MYCIN

MYCIN was a rule-based expert system built at Stanford in the early-to-mid 1970s to diagnose bacterial infections and recommend antibiotic therapy, using roughly 600 IF-THEN rules and a "certainty factor" calculus for reasoning under uncertainty. Its domain-independent shell, EMYCIN, was extracted by William van Melle and became a template for later expert systems. It is one of the canonical early expert systems and the paradigm case of backward-chaining inference.

Vault relevance: MYCIN is the load-bearing worked example across two of the vault's threads — the inference-engine lineage (it is the concrete backward-chaining system behind claim-inference-classic-ai-engines) and the rule-based-AI-to-Bayesian-networks arc (its certainty factors are the ad hoc non-Bayesian scheme whose incoherence Heckerman later proved). Its control structure also anchors the finding that ACH's matrix elimination is a mechanism-level false friend for backward chaining, not a twin.

References

• claim-mycin-backward-chaining-is-goal-directed-recursive-subgoal-search — its control structure, from van Melle's own 1984 chapter (Tier 1)
• claim-inference-classic-ai-engines — MYCIN as the paradigm backward-chaining engine; EMYCIN as the reusable shell
• claim-mycin-certainty-factors-non-bayesian-uncertainty — its certainty-factor uncertainty calculus, CF = MB − MD
• claim-heckerman-1986-certainty-factors-require-independence-assumptions — the 1986 critique of MYCIN's CF scheme
• observation-ach-backward-chaining-mechanism-comparison-is-false-friend — MYCIN's backward chaining read against Heuer's ACH
• Creators: entity-edward-shortliffe and entity-bruce-buchanan; EMYCIN and the cited control-structure chapter are William van Melle's work