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Role of subtype Relationships

SubtypeRelationships provide the main semantic hierarchy that relates Concepts to one another.

All Active Concepts, except the root Concept, have subtypeRelationships with one or more Concepts. Each of these Relationships indicates that a Concept is a subtype of another Concept.

Representation of Subtype Relationships

SubtypeRelationships are expressed in the same way as all other SNOMED CT Relationships. They are identifiable by their RelationshipType, which refers to a Concept with the Fully Specified Name 116680003 |is a|.

The subtypeRelationshipConcept has a designated Concept Identifier, which is documented in this guide as an Important Concept Identifier.

Subtype Relationships and the Subtype Hierarchy

SubtypeRelationships represent the subtype hierarchy of SNOMED CT. This is illustrated here using a small sample set of concepts and Relationships listed in . [1

Table 4.2-1: Subtype Relationships Example

Only the most proximate 116680003 |is a|relationships are represented in the distribution files. These Relationshipsare shown by the blue lines in . However, a Concept is a subtype of any concept to which it has a direct or indirect 116680003 |is a|Relationship.


53084003 |Bacterial pneumonia| is a subtype of 233604007 |pneumonia| because it is a subtype of 312342009 |infective pneumonia| which is a subtype of |pneumonia.|


Figure 4.2-1: _0e7ff052-9e2f-4878-bbed-2dbd7523cbfb__9Figure 1. Graphical view of the of the Supertypes ofidINLINE53084003|Bacterial pneumonia (disorder)|

The number of links in the chain of 116680003 |is a|Relationships between two Concepts does not alter the logical meaning of the relationship between them. The number of 116680003 |is a|Relationships between two Concepts may change between releases of SNOMED CT as a result of the addition of an intermediate Concept. This does not alter the semantic relationship between them.

Some technical implementation issues are affected by whether a pair of Concepts is linked by a single subtypeRelationship or by a sequence of several subtypeRelationships. In this guide, the following terms are used where this distinction is technically significant:

A given Concept ( Concept -x) may have:

Figure 4.2-2: I nverted hierarchical view of the Supertypes ofidINLINE53084003|Bacterial pneumonia (disorder)|