Overview

Relationships are added to link a new concept to one of its supertype parents (in a hierarchical relationship) and to represent defining attribute relationships. Note that at least one hierarchical relationship is required, whereas attribute relationships are optional.

Relationships in an extension follow the same logical design as relationships in the International Edition. They are distributed in a relationship file.

Attributes

In addition to the four common attributes, relationships use six additional attributes.

sourceId

The sourceId identifies the concept being defined by the relationship. Note that this is also the child in a hierarchical relationship.

destinationId

The destinationId identifies a supertype parent of the concept being defined in a hierarchical relationship. In the case of an attribute relationship, the destinationId represents the value of the defining attribute. The destinationId may be a concept in the same extension module or to a concept in a module on which the extension module depends.

relationshipGroup

The relationshipGroup is a number represented by an integer. In the case of an | Is a|  relationship, this number is zero. For attribute relationships, this number is zero unless a relationship is grouped with other relationships in line with the concept model. A detailed discussion on relationship grouping is outside the scope of this document, but for more information on relationship groups please refer to relationship groups in SNOMED CT.

typeId

The typeId is a SCTID that specifies the type of the relationship. In the case of a hierarchical relationship, the value of this attribute is | Is a| . In the case of attribute relationships, the value of this attribute should be a subtype of | Concept model attribute| . Generally speaking, this will be an attribute concept in the International Edition unless additional attributes have been defined within the extension for localized content modelling. Common examples of attribute types include | Finding site|  and | Method| .

characteristicTypeId

The characteristicTypeId is a SCTID which specifies whether this relationship was stated by an author or was inferred by applying a classifier.

modifierId

The modifierId attribute is a SCTID which specifies the existential restriction (some) or the universal restriction (all). Unless you are writing advanced description logic axioms you should use the | Some|  value.

Example

 below, includes two rows from the relationship table of the US edition, 2070901. Note that these relationships form the definition for the extension concept used in the earlier example.

• The namespace identifiers in the id attribute use a namespace allocated to the NLM which indicates these relationship were created by the US NRC
  • The partition identifier in both cases is “12” so we know that these relationships originated in an extension
• The moduleId indicates that these relationships are included in the | US National Library of Medicine maintained module| , which is the same as the module as the concept (defined by these relationships)
• Jumping ahead to the typeId, this identifies that we have an | Is a|  relationship in the 1st row and and an attribute relationship in the 2nd row, where the attribute is | Finding site|
• The sourceId identifies the concept | Persistent asthma|  being described by these relationships
• The destinationId identifies that | Asthma|  is the parent of the | Is a|  relationship and that | Airway structure|  is the value of the | Finding site|  attribute relationship
• Note that the characteristicTypeId and modifierId columns have been omitted from this diagram for brevity