Regularly when OOXML is discussed it is referred to as a XML that can contain binary blob. In the past the Office 2003 XML formats did indeed contains embedded binary date within the file. This of course due to the fact that this format consisted of a single XML file. With OOXML a big change is now that the binary embedded formats are put in the package as separate files.
So is binary data within XML a thing of the past.
No, not really, you can still find it here:
Yes, right in the middle of the Opendocument.
It is called the office:binary-data element.
It refers to a base64 binary encoded element within the XML.
So why does no one ever mention that ODF can contain binary data within the XML ?