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

• Since the depth of the hierarchy is not known in any particular case, operations that iterate up or down
the depth of the hierarchy must be done using a recursive algorithm. However, this recursion must usually
be limited since placing the entirety of the SNOMED CT hierarchy in a single tree control is likely to create
performance issues and may exceed physical limits on the capacity of the control.
• Standard tree view controls are not good at displaying the multiple parent nodes that occur in a multi-axial
hierarchy like SNOMED CT. Therefore, some compromises need to be made to present options for
navigation up the hierarchy.
• Effective use of some tree controls requires unique keys for each node. Multiple parents and multiple roots
through the hierarchy mean that the same Concepts will appear in multiple places in the hierarchy.
Therefore, the concept Identifier cannot be used to provide a key that is globally unique within the hierarchy.
4.4.2.3. Using "Part of" Relationships for hierarchy navigation
In addition to the subtype hierarchy represented by | is a | relationships, SNOMED CT also represents a
partonomy hierarchy using | Part of | relationship. This creates an alternative hierarchy which can be also
be used for navigation. The difference between these hierarchies is that:
• The subtype hierarchy relates body structure concepts to supertypes that represent the whole or any part
of an organ or other body part. The fully specified names of these supertype concepts include the word
'structure'.
Example: | Right ventricular structure | (is) | is a | | heart structure |
• The partonomy hierarchy relates body structure to concepts to concept that represent | the entirety of |
or an organ or anatomical structure of which they form part
Example: | Entire right ventricle | (is) | part of | | entire heart |
4.4.2.4. Using other Relationships to navigate SNOMED CT content
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Many SNOMED CT Concepts have relationships with content in other areas of terminology. These
Relationships are one of the ways in which SNOMED CT provides computer readable definitions for medical
concepts. For example, diseases in SNOMED CT generally have a Relationship to the body site affected by
the disorder and a Relationship to the morphology associated with the disease. Procedures in SNOMED CT
might have Relationships to the concept, which defines the type of surgical action being carried and the
procedure site, for example. Examples of Relationships for a disease and a procedure are shown below. A
full list of the Relationships that can be used for each type of Concept can be found in Table 3.
© 2002-2012 International Health Terminology Standards Development Organisation CVR #: 30363434