# Appendix E: Concept Enumerations SNOMED CT core *components* have some fields that have values represented by concepts in specific parts of the SNOMED CT hierarchy. These are referred to as *concept* enumerations. The range of permitted values for each of the *concept* enumerations is the set of subtypes of a specified *concept* which is itself a *subtype* of [900000000000442005 |Core metadata concept (core metadata concept)](http://snomed.info/id/900000000000442005). The current set of *concept* enumeration types is shown in Table Appendix E:-1. The values of each of these and the ways they should be used in implemented systems are described in the following subsections. **Core metadata concept (core metadata concept) (900000000000442005)**
ConceptComment
900000000000443000 |Module (core metadata concept)|Each subtype of this concept represents a development module. These concepts provide values to the moduleId field that is present in all component release files. The value indicates the module within which a component was created and is being maintained.
900000000000444006 |Definition status (core metadata concept)|Each subtype of this concept represents a value that can be applied to the concept.definitionStatusId field. This is used to indicate whether the current set of defining relationships applied to a concept are sufficient to define it relative to its supertypes.
900000000000446008 |Description type (core metadata concept)|Each subtype of this concept represents a value that can be applied to the description.typeId field. This is used to indicate whether the description represents a fully specified name, a synonym, a text definition or some other symbolic or textual representation of the associated concept.
900000000000447004 |Case significance (core metadata concept)|Each subtype of this concept represents a value that can be applied to the description.caseSignificanceId field. This is used to indicate whether the text of the term can be modified to by switching characters from upper to lower case (or vice-versa).
900000000000449001 |Characteristic type (core metadata concept)|Each subtype of this concept represents a value that can be applied to the relationship.characteristicTypeId field. This is used to indicate whether a relationship forms part of the definition of the source concept.
900000000000450001 |Modifier (core metadata concept)|Each subtype of this concept represents a value that can be applied to the relationship.modifierId field. This is used to indicate the type of description logic (DL) restriction (some, all, etc.) that applies to the relationship.
900000000000453004 |Identifier scheme (core metadata concept)|Each subtype of this concept represents a value that can be applied to the identifier.identifierSchemeId field. This is used to indicate the scheme to which the identifier value belongs.
*** {% hint style="info" %} Note: Many of the concept enumerations include values that significantly impact the meaning or use of a *component*. Therefore, implementers may find it necessary to partially hard-code the way their systems process particular values. In these cases, the *concept* referenced by the value is only of value when there is a requirement to display a human readable rending of the value. The main exceptions to this are [900000000000443000 |Module (core metadata concept)|](http://snomed.info/id/900000000000443000) and [900000000000453004 |Identifier scheme (core metadata concept)|](http://snomed.info/id/900000000000453004) both of which represent extensible sets of values as new modules or alternative *identifier* schemes may be added in local Extensions . {% endhint %} Provide Feedback