Certain programs look for /dev/dvd by default to find DVDs. When I first boot my computer without a DVD inserted, /dev/dvd exists and points to the correct place (/dev/sr0). However, when I insert a DVD, /dev/dvd disappears. I'd like it to stick around so I don't have to navigate to /dev/sr0 in programs that are looking for DVDs. How do I ensure that the /dev/dvd symlink exists and points to the right place?

It looks like I can add something to /etc/udev/rules.d/70-persistent-cd.rules. This site gives a couple of examples, but the 70-persistent-cd.rules file says "add the ENV{GENERATED}=1 flag to your own rules", which isn't part of the examples. The man 7 udev page is impenetrable to me, and I'm not convinced the linked page gives 100% of the information I need.

So, what can I do on a modern, Ubuntu 12.04 (or later) system to make /dev/dvd always exist and point to the right device?

EDIT: Is it as simple as adding ENV{GENERATED}=1 to the rules in the linked page, something like this:

SUBSYSTEM=="block", KERNEL=="sr0", SYMLINK+="dvd", GROUP="cdrom", ENV{GENERATED}=1

Is that the right information for modern Ubuntu? What is ENV{GENERATED} doing there, when it wasn't generated, but hand-written?