Source : Free On-Line Dictionary of Computing

directory service
     
         A structured repository of information
        on people and resources within an organisation, facilitating
        management and communication.
     
        On a {LAN} or {WAN} the directory service identifies all
        aspects of the {network} including users, software, hardware,
        and the various rights and policies assigned to each.  As a
        result applications can access information without knowing
        where a particular resource is physically located, and users
        interact oblivious to the network {topology} and {protocols}.
     
        To allow {heterogeneous networks} to share directory
        information the {ITU} proposed a common structure called
        {X.500}.  However, its complexity and lack of seamless
        {Internet} support led to the development of {Lightweight
        Directory Access Protocol} (LDAP) which has continued to
        evolve under the aegis of the {IETF}.  Despite its name {LDAP}
        is too closely linked to {X.500} to be "lightweight".
     
        {LDAP} was adopted by several companies such as {Netscape
        Communications Corporation} (Netscape Directory Server) and
        has become a {de facto standard} for directory services.
        Other LDAP compatible offerings include {Novell, Inc.}'s
        {Novell Directory Services} (NDS) and {Microsoft
        Corporation}'s {Active Directory}.  The Netscape and Novell
        products are available for {Windows NT} and {Unix}
        {platforms}.  {Novell Directory Services} also run on Novell
        platforms. {Microsoft Corporation}'s {Active Directory} is an
        integral part of {Microsoft's Windows 2000} and although it
        can interface with directory services running on other systems
        it is not available for other platforms.
     
        (2001-01-02)