code: public ICalDataType getValue() {
  		String value = first(VALUE);
  		return (value == null) ? null : ICalDataType.get(value);
  	}
docs: <p>
  Gets the VALUE parameter value.
  </p>
  <p>
  This parameter defines the data type of the property value (for example,
  "date" if the property value is a date without a time component). It is
  used if the property accepts multiple values that have different data
  types.
  </p>
  @return the data type or null if not set
  @see <a href="http://tools.ietf.org/html/rfc5545#page-29">RFC 5545
  p.29-50</a>