Diagnosing with Mycin (1972)

• Purpose: to assist a physician, who was not an expert in the field of antibiotics, with the diagnosis & treatment of blood disorders (and in particular to establish whether the patient was suffering from a serious infection like meningitis).
• Input: symptoms & test results
• Output: a diagnosis, accompanied by a degree of certainty, & recommended therapy
• Knowledge representation: production rules (and simpler data structures)
• Inference engine: Mixed chaining, but principally backward chaining from a top goal: that diagnosis & therapy is needed. Rules are found to satisfy conditions of this rule, then further rules to satisfy these. Evidence may be sought from the user.
• A successful (and enormously influential) expert system:
  • did a complex task.
  performed well: tested against medical students, non-specialist doctors and blood infection specialists, it did better than the former two groups and equalled the latter group.
  • but note that MYCIN was just a laboratory demonstration - it was never marketed, or installed in a hospital and used for routine work.
• These notes are from John's slides. He has a much more thorough example.
• Write down some diagnostic problems that RBSs could be used for.
• Can you think of some diagnostic problems RBSs couldn't be used for?