DBException to extend from XMLDBException?

[Vadim Gritsenko]

I've noticed in FaultCodes (not last version, but previous one) that the 
reason for conversion between DBException and XMLDBException was that 
XMLDBException was missing cause exception.

Now, XMLDBException has everything:
   private Throwable cause;
   public int errorCode;
   public int vendorErrorCode;
And by extending DBException from XMLDBException, exception handling can 
be simplified (less catch/rethrows).

What's your opinion?
Vadim