MOF, the Meta-Object Facility, is an Object Management Group standard for representing metamodels, and manipulating them (through CORBA). The model (but not the representation) of MOF has some similarities to UML, but it was designed primarily for use with CORBA, and hence excludes some facilities which are difficult to use in CORBA and includes other CORBA-specific functions. However, UML can be expressed in terms of MOF, which is done to generate XMI.