What would be a valid D-Bus interface name for a project without domain?

[Lawrence D'Oliveiro]

On Wed, 24 Jan 2018 10:16:52 +0000, Emmanuele Bassi wrote:

> On 23 January 2018 at 21:01, Lawrence D'Oliveiro
> <ldo at geek-central.gen.nz> wrote:
>
>> How about assigning a subdomain of org.freedesktop?
>> org.freedesktop.dbus, say.  
> 
> The org.freedesktop.* namespace should be reserved for FreeDesktop.Org
> projects, not for random projects. It's especially important because
> DBus interfaces reside on the org.freedesktop.* namespace.

Yes, naturally that would apply to org.freedesktop.dbus (which is
already used for interface names and bus names as part of the D-Bus
spec, which I forgot). But what about a subdomain of that?
“org.freedesktop.dbus.random.«whatever»”, say, or
“org.freedesktop.dbus.unassigned.«whatever»”.

Or how about the good old “X-” prefix?
“org.freedesktop.x-dbus.«whatever»”?