The requirements for representing postcoordinated clinical meanings in health records, messages and expression associations are:
Requirement M1: Unambiguous meaning
An expression must be able to specify one unambiguous meaning, independently of the implementation environment.
Requirement M2: Conformance to concept model
Expressions must conform to the rules defined by the SNOMED CT concept model, or be transformable into an expression that conforms to the SNOMED CT concept model. For example, expressions with a clinical finding that is refined using the attribute 272741003 |Laterality| , can be transformed into a conformant expression by applying the laterality to every lateralizable body structure within the definition of the clinical finding. Please note that expressions may either conform to the international SNOMED CT concept model, or a local (e.g. national) extension to the concept model. For more information please refer to For more information please refer to section 12.3.17 and section 12.4.15 of the Terminology Services Guide.
Requirement M3: Subset of SNOMED CT's Description Logic profile
The logical features provided by SNOMED CT compositional grammar must be a subset of those supported by SNOMED CT's Description Logic profile. This profile is primarily based on OWL 2 EL, however some additional features (which are still able to be classified in polynomial time) may also be included. This ensures that all clinical meanings expressed using SNOMED CT compositional grammar can be translated into an equivalent representation in OWL and classified in polynomial time.
Requirement M4: Functional requirements
The logical model must support the following capabilities:
The ability to reference a precoordinated SNOMED CT concept using its identifier and optional human-readable term
Intersection / Conjunction
The ability to connect two focus concepts via a logical AND operator
The ability to refine (or specialise) the meaning of an expression using one or more attributes values
The ability to group a collection of attributes which operate together as part of a refinement
An attribute-value pair which further refines the meaning of the expression
The ability to include an expression as the value of an attribute
The ability to use integers, decimals and strings as attribute values
The ability to specify whether the clinical meaning is 'equivalent to' or a 'subtype of' the expression.