The XML 1.0 parser may or may not accept documents that have a different version number than 1.0. The behavior of your XML parser depends on which version of the XML 1.0 recommendation is appropriate.
First issues
W3C XML Recommendations 1 and 2 say:
"1.0" ; "1.0" , .
...
, , , .
version XML
[26] VersionNum ::= ([a-zA-Z0-9_.:] | '-')+
ref: http://www.w3.org/TR/1998/REC-xml-19980210#sec-prolog-dtd
3- . , , version 1.0
[26] VersionNum ::= '1.0'
, XML 1.0 .
ref: http://www.w3.org/XML/xml-V10-2e-errata#E38
5- , .
, VersionNum '1.x', XML 1.0 , '1.0'.
. XML 1.0 , 1.x, "1.0" , 1.0. , XML 1.0 1.x , 1.0.
version 1.x
[26] VersionNum ::= '1.' [0-9]+
ref: http://www.w3.org/XML/xml-V10-4e-errata#E10
1.0 ( XML 1.0) , . , , , XML 1.1 ( XML 1.0 5th Ed., - XML 1.1).