonDatatype(String jsonDatatype) {
  		switch (jsonDatatype) {
  		case JSON_DT_ITEM:
  			return DT_ITEM;
  		case JSON_DT_PROPERTY:
  			return DT_PROPERTY;
  		case JSON_DT_GLOBE_COORDINATES:
  			return DT_GLOBE_COORDINATES;
  		case JSON_DT_URL:
  			return DT_URL;
  		case JSON_DT_COMMONS_MEDIA:
  			return DT_COMMONS_MEDIA;
  		case JSON_DT_TIME:
  			return DT_TIME;
  		case JSON_DT_QUANTITY:
  			return DT_QUANTITY;
  		case JSON_DT_STRING:
  			return DT_STRING;
  		case JSON_DT_MONOLINGUAL_TEXT:
  			return DT_MONOLINGUAL_TEXT;
  		default:
  			if(!JSON_DATATYPE_PATTERN.matcher(jsonDatatype).matches()) {
  				throw new IllegalArgumentException("Invalid JSON datatype \"" + jsonDatatype + "\"");
  			}
  
  			String[] parts = jsonDatatype.split("-");
  			for(int i = 0; i < parts.length; i++) {
  				parts[i] = StringUtils.capitalize(parts[i]);
  			}
  			return "http://wikiba.se/ontology#" + StringUtils.join(parts);
  		}
  	}
docs: Returns the WDTK datatype IRI for the property datatype as represented by
  the given JSON datatype string.
  
  @param jsonDatatype
  the JSON datatype string; case-sensitive
  @throws IllegalArgumentException
  if the given datatype string is not known