DCOM and CORBA |
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The COM+ / DNA Tutorial |
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The Advanced Java / JPE Tutorial |
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The CORBA Tutorial |
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n-tier Architecture |
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Security issues |
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Architectural issues |
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Bridging |
There are some features that are fundamental to any technology which supports distributed component development. When it comes to component building and assembling, some of the fundamental features are:
Separation of interface from the implementation Transparency of Location Uniform Exception Handling mechanism Component Object Services Separation of Interface from the Implementation
Both DCOM and CORBA define an Interface Definition Language (IDL) for use by component developers to specify a component's interface independant of a programming language. A component user only needs the IDL of the interface to invoke a function defined in that component. Component developers have the flexibility to develop the component implementation in any programming language of their choice.
Transparency of Location
Both DCOM and CORBA allow components developed using these technologies to communicate in a distributed heterogenous environment. Given a valid object within a client process, it is the object technology's responsibility to locate the server object in the distributed environment and to control subsequent communication between both distributed objects. Location transparency is guaranteed through the use of the proxy-stub mechanism.
Uniform Exception Handling schema
For any object which runs on a heterogenous distributed environment, a uniform, descriptive, elaborate Exception Handling mechanism is necessary. In DCOM, each method call returns a well-defined "flat" structure whose bit settings encode the return status. In CORBA, exception handling is taken care of by Exception Objects. When a distributed object throws an exception object, the ORB transparently transports this object to the client process. By checking the existence and type of the returned object, the client can determine whether or not an exception occured. Microsoft has however announced that a future version of DCOM would support an exception handling mechanism based on exception objects.
Component Object Services
In addition to transparent invocation of requests both DCOM and CORBA come with a complementary set of fundamental component services. Object querying, Object Persistence, Naming, Trading and transaction management for objects are some of the important ones.
The availability of these and other such features simplify component development and help accelerate the development of robust, self-managing components.
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