This class represents the address of a communications end-point.
It consists of a type that describes the communication mechanism
and an address contents determined by an RefAddr subclass.
For example, an address type could be "BSD Printer Address",
which specifies that it is an address to be used with the BSD printing
protocol. Its contents could be the machine name identifying the
location of the printer server that understands this protocol.
A RefAddr is contained within a Reference.
RefAddr is an abstract class. Concrete implementations of it
determine its synchronization properties.