ValueSet

A ValueSet resource instance specifies a set of codes drawn from one or more code systems, intended for use in a particular context. Value sets link between CodeSystem definitions and their use in coded elements.

Schema

Elements

Name	Required	Type	Description
url		uri	Canonical identifier for this value set, represented as a URI (globally unique) Details An absolute URI that is used to identify this value set when it is referenced in a specification, model, design or an instance; also called its canonical identifier. This SHOULD be globally unique and SHOULD be a literal address at which at which an authoritative instance of this value set is (or will be) published. This URL can be the target of a canonical reference. It SHALL remain the same when the value set is stored on different servers. Can be a urn:uuid: or a urn:oid: but real http: addresses are preferred. Multiple instances may share the same URL if they have a distinct version. The determination of when to create a new version of a resource (same url, new version) vs. defining a new artifact is up to the author. Considerations for making this decision are found in [Technical and Business Versions](resource.html#versions). In some cases, the resource can no longer be found at the stated url, but the url itself cannot change. Implementations can use the [meta.source](resource.html#meta) element to indicate where the current master source of the resource can be found.
identifier		Identifier[]	Additional identifier for the value set (business identifier) Details A formal identifier that is used to identify this value set when it is represented in other formats, or referenced in a specification, model, design or an instance. Typically, this is used for identifiers that can go in an HL7 V3 II (instance identifier) data type, and can then identify this value set outside of FHIR, where it is not possible to use the logical URI.
version		string	Business version of the value set Details The identifier that is used to identify this version of the value set when it is referenced in a specification, model, design or instance. This is an arbitrary value managed by the value set author and is not expected to be globally unique. For example, it might be a timestamp (e.g. yyyymmdd) if a managed version is not available. There is also no expectation that versions can be placed in a lexicographical sequence. There may be different value set instances that have the same identifier but different versions. The version can be appended to the url in a reference to allow a reference to a particular business version of the value set with the format [url]|[version].
name		string	Name for this value set (computer friendly) Details A natural language name identifying the value set. This name should be usable as an identifier for the module by machine processing applications such as code generation. The name is not expected to be globally unique. The name should be a simple alphanumeric type name to ensure that it is machine-processing friendly.A name should be provided unless the value set is a contained resource (e.g. an anonymous value set in a profile). Most registries will require a name.
title		string	Name for this value set (human friendly) Details A short, descriptive, user-friendly title for the value set. This name does not need to be machine-processing friendly and may contain punctuation, white-space, etc.
status	✓	code	draft | active | retired | unknown Details The status of this value set. Enables tracking the life-cycle of the content. The status of the value set applies to the value set definition (ValueSet.compose) and the associated ValueSet metadata. Expansions do not have a state. Allows filtering of value sets that are appropriate for use versus not.See also the [valueset-workflowStatus](extension-valueset-workflowstatus.html) extension for additional status information related to the editorial process.
experimental		boolean	For testing purposes, not real usage Details A Boolean value to indicate that this value set is authored for testing purposes (or education/evaluation/marketing) and is not intended to be used for genuine usage. Allows filtering of value sets that are appropriate for use versus not.
date		dateTime	Date last changed Details The date (and optionally time) when the value set was created or revised (e.g. the 'content logical definition'). Note that this is not the same as the resource last-modified-date, since the resource may be a secondary representation of the value set. Additional specific dates may be added as extensions or be found by consulting Provenances associated with past versions of the resource.
publisher		string	Name of the publisher (organization or individual) Details The name of the organization or individual that published the value set. Usually an organization but may be an individual. The publisher (or steward) of the value set is the organization or individual primarily responsible for the maintenance and upkeep of the value set. This is not necessarily the same individual or organization that developed and initially authored the content. The publisher is the primary point of contact for questions or issues with the value set. This item SHOULD be populated unless the information is available from context.
