Active directory service interfaces (ADSI) are one of the more complicated aspects of access control systems, but they are also one of the most important. First, a directory service is an easily customizable cache of information that works as a single point for users to find and use resources and services from any point in your network. Put differently, this is where more stable data, like cardholder information, is stored. ADSI, then, is a set of COM interfaces which are used to access directory services from different networks.
ADSI gathers information distributed throughout your software systems and presents it as one directory, allowing system administrators to manage network resources easily from one central location. They can control any resource regardless of which network actually contains that resource, allowing them to easily complete tasks like adding users and updating security clearances. One more time: ADSI allows you to control all aspects of your various systems from one centralized location.