OCL2_ — OclUndefined = OclUndefine ?

Perhaps it makes sense to explicitly mention whether OclUndefined = OclUndefined results in OclUndefined (or true)? The SQL equivalent seems to cause a lot of confusion, especially since in C "NULL == NULL" resturns true. For example, the above expression would not work with excluding(OclUndefined), given (OclUndefined=OclUndefined).isOclUndefined().....

Technically, no change is necessary because the OclAny definition of the = operation, together with the definition of the singleton values null and invalid, is sufficient. However, being more explicit is helpful, especially as the there is no oclIsXyz() operation testing for void but not invalid.