contact		ContactDetail[]	Contact details for the publisher Details Contact details to assist a user in finding and communicating with the publisher. May be a web site, an email address, a telephone number, etc.
description		markdown	Natural language description of the value set Details A free text natural language description of the value set from a consumer's perspective. The textual description specifies the span of meanings for concepts to be included within the Value Set Expansion, and also may specify the intended use and limitations of the Value Set. This description can be used to capture details such as why the value set was built, comments about misuse, instructions for clinical use and interpretation, literature references, examples from the paper world, etc. It is not a rendering of the value set as conveyed in the 'text' field of the resource itself. This item SHOULD be populated unless the information is available from context (e.g. the language of the value set is presumed to be the predominant language in the place the value set was created).The description is not intended to describe the semantics of the Value Set - there are no intrinsic semantics separate from the codes contained in its expansion. The description should capture its intended use, which is needed for ensuring integrity for its use in models across future changes. A description should be provided unless the value set is a contained resource (e.g. an anonymous value set in a profile). Most registries will require a description.
useContext		UsageContext[]	The context that the content is intended to support Details The content was developed with a focus and intent of supporting the contexts that are listed. These contexts may be general categories (gender, age, ...) or may be references to specific programs (insurance plans, studies, ...) and may be used to assist with indexing and searching for appropriate value set instances. When multiple useContexts are specified, there is no expectation that all or any of the contexts apply.
jurisdiction		CodeableConcept[]	Intended jurisdiction for value set (if applicable) Details A legal or geographic region in which the value set is intended to be used. It may be possible for the value set to be used in jurisdictions other than those for which it was originally designed or intended.
immutable		boolean	Indicates whether or not any change to the content logical definition may occur Details If this is set to 'true', then no new versions of the content logical definition can be created. Note: Other metadata might still change. Normally immutability is set to 'false', which is the default assumption if it is not populated. Note that the implication is that if this is set to 'true', there may be only one ValueSet version for this definition. Immutability tends to be set to 'true' in one of two cases: - Where the value set, by the nature of its usage, cannot change. For example "All specializations of ACT in ActClassCode" - Where there's no safe way to express the "Purpose" such that someone else could safely make changes to the value set definition. Source workflow control must guarantee that the same URI always yields the same definition.
purpose		markdown	Why this value set is defined Details Explanation of why this value set is needed and why it has been designed as it has. This element does not describe the usage of the value set. Instead, it provides traceability of ''why'' the resource is either needed or ''why'' it is defined as it is. This may be used to point to source materials or specifications that drove the structure of this value set.
copyright		markdown	Use and/or publishing restrictions Details A copyright statement relating to the value set and/or its contents. Copyright statements are generally legal restrictions on the use and publishing of the value set. nullFrequently, the copyright differs between the value set and the codes that are included. The copyright statement should clearly differentiate between these when required.
compose		ValueSetCompose	Content logical definition of the value set (CLD) Details A set of criteria that define the contents of the value set by including or excluding codes selected from the specified code system(s) that the value set draws from. This is also known as the Content Logical Definition (CLD).
id		string	Unique id for inter-element referencing Details Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
extension		Extension[]	Additional content defined by implementations Details May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
modifierExtension		Extension[]	Extensions that cannot be ignored even if unrecognized Details May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions. Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself). There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
lockedDate		date	Fixed date for references with no specified version (transitive) Details The Locked Date is the effective date that is used to determine the version of all referenced Code Systems and Value Set Definitions included in the compose that are not already tied to a specific version. With a defined lockedDate the value set is considered "Locked". Otherwise, the value set may have different expansions as underlying code systems and/or value sets evolve. The interpretation of lockedDate is often dependent on the context - e.g. a SNOMED CT derived value set with a lockedDate will have a different expansion in USA than in UK. If a value set specifies a version for include and exclude statements, and also specifies a locked date, the specified versions need to be available that date, or the value set will not be usable.
