n RELATIVE The relative method is a function that returns a 0 for equals, a negative
value for less than, and a positive value for greater than.
n MAP The map method uses a function that takes a single argument of the UDT type
and returns a predefined data type. Comparing two UDTs is achieved by comparing the
two map values associated with them.
n STATE The state method compares the attributes of the operands to determine an order.
CAST functions can also be defined to provide user-specified conversion functions between
different UDTs. In a subsequent version of the standard it may also be possible to override
some of the built-in operators.