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SNOMED CT is arranged as a polyhierarchy. A hierarchy is defined as an ordered organization of concept codes linked together through IS A relationships. Concept codes are linked to their more general parent concept codes directly above them in a hierarchy. Concepts with more general meanings are usually located at the top of the hierarchy and then at each level down the hierarchy the meanings become increasingly more specialized. 

Selected SNOMED CT attributes have a hierarchical relationship to one another known as attribute hierarchies. In an attribute hierarchy, one general attribute is the parent of one or more specific subtypes of that attribute. Concepts defined using the more general attribute can inherit concepts modeled with the more specialized subtypes of that attribute.


The following are the 19 domains, arranged in alphabetical order. *Those without Concept Models are marked with an asterisk.

HRCM Attribute tables

On the pages that follow, there are tables generated by the Human Readable Concept Model (HRCM). They contain the Attribute Summaries for those domains with attributes, the information on Group(ed), Cardinality, and In-group cardinality for each, and the Range constraints for each.

For information on the definitions of Grouped, Cardinality, and In-group cardinality, please see: IHTSDO Authoring Projects>Projects>MRCM Project>Process for the maintenance of MRCM rules

Modeling: precoordination patterns

SNOMED CT relies on the rules for usefulness to avoid excessive precoordination (see Does It Belong in SNOMED CT?).

Approved precoordination patterns have been created and are available at: Pre-coordination Pattern JIRA Project. For additional information about the fields used in precoordination, see: What the fields in the Pre-coordination Pattern JIRA Project mean.

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