Rule-Based Expert Systems[Shortliffe, E. Computer-based medical consultations: MYCIN. New York: Elsevier, 1976.]

MYCIN diagnoses infectious blood diseases using a backward-chained (exhaustive) control strategy.

The algorithm, ignoring certainty factors, is basically backchaining:

Given:

1. list of diseases, Goal-list
2. initial symptoms, DB
3. Rules

For each g ∈ Goal-list do
If prove(g, DB, Rules) then Print (``Diagnosis:'', g)

Function prove (goal, DB, Rules)
If goal ∈ DB then return True
elseif ∃ r ∈ Rules such that r_RHS contains goal
then return provelist(LHS, DB, Rules)[provelist calls prove with each condition of LHS]
else Ask user about goal and return answer