Abstract: With the wide application of different distributed object computing systems, interworking between heterogeneous systems becomes necessary. Since interworking between COM and CORBA is most urgent, many CORBA products provide interworking capabilities according to the OMG’s COM/CORBA interworking specification. However, the specification has some limitations on the object identifying and binding mechanism, and these limitations make it difficult to provide portability of applications and interoperability of interworking systems. In this paper, foreign object identifying and binding mechanism is formalized as mapping between foreign object identifiers. Based on this formalization, three methods for object identifying and binding are concluded. And then, an open object identifying and binding mechanism is proposed to achieve portability and interoperability.