ADVANTAGE OF STRUCTURAL MODEL

Absolute naming implies that the (complete) names are assigned with respect to a universal reference point. The advantage of absolute naming is that a name thus assigned can be universally interpreted with respect to the universal reference point. The Internet naming convention provides absolute naming with the naming universe as its universal reference point.For relative naming, an entity is named depending upon the positionof the naming entity relative to that of the named entity. A set ofhosts running the "unix" operating system exchange mail using a method called "uucp". The naming convention employed by uucp is an example of relative naming. The mail recipient is typically named by a source route identifying a chain of locally known hosts linking thesender's host to the recipient's. A destination name can be, for example, "alpha!beta!gamma!john", where "alpha" is presumably known to the originating host, "beta" is known to "alpha", and so on. The uucp mail system has demonstrated many of the problems inherent to relative naming. When the host names are only locally interpretable, routing optimization becomes impossible. A reply message may have to traverse the reverse route to the original sender in order to be forwarded to other parties. Furthermore, if a message is forwarded by one of the original recipients or passed on as the text of another message, the frame of reference of the relative source route can be completely lost. Such relative naming schemes have severe problems for many of the uses that we depend upon in the ARPA Internet community.To allow interoperation with a different naming convention, the names assigned by a foreign naming convention need to be accommodated. Given the autonomous nature of domains, a foreign naming environment may be incorporated as a domain anywhere in the hierarchy. Within the naming universe, the name service for a domain is provided within that domain. Thus, a foreign naming convention can be independent of the Internet naming convention. What is implied here is that no standard convention for naming needs to be imposed to allow interoperations among heterogeneous naming environments. For example: There might be a naming convention, say, in the FOO world, something like "%%". Communications with an entity in that environment can be achieved from the Internet community by simply appending ".FOO" on the end of the name in that foreign convention.

Communicating with a complex subdomain is another case which can be treated as interoperation. A complex subdomain is a domain with complex internal naming structure presumably unknown to the outside world (or the outside world does not care to be concerned with its complexity). For the mail system application, the names embedded in the message text are often used by the destination for such purpose as to reply to the original message. Thus, the embedded names may need to be converted for the benefit of the name server in the destination environment.