SNOMED CT Editorial Guide

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In SNOMED CT, and is used in descriptions to represent the operator for logical conjunction. Concepts with the disjunctives (or, and/or) are unacceptable. Instead, there should be separate concepts. There are limited exceptions where and/or is used to represent the operator for inclusive disjunction. This helps to avoid confusion with the literal use of or in common language, i.e. only one of two operands is true; rarely both operands are true. 

Conjunction and Disjunction

andorand/or
SNOMED CT

Conjunction: And

  • A set of operands is true, if and, only if all of its operands are true
  • A and B are true

Exclusive disjunction:  Or

  • Either A or B is true but not both

Inclusive disjunction: And/or

  • A set of operands is true, if and, only if one or more of its operands is true
  • Either A or B is true
    or
  • Both A and B are true

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