In computing, middleware consists of software agents acting as an intermediary between different application components. It is used most often to support complex, distributed applications. The software agents involved may be one or many.
The ObjectWeb consortium gives the following definition of middleware: “In a distributed computing system, middleware is defined as the software layer that lies between the operating system and the applications on each site of the system.”
Middleware is now used to describe web servers, application servers, content management systems, and similar tools that support the application development and delivery process. Middleware is especially integral to modern information based on XML, SOAP, Web services, and service-oriented architecture.
Middleware is the enabling technology of Enterprise application integration.
In addition to the existing vendors updating their wares to address the newly expanded vision, vendors such as Mercator, Vitria, and webMethods were specifically founded to provide Web-oriented middleware tools. Groups such as the Apache Software Foundation and the ObjectWeb consortium encourage the development of open source middleware.
The term middleware is sometimes considered a buzzword.