A classical Object is a blob of intelligence that encapsulates code and data. These objects provide wonderful reuse of code through inheritance, polymorphism and encapsulation. But these classical objects live within a single program and only the language compiler that creates the objects knows their existence. Thus, other programs in the same machine or machine across networks do not have access to these objects. These objects are not reusable and the functionality provided by these objects has to be written again in the specific language and machine that the program that uses it exist. It has to be compiled and used in a specific operating system in a particular platform. Thus, reusability is subject to the same programming language, operating system and platform where the object exist.
A distributed objects is an intelligent piece of code that can live anywhere in the network. It breaks the restrictions of classical objects. Distributed objects are packaged as independent pieces of code that can be accessed by clients in the same machine or machines across the network via method invocations. The language and compiler used to create the objects are totally transparent to the clients. Client need not know where the object resides or in the operating system it executes on. Distributed objects are smart pieces of code that can message each other transparently anywhere in the world. CORBA clients just need the interfaces (method invocation skeleton description) the server object publishes. The interfaces serves as the binding contract between clients and servers.
Components are stand-alone objects that can plug and play across networks, applications, languages, tools and operating systems. Distributed objects are by definition components because of the way they are packaged. Distributed objects infrastructure makes components more autonomous, self-managing and collaborative. The idea behind software component technology is to provide software users and developers the same levels of plug-and -play application interoperability that are available to consumers and manufacturers of electronic parts. The chapter on WWW Objects gives a detailed description of component and component models
Copyright © 1996 Virginia Polytechnic Institute & State University
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Padmapriya Vasudevan
priya@csgrad.cs.vt.edu
Last modified: Mon Oct 14 21:52:09 1996