Skip to end of metadata
Go to start of metadata

A relationship is defined as an association between a source concept and a destination concept. The type of association is indicated by a reference to an attribute concept.


  1. Each relationship provides defining information about the source concept.

  2. Relationships are represented by rows in the Relationship File Specification.


The relationship in the table below states that part of the definition of the concept 74400008 |appendicitis| is that its  363698007 |finding site| is the 66754008 |appendix structure|.

Table: Example of a Relationship (for clarity the US English preferred term is shown for each concept)

Each concept is defined by a set of relationships to other concepts. The resulting definition may be sufficient to distinguish the concept from its parents and siblings in the subtype hierarchy in which case the concept is considered to be sufficiently defined. If the definition is not sufficient to distinguish the concept from its parents and siblings, the concept is said to be primitive. The concept contains a field that is set to indicate whether its definition status is primitive or sufficiently defined. The figure below  illustrates the abstract logical model of a concept, including the defining relationships between concepts(represented by the associations labelled sourceId, destinationId and typeId) and the definition status (represented by the definitionStatusId).


Figure 1.3-1: General abstract logical model of a SNOMED CT concept definition

Stated definition view

A stated concept  definition is the set of relationships (and groups of relationships) that an author (modeler) has stated to be defining characteristics of a concept. The stated view is maintained in the SNOMED CT  editing environment and is reviewed and modified during the process of editing a revised edition of SNOMED CT. The stated view is distributed in a format similar to the relationship file.

Inferred distribution view

An inferred concept definition may include the set of non-redundant defining relationships (and relationship groups ) that are known to be true. This includes those stated and others inferred by inheritance from stated supertype ancestors. However, any relationships (or relationship groups) that are supertypes of other relationships (or relationship groups) are redundant and are not included in this view.

A relationship that is part of a relationshipGroup is only regarded as redundant if the relationshipGroup as a whole subsumes another relationshipGroup. This is the view expressed in the standard SNOMED CT distribution and this same view also forms part of the long normal form.