Hi. Thanks for the answer. I want to write my own schema and incorporate all of the MS attributes in my server. I want to keep the names of object classes and attributes in my server same as they are in AD. For that reason i wanted to modify "top" object class because there are certain attributes which are must in AD's top object class and are not available by default in OpenLDAP's top object class. For example in OpenLDAP attribute "objectClass" is must in top but in AD's "top" objectClass there are more than one "must" and "may" attributes. Is there any way that I can modify "top" object class? And yes, this server will only be compatible with AD. I won't be running any other schema on this server.