XMLSerialize: version and explicit XML declaration

Hi,

I'm working on the flags VERSION (X076), INCLUDING XMLDECLARATION, and
EXCLUDING XMLDECLARATION (X078) for XMLSerialize, and I have a question
for SQL/XML experts on the list.

Is there any validation mechanism for VERSION <character string
literal>? The SQL/XML spec says

"The <character string literal> immediately contained in <XML serialize
version> shall be '1.0' or '1.1', or it shall identify some successor to
XML 1.0 and XML 1.1."

I was wondering if a validation here would make any sense, since
XMLSerialize is only supposed to print a string --- not to mention that
validating "some successor to XML 1.0 and XML 1.1" can be challenging :)
But again, printing an "invalid" XML string also doesn't seem very nice.

The oracle implementation accepts pretty much anything:

SQL> SELECT xmlserialize(DOCUMENT xmltype('<foo><bar>42</bar></foo>')
VERSION 'foo') AS xml FROM dual;

XML
--------------------------------------------------------------------------------
<?xml version="foo"?>
<foo>
  <bar>42</bar>
</foo>

In db2, anything other than '1.0' raises an error:

db2 => SELECT XMLSERIALIZE(CONTENT XMLELEMENT(NAME "db2",service_level)
AS varchar(100) VERSION '1.0' INCLUDING XMLDECLARATION) FROM
sysibmadm.env_inst_info;

1                                                                                                 
 
----------------------------------------------------------------------------------------------------
<?xml version="1.0" encoding="UTF-8"?><db2>DB2
v11.5.9.0</db2>                                      

  1 record(s) selected.

db2 => SELECT XMLSERIALIZE(CONTENT XMLELEMENT(NAME "db2",service_level)
AS varchar(100) VERSION '1.1' INCLUDING XMLDECLARATION) FROM
sysibmadm.env_inst_info;
SQL0171N  The statement was not processed because the data type, length or
value of the argument for the parameter in position "2" of routine
"XMLSERIALIZE" is incorrect. Parameter name: "".  SQLSTATE=42815

Any thoughts on how we should approach this feature?

Thanks!

Best, Jim