2.2.5.2 XML Streams
The message MUST have the PidTagRoamingDatatypes property (section 2.2.2.1) set. The value of the property MUST be a bitmask that includes 0x00000002.
The message MUST have the PidTagRoamingXmlStream property (section 2.2.2.3) set. The value of the property MUST be a PtypBinary stream that contains a Unicode XML document that is using the UTF8 encoding.
In addition to the XSDs that are specified in sections 2.2.5.2.1 through 2.2.5.2.3, the XML document MUST conform to the limitations specified in section 2.2.3.
If the application encounters unknown XML elements while parsing the document, it SHOULD preserve those elements without modification and include them whenever it makes modifications to the parts of the document that it understands.