X.500 was sold as a replacement for DNS and as a mechanism to allow applications to locate resources. X.500 was more flexible than DNS, and its directory service users have many more features and functions. The X.500 Directory Model is a distributed grouping of systems that cooperate in providing a logical database of information. Using this information, directory service users can access a global Directory Service to Directory subscribers. X.500 is also able to define the information model used in the Directory Service.
Directory services depend on namespaces.
Within the X.500 world, the namespace is presented as a logical hierarchical directory. X.500 deals with the structure of the entries in the namespace, and not the presentation of the information to the user. X.500 defines object classes for directories such as alias, country, locality, organization, organization unit, and person. This address would run the X.500 hierarchy presented in Figure 1. X.500 also has many limitations.