| There is an increasing need for technology to integrate different incompatible elements into one distributed information environment, enabling sharing resources on the global scale. Development of such system stimulates need for technology behind interoperability. Interoperability means the ability of two or more entities such as objects, programs, applications, or distributed environments to communicate and work together despite differences in the implementation language, the execution environment, or the model abstraction. A number of different distributed computing platforms attempt to address this issues to different extents including OSF's DCE, OMG's CORBA, APM's ANSA. However, these platforms create a new high-level interoperability problem, the heterogeneity of the distributed platforms.; Interoperability between heterogeneous distributed platforms such as DCE and CORBA can normally be achieved by bridge mechanisms. We present a design and implementation of bridge mechanisms that enable transparent cooperation between DCE and CORBA distributed platforms. The design of these mechanisms was driven by the concept of the transparent interoperability between heterogeneous distributed platforms. Conceptually this is done by transforming the necessary information when an object request traverses domain boundaries. This transformation is provided by bridge interfaces that reside at the boundary between the platforms, and transform requests expressed in term of one platform's model into the model of the destination platform. We incorporate pointer swizzling techniques into the proposed mechanisms to allow handling the DCE's pointer types in heterogeneous distributed platforms. The swizzled method requires replicating data in other address spaces to satisfy most remote access locally. The replication can cause the data in the distributed platforms to become inconsistent. To prevent this, the bridge mechanisms must include a coherency protocol to maintain the consistency of the swizzled data in all address spaces that participate in a bridge session. We also discuss alternative methods for handling the DCE's pointer types in distributed platforms environments. The experimental results show that the swizzled method provides performance that is proportional to the number of data segments accessed in remote platforms. |
