Yes, and they work but are too heavy a solution. Try approaching them and saying:
Hi! I would like to reserve two billion DOIs :)
yea, NOPE!
There are lighter schemes out there but none are household names yet.
yea, NOPE!
There are lighter schemes out there but none are household names yet.
If you've already registered a prefix with them (say it's 10.8888), then you have an essentially unlimited namespace of possible suffixes for forming DOIs. Representing two billion DOIs requires only 6 suffix digits in base 36.
What exactly is so difficult about this?