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Table 3.1.3-1: Example: Defining arthritis as a type of joint disorder
In human readable term...
Relationships and concept definitions
Every active SNOMED CT concept(except the SNOMED CT Concept Root concept) has at least one 116680003 |is a| relationshipto a supertype concept. 116680003 |is a| relationshipsand defining attribute relationshipsare known as the defining characteristicsof SNOMED CT concepts. They are considered defining because they are used to logically represent a conceptby establishing its relationshipswith other concepts. This is accomplished by establishing 116680003 |Is a| relationshipswith one or more defining concepts(called supertypes) and modeling the difference with those supertypes through defining attributes.
Example: 263245004 |Fracture of tarsal bone (disorder)|is defined as:
Example: Group A Streptococcus causes most cases of Streptococcal pharyngitis. However, a small percentage of these cases are caused by other species of Streptococcus. Therefore, it would be incorrect to define 43878008 |Streptococcal sore throat (disorder)|as having 246075003 |causative agent| 80166006 |Streptococcus pyogenes (organism)|. Instead it is correctly defined as having the more general 246075003 |causative agent| 58800005 |Genus Streptococcus (organism)|.
IS A Relationships
116680003 |is a| relationshipsare also known as "Supertype - Subtype relationships" or "Parent - Child relationships". 116680003 |is a| relationshipsare the basis of SNOMED CT's hierarchies, as illustrated below.
Figure 3.1.3-1: Example IS A hierarchy
A conceptcan have more than one 116680003 |is a| relationshipto other concepts. In that case, the conceptwill have parent conceptsin more than one sub-hierarchyof a top-level hierarchy. Subtype relationshipscan be multi-hierarchical.
Figure 3.1.3-2: Example IS A Relationships
An attribute relationshipis an association between two conceptsthat specifies a defining characteristicof one of the concepts(the source of the relationship). Each attribute relationshiphas a name (the type of relationship) and a value (the destination of the relationship).
The combination of the attribute relationshipsand 116680003 |is a| relationshipsassociated with a conceptrepresent the logical definition of that concept. Therefore, the logical conceptdefinition includes one or more supertypes (represented by 116680003 |is a| relationships), and a set of defining attributesthat differentiate it from the other conceptdefinitions.
Since pneumonia is a disorder of the lung, the logical definition of the concept 233604007 |Pneumonia (disorder)|in SNOMED CTincludes the following relationship. The Attribute 363698007 |Finding site|is assigned the value 39607008 |Lung structure (body structure)|.
The full definitions of the concepts 233604007 |Pneumonia (disorder)|,|Infective pneumonia (disorder)| and |Bacterial pneumonia (disorder)| are shown below. Each line represents a defining Attributewith a value.
Figure 3.1.3-3: Definition of |Pneumonia (disorder)|
Figure 3.1.3-4: Definition of |Infective pneumonia (disorder)|
Figure 3.1.3-5: Definition of |Bacterial pneumonia (disorder)|
illustrates some of these Relationshipsgraphically. 116680003 |is a| Relationshipsrelate a conceptto more general conceptsof the same type. In contrast, Attribute Relationships(such as 363698007 |Finding site|and 246075003 |Causative agent|) relate a conceptto relevant values in other branches of the subtype hierarchy.
Figure 3.1.3-6: Illustration of Defining Relationships