On Tue, Jan 31, 2012 at 7:22 PM, Matt Corallo <bitcoin-list@bluematt.me> wrote:

All that said, I dont think its an ideal solution, depending on the
names of variables to provide information is ugly. If anyone has a
better idea on how to do backward compatibility, please suggest it.

I like the mustimplement: idea, though I'd recommend a shorter (abbreviated) prefix, to keep URL sizes small for QR codes and such,

Wladimir