CORBA24 — marshalling of null values unclear

Description: Instruction for marshalling of null values is missing (in

ptc/99-03-07). Issues include:

• The null_tag token is included in the grammar, but it's purpose is
  described nowhere. If this is the intended encoding of any null value,
  how are the typing semantics of values to be maintained? For example,
  which type-specific factory is to be used to create the null value to
  be
  passed to the servant? How are the truncation semantics to be
  preserved?
• There is a statement in 15.3.4.5 that "[t]he tag value 0 is reserved
  for future use". Does this refer to null_tag? (Note that there seems to
  be
  inconsistent use of "tag" within the text.) If so, how are null values
  to be marshalled? The grammar doesn't seem to allow for zero length
  value_data.

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