GNU name system
> A petname is a name that can be freely chosen by the user. This results in non-unique name-value mappings as www.bob.gnu to one user might be www.friend.gnu for someone else.<p>If names aren't fixed, how do you (for example) link from one website to another?  Or share a name with another user?<p>One of the advantages of the public DNS system, with unique, canonical names, is that the same name should mean the same thing to everyone.