[rwaldron]

> behaviour is well defined.

True, and we could go one step further: it's unambiguously defined, with invariant rules that can be used to prove a conformant implementation.

[heavenlyblue]

Yet we still struggle with making sure we've got all of the tools that could check the mistakes I have accidentally made before I had shipped the code.

XMPP had been defined as formally: where have we ended up with it now?