Provider schema extensions are a way for administrators and ISVs to utilize an extensible DS without having to write additional code. A extensible directory service allows new object classes and properties to be added to the schema, and for new properties to be added to existing object classes. These new elements are added using the schema management objects.
When a new schema class or property is added, it is up to the provider to know where to access and store the instance of a class and the values of its properties. In a typical extensible directory service, this information is stored in the directory service database in the same manner as any other object.
Note that only properties can be added, and not new methods. Adding a new method would require adding new code.