2.Middleware

Middleware Overview

Definition:

Middleware is the enabling technology of Enterprise application integration. It describes a piece of software that connects two or more software applications so that they can exchange data.

ObjectWeb defines middleware as:

"The software layer that lies between theoperating system and the applications on each side of a distributed computing system in a network.

Origins:

Middleware is a relatively new addition to the computing landscape. It gained popularity in the 1980s as a solution to the problem of how to link new applications to older legacy systems, although the term had been in use since 1968. It also facilitated distributed processing – the connection of multiple applications to create a larger application, usually over a network.

Organizations:

In addition to the existing vendors updating their wares to address the newly expanded vision, vendors such as Mercator, Vitria, Fiorano andwebMethods were specifically founded to provide Web-oriented middleware tools. Groups such as the Apache Software Foundation and the ObjectWeb Consortiumencourage the development of open source middleware.

Types of middleware:

Hurwitz's classification system organizes the many types of middleware that are currently available.These classifications are based on scalability and recoverability:

• Remote Procedure Call (RPCs) — Client makes calls to procedures running on remote systems. Can be asynchronous or synchronous.
• Message Oriented Middleware (MOM) — Messages sent to the client are collected and stored until they are acted upon, while the client continues with other processing.
• Object Request Broker (ORB) — This type of middleware makes it possible for applications to send objects and request services in an object-oriented system.
• SQL-oriented Data Access — middleware between applications and database servers.

Other sources include these additional classifications:

• Transaction processing (TP) monitors — Provides tools and an environment for developing and deploying distributed applications.
• Application servers — software installed on a computer to facilitate the serving (running) of other applications.
• Enterprise Service Bus — An abstraction layer on top of an Enterprise Messaging System.