https://en.wikipedia.org/wiki/X_Window_System
"X originated as part of Project Athena at Massachusetts Institute of Technology (MIT) in 1984.[3] The X protocol has been at version 11 (hence "X11") since September 1987."
"X originated as part of Project Athena at Massachusetts Institute of Technology (MIT) in 1984.[3] The X protocol has been at version 11 (hence "X11") since September 1987."
The CEE/7 standard was last revised in 1983 and is used by hundreds of millions of people every day.
ISO 8879 (SGML), which XML is a subset of, was ratified in 1986 already, making it closer to X11.
Also, you may want to check what XML 1.1 as opposed to 1.0 is about [1] - the vast vast majority of XML is 1.0 and has no reason to ever declare itself as 1.1 and in fact, every reason not to.
[1]: <http://www.ibiblio.org/xml/books/effectivexml/chapters/03.ht...>