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- Other types of components also have unique identifiers – however, the concept identifier has a specific role as the code used to represent the meaning in clinical records, documents, messages and data.
Descriptions
A set of textual descriptions are assigned to every concept. These provide the human readable form of a concept. Two types of description are used to represent every concept - Fully Specified Name (FSN) and Synonym. Additionally a Definition maybe added on a case-by case basis if required.
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Example of descriptions for a single concept (US - English)
Relationships
A relationship represents an association between two concepts. Relationships are used to logically define the meaning of a concept in a way that can be processed by a computer. A third concept, called a relationship type (or attribute), is used to represent the meaning of the association between the source and destination concepts. There are different types of relationships available within SNOMED CT.
| Gliffy Diagram |
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| size | 600 |
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| displayName | relationships |
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| name | relationships |
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| pagePin | 1 |
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Example of attribute relationships
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Subtype Relationships
Subtype relationships are the most widely used type of relationship. Subtype relationships use the |is a| relationship type and are therefore also known as |is a| relationships. Almost all active SNOMED CT concepts are the source of at least one |is a| relationship. The only exception is the root concept |SNOMED CT Concept| which is the most general concept. The |is a| relationship states that the source concept is a subtype of the destination concept. SNOMED CT relationships are directional and the |is a| relationship read in the reverse direction states that the destination concept is a supertype of the source concept.
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| size | 600 |
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| displayName | multipleParents |
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| name | multipleParents |
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| pagePin | 1 |
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Each concept can have |is a| relationships to several other concepts (i.e. a concept may have multiple supertype parent concepts). As a result the SNOMED CT hierarchy is not a simple tree but has a structure that is known as a "polyhierarchy".
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| size | 600 |
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| displayName | hierarchyComponents |
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| name | hierarchyComponents |
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| pagePin | 1 |
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Illustration of SNOMED CT subtype hierarchy and terms used to describe it
Attribute Relationships
An attribute relationship contributes to the definition of the source concept by associating it with the value of a defining characteristic. The characteristic (attribute) is specified by the relationship type and the value is provided by the destination of the relationship.
The following example shows the defining relationships of the concept |abscess of heart|. The attribute relationships |associated morphology| and |finding site| are used to associate the source concept |abscess of heart| to respectively the target concepts |abscess|, and |heart structure|.
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| size | 600 |
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| displayName | definition |
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| name | definition |
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| pagePin | 3 |
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The first example below violates the domain constraint of |causative agent|, as descendants of |body structure| are not in the domain of |causative agent|. The second example below is valid with respect to the domain constraint of |causative agent|, because |disorder| is in the domain of |causative agent|. However, this example violates the range constraint of |causative agent|, as descendants of morphological abnormality are not in the range of |causative agent|.
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| size | 600 |
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| displayName | invalidRelationships |
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| name | invalidRelationships |
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| pagePin | 3 |
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A
is
defined if its
| Gloss |
|---|
| t | defining characteristics |
|---|
|
are sufficient to distinguish its meaning from other similar concepts. One example is that the
|acute disease
| is
defined by its two defining
. The
first first is
|is a
| |disease
| and the second
is
|clinical course
| of |sudden onset AND/OR short duration
|. Stating that this concept is
defined means that any concept that
|is a
| |disease
| and has a
|clinical course
| of
|sudden onset AND/OR short duration
| is a subtype of this concept (or the concept itself).
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