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Object Management Architecture

The Object Management Architecture (OMA) provides standards to build a complete distributed environment. It contains two main parts:

• -System-oriented components - object request brokers (ORBs) and object services
• -Application-oriented components - application objects and common facilities

ORB is the middleware that establishes the client/server relationship between objects. The ORB manages all communications between components and enables them to interact in a heterogeneous and distributed environment. The ORB works independently of the platforms  where the objects reside, which provides greater interoperability. ORBs rely on object services to provide access control, track relocated objects, and create objects.

Common Object Request Broker Architecture (CORBA)

The Object Management Group (OMG) developed the CORBA model for the use of these different services in an environment. This standardization enables many different developers to write hundreds or thousands of components that can interact with other components in an environment without having to know how the component actually works.
When objects communicate with each other, they use pipes, which are inter component communications services. There are different types of pipes, such as remote procedure calls (RPCs) and ORBs. ORBs provide communications between distributed objects. CORBA specifies interface definitions language (IDL) and APIs that interface to the ORB.

COM and DCOM

Component Object Model (COM) defines how components interact and provides an architecture for simple interprocess communication (IPC). COM enables applications to use components on the same systems.
Distributed Component Object Model (DCOM) supports the same model for component interaction, but supports distributed IPC. DCOM enables applications to access objects that reside in different parts of a network. DCOM works as the middleware that enables distributed processing and provides developers with services that support process-to-process communications across networks. DCOM provides ORB services, data connectivity services, distributed messaging services, and distributed transaction services layered over its RPC mechanism.
Without DCOM, programmers would have to write much more complicated code to find necessary objects, set up network sockets, and incorporate the services necessary to allow communication. DCOM takes care of these issues and more, and enables the programmer to focus on his tasks at hand. DCOM has a library that takes care of session handling, synchronization, buffering, fault identification and handling, and data format translation.

Middle wares

Other middleware provide similar functionality to DCOM: ORB, message-oriented middleware (MOM), RPC, ODBC, and so on. DCOM provides ORB services, data connectivity services, distributed messaging services, and distributed transaction services layered over its RPC mechanism.

Object Linking and Embedding

Object linking and embedding (OLE) provides a way for objects to be shared on a local personal computer and to use COM as their foundation. OLE enables objects to be embedded into documents, like graphics, pictures, and spreadsheets.