Is there a NID for URNs, which can be used for fully qualified class names?

Question

Is there a NID for URNs, which can be used for fully qualified class names?

I remember to have read something in the context of J2EE some years ago, but do not remember and did not find something using web search.

I found Is there a URN scheme for using domain names?, but this does not really match, because it contains additionally a mandatory date and resource identifier.