inactive		boolean	Whether inactive codes are in the value set Details Whether inactive codes - codes that are not approved for current use - are in the value set. If inactive = true, inactive codes are to be included in the expansion, if inactive = false, the inactive codes will not be included in the expansion. If absent, the behavior is determined by the implementation, or by the applicable $expand parameters (but generally, inactive codes would be expected to be included). Note that in the FHIR terminology framework, "deprecated" does not mean inactive, but in some code systems, e.g. LOINC, "deprecated" does mean inactive. Code systems should define what codes are considered to be inactive. If this is not clearly defined (including in the FHIR code system resource), then all codes are assumed to be active. The Value Set Definition specification defines an ActiveOnly element, which is the reverse of this element e.g. (ValueSet.compose.inactive=FALSE) is the same as (VSD.ActiveOnly=TRUE).
include	✓	ValueSetComposeInclude[]	Include one or more codes from a code system or other value set(s) Details Include one or more codes from a code system or other value set(s). All the conditions in an include must be true. If a system is listed, all the codes from the system are listed. If one or more filters are listed, all of the filters must apply. If one or more value sets are listed, the codes must be in all the value sets. E.g. each include is 'include all the codes that meet all these conditions'.
id		string	Unique id for inter-element referencing Details Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
extension		Extension[]	Additional content defined by implementations Details May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
modifierExtension		Extension[]	Extensions that cannot be ignored even if unrecognized Details May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions. Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself). There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
system		uri	The system the codes come from Details An absolute URI which is the code system from which the selected codes come from. If there are no codes or filters, the entire code system is included. Note that the set of codes that are included may contain abstract codes. See ''Coding.system'' for further documentation about the correct value for the system element.
version		string	Specific version of the code system referred to Details The version of the code system that the codes are selected from, or the special version '*' for all versions. This is used when selecting the descendants of a concept - they may change between versions. If no version is specified, then the exact contents of the value set might not be known until a context of use binds it to a particular version. The special value '*' means all versions; It is at server discretion regarding expansions and which versions must be supported.
concept		ValueSetComposeIncludeConcept[]	A concept defined in the system Details Specifies a concept to be included or excluded. The list of concepts is considered ordered, though the order might not have any particular significance. Typically, the order of an expansion follows that defined in the compose element.
id		string	Unique id for inter-element referencing Details Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
extension		Extension[]	Additional content defined by implementations Details May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
modifierExtension		Extension[]	Extensions that cannot be ignored even if unrecognized Details May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions. Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself). There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
code	✓	code	Code or expression from system Details Specifies a code for the concept to be included or excluded. Expressions are allowed if defined by the underlying code system.
display		string	Text to display for this code for this value set in this valueset Details The text to display to the user for this concept in the context of this valueset. If no display is provided, then applications using the value set use the display specified for the code by the system. The value set resource allows for an alternative display to be specified for when this concept is used in this particular value set. See notes in the value set narrative about the correct use of this element.
designation		ValueSetComposeIncludeConceptDesignation[]	Additional representations for this concept Details Additional representations for this concept when used in this value set - other languages, aliases, specialized purposes, used for particular purposes, etc. Concepts have both a ```display``` and an array of ```designation```. The display is equivalent to a special designation with an implied ```designation.use``` of "primary code" and a language equal to the [Resource Language](resource.html#language).
id		string	Unique id for inter-element referencing Details Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
extension		Extension[]	Additional content defined by implementations Details May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
modifierExtension		Extension[]	Extensions that cannot be ignored even if unrecognized Details May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions. Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself). There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
language		code	Human language of the designation Details The language this designation is defined for. In the absence of a language, the resource language applies.
use		Coding	Types of uses of designations Details A code that represents types of uses of designations. If no use is provided, the designation can be assumed to be suitable for general display to a human user.
value	✓	string	The text value for this designation Details The text value for this designation.
