[omniORB] Extending a union by a member - is a mismatch btw. server and client IDL allowed?

[Martin B.]

Our CORBA API currently has an interface like:

     module XYZ {
       ...
       enum DataType {
         FloatingPointT,
         IntegerT
       };

       // v 1.1
       union Value switch (DataType) {
         FloatingPointT : double dv;
         IntegerT : long iv;
       };

       interface ... {
         Value GetValue(....);
       ...

We now would like to extend this interface to allow for string values in 
addition to the two existing types:

       // v 1.2
       enum DataType {
         FloatingPointT,
         IntegerT,
         StringT
       };

       union Value switch (DataType) {
         FloatingPointT : double dv;
         IntegerT : long iv;
         StringT: string;
       };

and keep the interface the same otherwise.

Is a client compiled with v1-1.idl supposed to be able to talk to a 
server compiled with v1-2.idl -- where the definition of the union (and 
the enum) differ but are a pure addition to the existing interface?

Can a client correctly invoke GetValue() as long as this function 
doesn't return a unknown datatype?

Is this covered by the CORBA spec at all?

Note: It *does* indeed work when I test it with omniORB 4.1.4 (both 
client and server) but that doesn't tell me whether it'll work with all 
possible client ORBs!

Thanks for any pointers!

cheers,
Martin