01Overview

In 1965 DENDRAL at Stanford inferred molecular structure from mass spectra; in 1972 MYCIN diagnosed blood infections with about 600 rules, outperforming some physicians. In the 1980s XCON configured DEC computer orders and saved tens of millions of dollars a year. Expert systems were AI’s first commercial wave.

But knowledge acquisition was the bottleneck: experts had to distil rules by hand, maintenance was painful, and edge cases broke the system. In 1987 the market for specialised AI hardware collapsed, the boom faded and the second winter arrived. Its legacy is knowledge representation, inference engines and rule engines, all absorbed into business systems and expert-assist tools.

02History

  1. 1965

    DENDRAL

    An expert system for mass spectrometry.

  2. 1972

    MYCIN

    Rule-driven medical diagnosis.

  3. 1980

    XCON

    The commercial peak of expert systems.

  4. 1987

    The AI winter

    The market for specialised hardware collapses.

03Core concepts

Knowledge base

Domain knowledge stored as rules or facts.

Inference engine

The program that derives conclusions from rules and facts.

Knowledge acquisition

Extracting rules from an expert’s head — the biggest bottleneck.

04Hands-on

Do it once — it beats reading it ten times

Encode 15 rules for a small domain into a forward-chaining engine, then find an input that makes it contradict itself

05Self-check

Say it in your own words first, then open the answer. Whatever you cannot explain is what to review next.

Can you explain "Knowledge base"?

Domain knowledge stored as rules or facts.

Can you explain "Inference engine"?

The program that derives conclusions from rules and facts.

Can you explain "Knowledge acquisition"?

Extracting rules from an expert’s head — the biggest bottleneck.

What problem did it solve, and why was there nothing better at the time?

Go back to the history section: how was this done before, and what did it cost?

If you had to build it today, how would you break it down?

Use the hands-on task above: write a plan of at most three steps before you start.

06Key people

E

Edward Feigenbaum

1936 –

A founder of expert systems and knowledge engineering.

B

Bruce Buchanan

1938 –

Involved in DENDRAL and MYCIN.

07Further reading

  • Expert Systems: Principles and ProgrammingJoseph Giarratano · 1983
  • Building Expert SystemsHayes-Roth, Waterman & Lenat · 1983