From W3C Wiki
A universal name is a name which you can use nearly everywhere to mean the same thing. It's what you get when you see the value of GlobalNaming.
Of course names can only be used with perfect reliability inside a formal protocol. But the appearance of URIs in popular advertising demonstrated that they had become roughly universal names. Anywhere in the world, the string "http://www.w3.org" has roughly the same meaning.
It is not exactly clear what that string actually denotes, but that's okay. We don't need to share interpretations (in the model-theoretic sense) to use symbols to communicate. We just need to agree about the truth of statements using the symbol (and that only to the degree we agree about truth of statements in general).
please add arguments down here, in PPR:ThreadMode.