Hardware and Software Concepts:Middleware.

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Middleware

Software plays an important role in distributed systems in which computers are connected across a network. Often, the computers that compose a distributed system are heterogeneous—they use different hardware, run different operating systems and communicate across different network architectures using various network protocols. The nature of distributed systems requires middleware to enable interactions among multiple processes running on one or more computers across a network.

Middleware allows an application running on one computer to communicate with an application running on a remote computer, enabling communications between computers in distributed systems. Middleware also permits applications to run on heterogeneous computer platforms, as long as each computer has the middleware installed. Middleware simplifies application development, because developers do not need to know the details of how the middleware performs its tasks. Developers can concentrate on developing programs rather than developing communication protocols. Open Data Base Connectivity (ODBC) is an example of an API for database access that permits applications to access databases through middleware called an ODBC driver. When developing such applications, developers need to provide only the database to which the application should connect. The ODBC driver handles connect- ing to the database and retrieving the information required by the application. Section 17.3.1, Middleware, through Section 17.3.4, CORBA (Common Object Request Broker Architecture), discuss common middle- ware implementations and protocols that form the back- bone of many distributed systems.

Self Review

1. What are the costs and benefits of using middleware?

2. How does middleware facilitate the construction of hetero- geneous systems?

Ans: 1) Middleware promotes program modularity and facilitates application programming, because the developer does not need to write code to manage interactions between processes. However, communication between middleware and processes incurs overhead compared to direct communication.

2) Middleware facilitates communication between computers using different protocols by translating messages into different formats as they are passed between sender and receiver.

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