The industry, particularly in the United States, consists of many small companies, or divisions of larger companies, which are selling both expert system development software and support services for assisting with the usage of that software or development of expert systems. Typical annual revenues for a small company or division of a larger company range from $5 million to $20 million annually. The aggregate total of such sales world-wide is in the range of several hundred million dollars per year.
Selling consulting services is a vigorous part of the expert system business. In the United States, consulting is done by major consulting firms, such as Anderson Consulting or SRI International. These major firms compete with many small firms. In Japan, the consulting is done primarily by the computer manufacturers themselves. There is no longer a specialized expert systems hardware business. Expert systems are built for mainframes and for workstations (often UNIX-based).
It's fair to say that the technology of expert systems has had a far greater impact than the expert systems business. Expert system technology is widespread and deeply imbedded.
As expert system techniques matured into a standard information technology in the 1980s, the increasing integration of expert system technology with conventional information technology -- data processing or management information systems -- grew in importance. Conventional technology is mostly the world of IBM mainframes and IBM operating systems. More recently, this world has grown to include distributed networks of engineering workstations. However, it's also the world of a wide variety of personal computers, particularly those running the MS DOS operating system.
Early in its history, commercial expert systems tools were written primarily in LISP and PROLOG, but more recently the trend has been to conventional languages such as C. Commercial companies dedicated to one language or the other (e.g., Symbolics, Lisp Machines Inc., Quintus Prolog) have gone into bankruptcy or have been bought out by other companies.1
Finally, the connection of expert systems to the databases that are managed by conventional information technology methods and groups is essential and is now a standard feature of virtually all expert systems.
1 Interestingly, this trend away from LISP and PROLOG is being reversed in some commercial computing systems. Apple Computer's new personal digital assistant, the Newton, has an operating system (Dylan) written in LISP, and one of the most popular systems for computer-aided design (AUTOCAD) is written in LISP dialect.