filter		ValueSetComposeIncludeFilter[]	Select codes/concepts by their properties (including relationships) Details Select concepts by specify a matching criterion based on the properties (including relationships) defined by the system, or on filters defined by the system. If multiple filters are specified, they SHALL all be true. Selecting codes by specifying filters based on properties is only possible where the underlying code system defines appropriate properties. Note that in some cases, the underlying code system defines the logical concepts but not the literal codes for the concepts. In such cases, the literal definitions may be provided by a third party.
id		string	Unique id for inter-element referencing Details Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
extension		Extension[]	Additional content defined by implementations Details May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
modifierExtension		Extension[]	Extensions that cannot be ignored even if unrecognized Details May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions. Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself). There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
property	✓	code	A property/filter defined by the code system Details A code that identifies a property or a filter defined in the code system.
op	✓	code	= | is-a | descendent-of | is-not-a | regex | in | not-in | generalizes | exists Details The kind of operation to perform as a part of the filter criteria. In case filter.property represents a property of the system, the operation applies to the selected property. In case filter.property represents a filter of the system, the operation SHALL match one of the CodeSystem.filter.operator values.
value	✓	string	Code from the system, or regex criteria, or boolean value for exists Details The match value may be either a code defined by the system, or a string value, which is a regex match on the literal string of the property value (if the filter represents a property defined in CodeSystem) or of the system filter value (if the filter represents a filter defined in CodeSystem) when the operation is 'regex', or one of the values (true and false), when the operation is 'exists'. Use regex matching with care - full regex matching on every SNOMED CT term is prohibitive, for example.
valueSet		canonical[]	Select the contents included in this value set Details Selects the concepts found in this value set (based on its value set definition). This is an absolute URI that is a reference to ValueSet.url. If multiple value sets are specified this includes the union of the contents of all of the referenced value sets. The value set URI is either a logical reference to a defined value set such as a [SNOMED CT reference set](snomedct.html#implicit), or a direct reference to a value set definition using ValueSet.url. The reference might not refer to an actual FHIR ValueSet resource; in this case, whatever is referred to is an implicit definition of a value set that needs to be clear about how versions are resolved.
exclude		[]	Explicitly exclude codes from a code system or other value sets Details Exclude one or more codes from the value set based on code system filters and/or other value sets. Usually this is used to selectively exclude codes that were included by subsumption in the inclusions. Any display names specified for the codes are ignored.
expansion		ValueSetExpansion	Used when the value set is "expanded" Details A value set can also be "expanded", where the value set is turned into a simple collection of enumerated codes. This element holds the expansion, if it has been performed. Expansion is performed to produce a collection of codes that are ready to use for data entry or validation. Value set expansions are always considered to be stateless - they are a record of the set of codes in the value set at a point in time under a given set of conditions, and are not subject to ongoing maintenance. Expansion.parameter is a simplified list of parameters - a subset of the features of the [Parameters](parameters.html) resource.
id		string	Unique id for inter-element referencing Details Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
extension		Extension[]	Additional content defined by implementations Details May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
modifierExtension		Extension[]	Extensions that cannot be ignored even if unrecognized Details May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions. Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself). There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
identifier		uri	Identifies the value set expansion (business identifier) Details An identifier that uniquely identifies this expansion of the valueset, based on a unique combination of the provided parameters, the system default parameters, and the underlying system code system versions etc. Systems may re-use the same identifier as long as those factors remain the same, and the expansion is the same, but are not required to do so. This is a business identifier. Typically, this uri is a UUID (e.g. urn:uuid:8230ff20-c97a-4167-a59d-dc2cb9df16dd).
timestamp	✓	dateTime	Time ValueSet expansion happened Details The time at which the expansion was produced by the expanding system. This SHOULD be a fully populated instant, but in some circumstances, value sets are expanded by hand, and the expansion is published without that precision.
