Expert System Shells

Building an expert system from scratch means writing an inference engine, a user interface, and an explanation facility every single time — an expert system shell removes this repeated effort by providing all of the general machinery ready-made, leaving only the domain knowledge to be filled in.

What a Shell Provides

Analogy

A shell is to an expert system what a database management system is to a specific database, or what a spreadsheet program is to a specific budget — the general-purpose engine is reused; only the domain content changes.

How a Shell Emerged Historically

The classic medical diagnosis system MYCIN was built with a hand-crafted inference engine specific to medical diagnosis. Researchers later realised the inference engine itself had nothing medical about it — so they stripped out MYCIN's medical rules, keeping only the general reasoning engine, and produced EMYCIN ("Empty MYCIN") — the first well-known expert system shell, which could then be loaded with rules for entirely different domains.

Advantages of Using a Shell

Limitations of Shells

Examples of Expert System Shells