Various standard terminologies
are already well-developed [30]. Most of these
terminologies are compiled in the National Library of
Medicine’s Unified Medical Language System [36], which
maps concepts from each of over 100 source terminologies
to unique master concepts. Notable standard terminologies
included in the Unified Medical Language System include
the Systematized Nomenclature of Medicine-Clinical Terms
(SNOMED CT) [20], the Logical Observation Identifiers
Names and Codes (LOINC) [37], RxNorm [38], and the
International Classification of Diseases (ICD) [21].