Platform SDK: Active Directory, ADSI, and Directory Services
How to Extend the Schema
Once you have decided that schema extension is required, do the following:
Name the new attributes and classes
Obtain OIDs for new attributes and classes
Use display specifiers to integrate new attributes and classes with the user interface, if necessary.
Create a program or script (LDIF or CSV) to install your schema extensions (create new attributes and classes or add attributes to existing classes).