What is the relationship between WebService and DCOM/CORBA?

First, COM/DCOM is the component/Distributed Component Model standard, and CORBA is the service standard of distributed applications. For distributed applications Program Create services and service objects to execute services called by the client. Soap is a communication protocol for Distributed Objects Based on XML and HTTP, and a protocol for communication between COM/DCOM and CORBA objects. In fact, the use of soap interoperability and powerful implementation capabilities of CORBA can be well combined.
The applications of CORBA and DCOM cannot implement interoperability, and the two cannot collaborate together. Because in the orpc (DCOM) protocol, objref represents a reference to a running object, and in the CORBA/IIOP, IOR represents an object reference of a server by exchanging interoperable objects. Unfortunately, IOR and objref cannot be associated. The use of soap can achieve horizontal integration of DCOM technology on the vertical application layer, which can better integrate CORBA and DCOM as a whole.
In general, soap is at a lower level than it, a bit similar to IIOP in the role of CORBA and orpc in DCOM. Although DCOM provides some additional protocol functions, it is not available in IIOP or soap. However, many additional DCOM functions are used only for server-to-server communication, while client-to-server communication is redundant.

COM/DCOM belongs to the modeling category, which is similar to the EJB and CORBA component models;
However, CORBA has two meanings: it is both a component model standard and a distributed application service standard. It is a framework (as Liu said ); it can be analogous to Web service infrastructure or COM + (DCOM + MTS extension ).
As a communication protocol, soap is similar to RMI, orpc, and IIOP.
It can be described in a table:

Service Framework basic component model communication protocol interface description Service Discovery Method
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Iiop idl corba Discovery Service
J2EE ejb rmi Java JNDI
COM + COM/DCOM orpc midl Registry
Web service framework Web Service soap WSDL UDDI