total		integer	Total number of codes in the expansion Details The total number of concepts in the expansion. If the number of concept nodes in this resource is less than the stated number, then the server can return more using the offset parameter. Paging only applies to flat expansions.
offset		integer	Offset at which this resource starts Details If paging is being used, the offset at which this resource starts. I.e. this resource is a partial view into the expansion. If paging is not being used, this element SHALL NOT be present. Paging only applies to flat expansions. If a filter is applied, the count is the number of concepts that matched the filter, not the number of concepts in an unfiltered view of the expansion.
parameter		ValueSetExpansionParameter[]	Parameter that controlled the expansion process Details A parameter that controlled the expansion process. These parameters may be used by users of expanded value sets to check whether the expansion is suitable for a particular purpose, or to pick the correct expansion. The server decides which parameters to include here, but at a minimum, the list SHOULD include all of the parameters that affect the $expand operation. If the expansion will be persisted all of these parameters SHALL be included. If the codeSystem on the server has a specified version then this version SHALL be provided as a parameter in the expansion (note that not all code systems have a version).
id		string	Unique id for inter-element referencing Details Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
extension		Extension[]	Additional content defined by implementations Details May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
modifierExtension		Extension[]	Extensions that cannot be ignored even if unrecognized Details May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions. Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself). There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
name	✓	string	Name as assigned by the client or server Details Name of the input parameter to the $expand operation; may be a server-assigned name for additional default or other server-supplied parameters used to control the expansion process. The names are assigned at the discretion of the server.
value[x]		string, boolean, integer, decimal, uri, code, dateTime	Value of the named parameter Details The value of the parameter.
contains		ValueSetExpansionContains[]	Codes in the value set Details The codes that are contained in the value set expansion.
id		string	Unique id for inter-element referencing Details Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
extension		Extension[]	Additional content defined by implementations Details May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
modifierExtension		Extension[]	Extensions that cannot be ignored even if unrecognized Details May be used to represent additional information that is not part of the basic definition of the element and that modifies the understanding of the element in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions. Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself). There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
system		uri	System value for the code Details An absolute URI which is the code system in which the code for this item in the expansion is defined.
abstract		boolean	If user cannot select this entry Details If true, this entry is included in the expansion for navigational purposes, and the user cannot select the code directly as a proper value. This should not be understood to exclude its use for searching (e.g. by subsumption testing). The client should know whether it is appropriate for the user to select an abstract code or not.
inactive		boolean	If concept is inactive in the code system Details If the concept is inactive in the code system that defines it. Inactive codes are those that are no longer to be used, but are maintained by the code system for understanding legacy data. It might not be known or specified whether an concept is inactive (and it may depend on the context of use). This should only have a value if the concept is inactive.
version		string	Version in which this code/display is defined Details The version of the code system from this code was taken. Note that a well-maintained code system does not need the version reported, because the meaning of codes is consistent across versions. However this cannot consistently be assured, and when the meaning is not guaranteed to be consistent, the version SHOULD be exchanged. The exact value of the version string is specified by the system from which the code is derived.
code		code	Code - if blank, this is not a selectable code Details The code for this item in the expansion hierarchy. If this code is missing the entry in the hierarchy is a place holder (abstract) and does not represent a valid code in the value set.
display		string	User display for the concept Details The recommended display for this item in the expansion.
designation		[]	Additional representations for this item Details Additional representations for this item - other languages, aliases, specialized purposes, used for particular purposes, etc. These are relevant when the conditions of the expansion do not fix to a single correct representation. The designations provided must be based on the value set and code system definitions.
contains		[]	Codes contained under this entry Details Other codes and entries contained under this entry in the hierarchy. If the expansion uses this element, there is no implication about the logical relationship between them, and the structure cannot be used for logical inferencing. The structure exists to provide navigational assistance for helping human users to locate codes in the expansion.

