For years, middleware has been used to handle data movement across disparate platforms and between incompatible databases. In addition, middleware has made it easy for developers to handle the differences between platforms and databases by writing applications that connect to the middleware layer and by letting the middleware handle the data translation and transport [Talarian Guide, 2000]. In this paper, we will describe a series of related concept about middleware, and especially analyse two types of middleware: Message-Oriented Middleware (MOM) and Object Request Brokers (ORBs), both are competing to become the network standard for linking legacy systems to the web. Finally, by comparing of their advantages and limitations, the specific type of middleware, which is better suited to do the work, is proposed.
Introduction of middleware:
Middleware is the wide range of services layered between the applications and an operating system that provide specialized services and interoperability between distributed applications.
For a variety of reasons including the fact that middleware is a relatively new category of software, the functionality of different kinds of middleware is not standardized [Andy, 1999]. For example, the primary function of transaction processing middleware has to do with control, but many transaction processing products also include communication services. Middleware vendors add functions ensure that their products interoperate with a variety of hardware and software and to help differentiate their product from their competitors'.
Because each product within a middleware category includes a variety of functionality and because the "standard" functions within each category change rapidly, useful distinctions among middleware services are hard to find. At current stage, the middleware market can be broken into five different segments:
1. Transaction processing monitors (TPM)
2. Remote procedure calls (RPC)
3. Object request brokers (ORB)
4. Homegrown middleware solutions
5. Message-oriented middleware (MOM) [Talarian Guide, 2000]