Distributed object computing

Remote object method invocation closely resembles remote procedure call (RPC), which is available on a variety of platforms. In  [SMDCE] an extension of the Open Software Foundation's Distributed Computing Environment (see OSF DCE, 1992) is described, offering support for fine-grained distributed objects, system-wide object identity, location-independent method call and dynamic object migration. See slide 6-dce.

Distributed Object Computing

\zline{\fbox{DCE++}}

Distributed Computing Environment

\zline{\fbox{OSF DCE}}
slide: Distributed Object Computing

The unit of distribution supported by DCE++ consists of individual C++ objects, whereas for DCE the unit of distribution amounts to heavy-weight processes. Another improvement over DCE is the symmetry in communication between objects, which means in effect that there is no distinction necessary (as for DCE) between client and server processes. Communication between objects, whether remote or local, is by member call, which in the case of remote objects is automatically mapped onto the underlying DCE RPC mechanism. To establish universally unique identifiers for objects, DCE++ relies on the name management services provided by DCE. This has as an additional advantage that applications may be integrated with any system conforming to the DCE standards. Location-independence is implemented by providing a proxy for each distributed object. Requests to an object that is potentially located elsewhere are automatically addressed to the proxy that, in its turn, identifies the current location of the object and forwards the request. In addition to the distributed name management and communication services, DCE offers supports for light-weight processes, security and the synchronization of distributed clocks. DCE defines a standard for which a number of implementations exist and to which, for example, the Microsoft object linking and embedding facilities adhere. In contrast, DCE++ has only an experimental status. It offers support for employing DCE facilities more conveniently in an object-oriented setting.