Is there an official or de-facto common URN NID for private unregulated use?

Question

I would like to use URNs in a project of mine. And I am hardly willing to apply my humble project for official IANA registration but would like to keep from violating standards if possible. That's why I'd like to know if there is a standard (or de-facto common practice at least) NID to be placed instead of private in the following example:

urn:private:mycompany:myproject:mycollection:myresource

Answer 1

According to rfc2611 you can define any NID you like so long as it starts with "X-". Such namespaces are considered experimental:

No provision is made for avoiding collision of experimental NIDs; they are intended for use within internal or limited experimental contexts.

As there is no registration, no registration maintenance procedures are needed.