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The relationships between the records in the core files in the RF2 Release Format are depicted in the following diagram.
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Figure 1. Relationships between files
Each SNOMED CT concept is held as a single row in the Concept file.Each row represents a clinical concept .
Each concept has two or more descriptions associated with it (at least one synonym and at least one Fully Specified Name ). Each description is held as a single row in the Description file, and may only refer to a single concept .
Each relationship , from a source concept to a destination concept , is held as a single row in the Relationship file. The type of each relationship is defined by reference to a linkage concept , also held within the Concept file .
The most basic form of relationship is the subsumption relationship , identifying that one concept is a kind of another concept . For example, an |Outpatient procedure| |Is a| |Procedure|. All the concepts in SNOMED CT form an |Is a| hierarchy , with a parent concept connected to each child concept by an |Is a| relationship . In this hierarchy , a child concept may have more than one parent concept . The root of the hierarchy is the | SNOMED CT Concept |, which has 19 top level children , each forming its own sub-hierarchy . There are no |Is a| relationships that cross from one of these sub-hierarchies to another (e.g. from a concept in the Procedures sub-hierarchy to a concept in the Substances hierarchy .
In addition to the $$ is a $$ relationships, other relationship types
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116680003|is a| |