LDAP

http://docs.oracle.com/javase/jndi/tutorial/ldap/index.html

LDAP
The Lightweight Directory Access Protocol (LDAP) is a network protocol for accessing directories. It is based on the X.500

X.500
The X.500 directory service is a global directory service. Its components cooperate to manage information about objects such as countries, organizations, people, machines, and so on in a worldwide scope. It provides the capability to look up information by name (a white-pages service) and to browse and search for information (a yellow-pages service).

The information is held in a directory information base (DIB). Entries in the DIB are arranged in a tree structure called the directory information tree (DIT). Each entry is a named object and consists of a set of attributes. Each attribute has a defined attribute type and one or more values. The directory schema defines the mandatory and optional attributes for each class of object (called the object class). Each named object may have one or more object classes associated with it.

The X.500 namespace is hierarchical. An entry is unambiguously identified by a distinguished name (DN). A distinguished name is the concatenation of selected attributes from each entry, called the relative distinguished name (RDN), in the tree along a path leading from the root down to the named entry.