I've dabbled in serial communications for many years now, starting with Signetics 2650 and then moving to more advanced serial routines all written in assembler for the Zilog Z80 way back in the eighties, so, when I read what hewi writes on serial communications:
simplest form: we fire a one into space and don't care about the rest
I must say, I am lost as to what is the meaning of such a statement. Do I use a canon to fire a large cut-out of the number '1' into space, pointed to say, little Pluto ? And, should I not care about the rest, the rest of what ?
Maybe I shouldn't start on:
most complex form: time, voltage and frequency multiplexing signals are sent through all sorts of possible media, using all sorts of protocols, the signals are error checked back and forth, in and out, into four dimensions
Hewi, can I suggest you state clearly of what you mean, rather than saying 'all sorts', be specific.
If you say 'all sorts of protocols', that doesn't give any information at all.
The OSI model has been clearly defined many years ago now, though I am unsure exactly how your reference to it relates, maybe you could explain more clearly what you mean ?
Maybe a point list detailing benefits and applications would help also.
I'll get back to writing my own serial protocols again 
Paul - VK7KPA