Editing X.500 (section)

==X.500 data models==
The primary concept of X.500 is that there is a single [[Directory Information Tree]] (DIT), a hierarchical organization of entries which are distributed across one or more servers, called [[Directory System Agent]]s (DSA).  An entry consists of a set of attributes, each attribute with one or more values.  Each entry has a unique [[Distinguished Name]], formed by combining its [[Relative Distinguished Name]] (RDN), one or more attributes of the entry itself, and the RDNs of each of the superior entries up to the root of the DIT. As LDAP implements a very similar data model to that of X.500, there is further description of the data model in the article on [[Lightweight Directory Access Protocol|LDAP]].

[[X.520]] and [[X.521]] together provide a definition of a set of attributes and object classes to be used for representing people and organizations as entries in the DIT.  They are one of the most widely deployed [[white pages schema]].

[[X.509]], the portion of the standard providing for an authentication framework, is now also widely used outside of the X.500 directory protocols.  It specifies a standard format for public-key certificates.