The information held in the directory consists of entries and alias entries, which is the information base, and of infrastructure information, which determines how the information base is structured. Directory Entries A directory entry is a set of attributes and their values . Every entry has an object class attribute, which specifies the kind of object the entry describes, and defines the set of attributes it contains.
Some attributes are mandatory and some are optional.
The schema defines the attributes that are mandatory and optional for an entry of a given object class. Directory information is hierarchical, with entries organized in a tree structure. Each entry has a parent entry and can have child entries. The top of the hierarchy is known as the root entry. A distinguished name is a sequence of attributes and values.