Microsoft versus Sun, versus Netscape, versus the Supreme Court! Microsoft's delaying
tactics blocked by the Supreme Court warn of a possible breakup! Given this background
titan giants and the government DCOM site continues to progress with the recent update.
Review of Distributed Component Object Model (DCOM):
Component Object Model (COM) provided objects registered on local systems for dynamic pooling of resources. COM creates multiple object classes that interface by similar methods. Given DCOM COM objects are distributed with remote procedure calls on DCE RPC standards. COM objects provide multiple interfaces representing multiple methods. COM objects connect with pointers to each interface thereby instantiating methods of that COM object.
Common Object Request Broker Architecture (CORBA)
Common Object Request Broker Architecture (CORBA) established by a committee of over 700 companies named the Object Management Group (OMG) provides an open standard for distributed object communication. Whereas DCOM co-registers the object with a Globally Unique Indentifier (GUID) CORBA provides the Object Request Broker (ORB) as a channel to communicate locally and remotely with objects! By reference the method calls are handled in CORBA as if the object is located in the client space, while DCOM GUIDs provide a common channel of communication among interface of COM objects co-located on remote computers!
Client-Server Communications
DCOM and CORBA both provide communications between client and server. Interface Definition Language (IDL) provides encapsulation of the server and interface to the object within the client-server model. IDL provides a contract between the server and clients since the clients invoke methods from the server.
DCOM and CORBA provide interactions between the client and object at the server with RPC-style communications( Remote Procedure Calls). DCOM provides a client stub or proxy that communications with a server stub. In contrast in CORBA the client is the stub and the server stub is the skeleton. Above the Network protocol (TCP/IP) lies the wire protocol, below the client and server stubs.
Table of DCOM Communications
| Client | Server | |||||
| proxy-> | GUID | Registry | Class-> Factory | Object-> | stub->Com lib | |
| com lib-> | SCM reg | ->SCM reg | ||||
| RPC | Channel | ->stub | ||||
| Protocols | Protocols | |||||
Table of Corba Communications
| Client | Server | |||
| Client stub | library <-> | ORB <-> | ORB <-> | obj->obj skeleton |
| Network | <-> | TCP socket | <-> | Network |
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