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Role of defining characteristics

Subtyperelationships contribute the hierarchical type based aspect of a Concept definition. This is augmented by defining characteristics that represent the values of a range of relevant attributes. Depending on the nature of the concept these may include including etiology, topography, method, etc.

The attributes that can be applied depend on the domain of the  Concept. For example, a procedure may have a method, and a disorder may have an etiology, but a procedure cannot have an etiology, and disorder cannot have a method. Defining characteristics using a particular attribute will be applied consistently to all Concepts to which it is relevant. Note that this design principle may not be fully realized for all attributes in each release.

Representation of defining characteristics

Defining characteristics are represented as Relationships. The fields are used as follows:

In each release the supported defining characteristics for every Concept are distributed in the relationship file. The supported defining characteristicsare identified by concept that are  descendants of   410662002 |concept model attribute|. Details supported defining attributes for each concept domain are provided in the  SNOMED CT Editorial Guide.

Table 4.3-1: Defining characteristics applied to an example concept

64572001 |disease| is a subtype of |SNOMED CT Concept|. However, many subtypes of |SNOMED CT Concept| are not subtypes of 64572001 |disease| and there are no additional characteristics available to fully define |disease|.

Any |disease| with |Associated morphology|  =  |Inflammation and consolidation|  and
|Finding site|  =  |Lung structure|
is equivalent to or a subtype of |Pneumonia|.

|Catarrhal pneumonia| is a subtype of |Pneumonia|. However, is defining attributes are the same as those that apply to |Pneumonia|. Many other concepts are subtypes of |Pneumonia| and are not subtypes of |Catarrhal pneumonia|. There are no additional defining attributes to distinguish |Catarrhal pneumonia| from |Pneumonia| or its other subtypes.