SNOMED CT® Release Format 1 (RF1) Guide - ihtsdo

2.2.2.3.1. Close-to-user expression view ("stated")
The close-to-user (or "stated") view of an expression contains references to the concept (or combination of
concepts) together with refinements as selected by the user or as encoded by a clinical application to represent
the semantics of a single clinical statement (i.e. a discrete clinical record entry).
The close-to-user view of an expression is the faithful representation of the information entered. For clinical
safety and accountability purposes this should be regarded as the primary stored and communicated view
of clinical information encoded using SNOMED CT.
Note: This view includes refinements applied by an application based on selections made in an entry
form as well as those made explicitly. It does not include any relationships that are added based on
classifier rules to make the expression complete or to normalize it.
2.2.2.3.2. Inferred expression views
An inferred expression can be derived from a stated expression by applying rules that take account of the
definition of the refined concept and the associated refined values.
Inferences are drawn based on a consistent set of logical rules applied to the expression taking account of
the definitions of concepts referenced by the expression.
Alternative semantically identical expressions may be generated using different logical transformations. The
purpose of logical transformations is to support accurate and complete information retrieval through
subsumption testing.
In general terms the types of transformation and resulting inferred views for expression are similar to those
for concept definitions. The following sections of the guide identify some of inferred expression views and
some of the differences between expressions and concept definitions.
2.2.2.3.3. Simple, nested and grouped expressions
A typical close-to-user expression consist of a single concept modified by optional refinements as shown in
Figure 18.This may look like a concept definition but it is not defining the concept | hand pain |, it is specifying
a more specific meaning by refining the | finding site | of the concept | hand pain | and adding a severity
qualifier.
Figure 18: Refining a concept to add specificity
Structure and Content Guide | 53
The target of a refinement may itself be refined producing a nested structure. An example of this is the
application of laterality to finding site as shown in Figure 19.
© 2002-2012 International Health Terminology Standards Development Organisation CVR #: 30363434