The simplist way to explain the differences between the DN and the RDN is to use the analogy with telephony, which also uses a tree structure for its numbering. Thus, for example, a local number is unique only within the area, but when used with the area code, the number is then unique. Finally, if the country code is also used, the final number uniquely identifies the particular phone line within the world.
For example, Company X's local number 255 2670 is distingished relative to London, the extended number 71-255 2670 is now distinguished relative to the UK, and the full number 44-71-255 2670 distinguishes Company X's telephone number uniquely throughout the world.
The DN is formed by using the sequence of RDNs as we traverse up the DIT until we reach the root.
The X.500 names may appear complex and cumbersome, however there is no reason why the complexity cannot be masked from the end user by the vendor's application software and make the name definition as natural and as easy-to-use as possible.
For example, defaults can be used so that all levels of the name need not be entered. When the name is not known directly, the application may also provide contextual help and guide the user into obtaining the name indirectly.
Another option is to use Aliases to help simplify a complex name, into a shorter, more simple name.