Middleware is an extra layer between the operating system and applications. In computer science, middleware refers to application-neutral programs that mediate between applications in such a way that the complexity of these applications and their infrastructure are hidden. Middleware can also be thought of as a distribution platform, i.e. a protocol (or bundle of protocols) at a higher level than that of ordinary computer communication. In contrast to lower-level network services, which handle simple communication between computers, middleware supports communication between processes. In the field of computer game development, subsystems (or so-called subsystems) for sub-areas such as game physics are referred to as middleware. This middleware is often manufactured and offered by third-party developers.
Middleware is a platform in a complex software system that acts as a “service provider” to enable other otherwise decoupled software components to exchange data. In most cases, this communication takes place with the help of a network, which is made transparent by the middleware for the software components using it. Middleware works at a high level within the layer model: its task is not low-level communication for individual bytes (as is already provided by an operating system, for example). Middleware organizes the transport of complex data (so-called messaging), mediates function calls between the components (so-called remote procedure calls), establishes transaction security via otherwise independent subsystems (function as a transaction monitor), etc.
Middleware software is available as standard software from several vendors. Technically, it provides software interfaces or services. A software component A that wants to use the middleware layer to communicate with a software component B can use these interfaces. The corresponding calls are routed by the middleware software component over a network. As a rule, common network standard protocols are used – almost always IP and TCP, usually HTTP based on them, and SOAP or Web Services, among others. On the recipient side, the middleware converts the request into a function call to software B. If necessary, it forwards the ‘response’ from component B back to component A in the same way.
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The disadvantage of middleware is its size and cumbersomeness. It is rarely possible for the programmer to optimize the performance of these programs. A rough breakdown of middleware for a better understanding:
Application-Oriented Middleware
In addition to communication, the focus is primarily on supporting distributed applications. Examples are both general architectures, such as CORBA, Jakarta EE or the .Net framework, as well as complete operating systems, such as MHP (Multimedia Home Platform), MIDP (Mobile Information Device Profile), a Java-based system for mobile phones
Communication-oriented middleware
The focus here is on abstraction from network programming. Examples are RPC, Web Service.
Message-Oriented Middleware
Message-oriented middleware does not work with method or function calls, but via the exchange of messages. The message format specifies the middleware used. A message-oriented middleware can work both synchronously and asynchronously. In an asynchronous variant, a queue is used in which the message producer places his messages. A consumer can then consume the news. Advantages include the complete decoupling of the message sender and receiver and the fact that applications can continue to work even if subcomponents have failed.
