Version 2.1 of Microsoft Data Access Components (MDAC) introduced two new libraries that complement ADO to provide functionality for Microsoft Access databases previously available only in Data Access Objects (DAO): Microsoft ActiveX Data Objects Extensions for Data Definition Language and Security (ADOX) and Microsoft Jet and Replication Objects (JRO). ADOX allows users to view, create, and modify database structures. JRO includes Jet database replication features, as well as features previously available in the DAO DBEngine object.