For practical reasons, a reference set needs to be identified and named, so it can be referred to unambiguously. In a reference set, the reference set is identified by the refsetId attribute, which refers to a concept. 


This concept is a subtype of the concept .


As for other all concepts in SNOMED CT, descriptions and relationships are added to enable human-readable representation of the concept, and to place the concept in the SNOMED CT hierarchy. The descriptions provide the name of the reference set, and the relationship refers to the concept representing the reference set type. This is illustrated in the diagram below where the concept with the id 49999999102 has the associated description  "Infectious disease simple reference set", and the relationship places the concept as a subtype of the concept .


Reference sets of a particular type are identified by concepts that are subtypes of the concept representing the reference set type. 


900000000000983016|Reference set|
    446609009|Simple type reference set|
    447250001|Complex map type reference set|
    447258008|Ordered type reference set|
    609331003|Extended map type reference set|
    609430003|Concept model reference set|
    705109006|Code to expression type reference set|
    705111002|Map correlation and origin type reference set|
    723564002|MRCM reference set|
    733613001|Intensional definition reference set|
    733614007|Expansion history reference set|
    733618005|Ordered association type reference set|
    733619002|Ordered component type reference set|
    762676003|OWL expression type reference set|
    900000000000456007|Reference set descriptor|
    900000000000480006|Attribute value type|
    900000000000496009|Simple map|
    900000000000506000|Language type|
    900000000000512005|Query specification type|
    900000000000516008|Annotation type|
    900000000000521006|Association type|
    900000000000534007|Module dependency|
    900000000000538005|Description format reference set|

The organization responsible for creating the reference set may add intermediate subtype concepts of the reference set type concept to group together reference sets of that type for which they are responsible. For example, the simple reference sets created by the SNOMED International group responsible for General Practice / Family Practice reference sets are organized as shown below.

2920887014|General Practice / Family Practice reference set|
    450971007|GP/FP reason for encounter reference set|
        450974004|Symptoms and signs reference set for GP/FP reason for encounter|
        450976002|Disorders and diseases reference set for GP/FP reason for encounter|
        450977006|Results reference set for GP/FP reason for encounter|
        450978001|Family history reference set for GP/FP reason for encounter|
        450980007|Allergies reference set for GP/FP reason for encounter|
        450981006|Adverse drug reactions reference set for GP/FP reason for encounter|
        450982004|Processes and procedures reference set for GP/FP reason for encounter|
        450983009|Social history reference set for GP/FP reason for encounter|
    450973005|GP/FP health issue reference set|
        450984003|Symptoms and signs reference set for GP/FP health issue|
        450985002|Disorders and diseases reference set for GP/FP health issue|
        450986001|Results reference set for GP/FP health issue|
        450988000|Family history reference set for GP/FP health issue|
        450989008|Allergies reference set for GP/FP health issue|
        450990004|Adverse drug reactions reference set for GP/FP health issue|
        450991000|Processes and procedures reference set for GP/FP health issue|
        450992007|Social history reference set for GP/FP health issue|