What is middleware?
Good question. If we listen to the vendors, middleware is anything that helps developers create networked applications. This includes the proverbial kitchen sink. Maybe we can be a bit more specific about what middleware is by describing what it does. First, though, we need a basic model to show where middleware fits among the other pieces of the client/server puzzle.
The term middleware is used to describe a broad array of tools and data that help applications use networked resources and services. Some tools, such as authentication and directories, are in all categorizations. Other services, such as coscheduling of networked resources, secure multicast, and object brokering and messaging, are the major middleware interests of particular communities, such as scientific researchers or business systems vendors. One definition that reflects this breadth of meaning is “Middleware is the intersection of the stuff that network engineers don’t want to do with the stuff that applications developers don’t want to do.
That’s a fair question and one that deserves an answer. Of course, in the IT business, the answer is always, “That depends.” Some people have claimed to me that they think software like HP OpenView is middleware. I’m not going to debate that point, but I will point out that when we refer to middleware on this site, we are generally referring to integration middleware. That still covers a lot of ground, so let’s try a few definitions on for size. These are definitions I have seen in various places. Middleware is software glue. This doesn’t tell us much, but several definitions you’re likely to see on the web will describe it as such. Middleware is the slash in Client/Server. That’s fine as far as it goes, but is deceptively simplistic. This definition concentrates the term on one computing paradigm and masks the complexity of what middleware as a broad category is and does. The Free On-line Dictionary of Computing, by Denis Howe offers this definition. Software that mediates between an
Middleware is one of those tricky words that more or less describes what it does. Middleware is software that connects different parts of an application or a series of applications. Think of it as a sort of glue that holds together a network and its connected computers. Middleware can be a single application, or it can be an entire server. You can also think of middleware as an adapter device that you would run from a new printer to an older computer. The adapter, or middleware, connects the two devices, enabling communication between them and hence functionality. Common middleware packages include the Distributed Computing Environment (DCE) and the Common Object Request Broker Architecture (CORBA). Every type of middleware has the same general purpose: to allow multiple computers to do multiple things across a network, or to allow one computer to do many things or one complicated thing across a network. For example, some middleware is used to link a database system to a Web server, al
