Appendix C. Introduction to ADSI

In February 1997, Microsoft released a set of generic interfaces, called the Active Directory Service Interfaces (ADSI), to access and manipulate different directory services. ADSI is a collection of classes and methods that allows developers using any language that supports the component object model (COM) to access and manipulate objects on workstations and servers or in a directory service, such as Active Directory. Contrary to its name, it was written to be generic and extensible rather than specific to Active Directory. This means that developers can write code to access objects on various directory servers without the need to know vendor-specific library routines or APIs. ADSI is also extensible so developers of other directory services can write the underlying Dynamic Link Library (DLL) code that will allow ADSI to interact with their systems. This is possible because Microsoft publishes the specifications that a Directory Service Provider (code that implements the ADSI specification for a particular directory service) must meet to work correctly with ADSI. This means that whenever you call an ADSI procedure or reference any object via ADSI against a valid provider, you can feel confident that the procedure will perform according to ADSI's formal documentation no matter what the provider is. While there are several directory service provider-specific extensions, ADSI also supports Lightweight Directory Access Protocol (LDAP), which provides the majority of functionality that most directory vendors need.

LDAP is a network protocol that is the primary mechanism for accessing directory services over TCP/IP and has become the de facto standard for directory service access on the Internet. A directory server simply has to support LDAP 2.0 or later, and ADSI can instantly access the directory service without a provider-specific DLL.

ADSI's native support for LDAP means that it can access a very large list of directory services. For older directories such as NT4, vendors have written providers to support ADSI. The list of supported directory services includes the following:

• Active Directory

• Microsoft Exchange Server

• Windows NT 4.0

• NetWare 3.x's bindery-based system

• Novell Directory Service (NDS) and eDirectory

• Netscape iPlanet / Sun ONE

• OpenLDAP

• IBM Lotus Notes

• Microsoft's Internet Information Server (IIS) objects

Before you can start writing scripts that use ADSI, you first need to understand the basic COM concept of interfaces, as well as ADSI's concepts of namespaces, programmatic identifiers (ProgIDs), and ADsPaths.