Chapter 15 - People

Etiological Taxonomy, Causal and Disease Process Knowledge 377DISORDER-ETIOLOGYMENINGITIS CYSTITIS BRAIN-ABSCESS-- ---- --/'-- --/'ACLJTF.-MENI~IGITISCHHmllCMENINGITiSBACTERIAL VIRAL PARTIAL-RXGRAM-NEG SKIN-GRGS (OTHER ORGS)TEl FUNGAL/\CRY rTOCOCCUSCOCCIFIGURE 15-7 Portion of etiological taxonomy. (Links representspecialization of cause.)Causal knowledge (Figure 15-8) is represented as rules modified by acertainty factor, as are all MYCIN rules. A causal rule of the form "if Athen B" implies that A is caused by B, the direction of the association thatis most generally useful for interpreting data and refining hypotheses.These rules mention data parameters, taxonomic parameters, or state-categoryparameters. State-category parameters stand for pathophysiological states orcategories of disease (e.g., a mass lesion in the brain). In linking theseconcepts together, it is important to properly distinguish between causaland subtype links. (While we might say that an unknown mass lesion, a