Search Parameters

Name	Type	Description	Expression
context	token	A use context assigned to the value set	ValueSet.useContext.value as CodeableConcept
context-quantity	quantity	A quantity- or range-valued use context assigned to the value set	ValueSet.useContext.value as Quantity | ValueSet.useContext.value as Range
context-type	token	A type of use context assigned to the value set	ValueSet.useContext.code
date	date	The value set publication date	ValueSet.date
description	string	The description of the value set	ValueSet.description
jurisdiction	token	Intended jurisdiction for the value set	ValueSet.jurisdiction
name	string	Computationally friendly name of the value set	ValueSet.name
publisher	string	Name of the publisher of the value set	ValueSet.publisher
status	token	The current status of the value set	ValueSet.status
title	string	The human-friendly name of the value set	ValueSet.title
url	uri	The uri that identifies the value set	ValueSet.url
version	token	The business version of the value set	ValueSet.version
context-type-quantity	composite	A use context type and quantity- or range-based value assigned to the value set	ValueSet.useContext
context-type-value	composite	A use context type and value assigned to the value set	ValueSet.useContext
identifier	token	External identifier for the value set	ValueSet.identifier
code	token	This special parameter searches for codes in the value set. See additional notes on the ValueSet resource	ValueSet.expansion.contains.code | ValueSet.compose.include.concept.code
expansion	uri	Identifies the value set expansion (business identifier)	ValueSet.expansion.identifier
reference	uri	A code system included or excluded in the value set or an imported value set	ValueSet.compose.include.system

Inherited Elements

Name	Required	Type	Description
id		string	Logical id of this artifact Details The logical id of the resource, as used in the URL for the resource. Once assigned, this value never changes. The only time that a resource does not have an id is when it is being submitted to the server using a create operation.
meta		Meta	Metadata about the resource Details The metadata about the resource. This is content that is maintained by the infrastructure. Changes to the content might not always be associated with version changes to the resource.
implicitRules		uri	A set of rules under which this content was created Details A reference to a set of rules that were followed when the resource was constructed, and which must be understood when processing the content. Often, this is a reference to an implementation guide that defines the special rules along with other profiles etc. Asserting this rule set restricts the content to be only understood by a limited set of trading partners. This inherently limits the usefulness of the data in the long term. However, the existing health eco-system is highly fractured, and not yet ready to define, collect, and exchange data in a generally computable sense. Wherever possible, implementers and/or specification writers should avoid using this element. Often, when used, the URL is a reference to an implementation guide that defines these special rules as part of it's narrative along with other profiles, value sets, etc.
language		code	Language of the resource content Details The base language in which the resource is written. Language is provided to support indexing and accessibility (typically, services such as text to speech use the language tag). The html language tag in the narrative applies to the narrative. The language tag on the resource may be used to specify the language of other presentations generated from the data in the resource. Not all the content has to be in the base language. The Resource.language should not be assumed to apply to the narrative automatically. If a language is specified, it should it also be specified on the div element in the html (see rules in HTML5 for information about the relationship between xml:lang and the html lang attribute).
text		Narrative	Text summary of the resource, for human interpretation Details A human-readable narrative that contains a summary of the resource and can be used to represent the content of the resource to a human. The narrative need not encode all the structured data, but is required to contain sufficient detail to make it "clinically safe" for a human to just read the narrative. Resource definitions may define what content should be represented in the narrative to ensure clinical safety. Contained resources do not have narrative. Resources that are not contained SHOULD have a narrative. In some cases, a resource may only have text with little or no additional discrete data (as long as all minOccurs=1 elements are satisfied). This may be necessary for data from legacy systems where information is captured as a "text blob" or where text is additionally entered raw or narrated and encoded information is added later.
contained		Resource[]	Contained, inline Resources Details These resources do not have an independent existence apart from the resource that contains them - they cannot be identified independently, and nor can they have their own independent transaction scope. This should never be done when the content can be identified properly, as once identification is lost, it is extremely difficult (and context dependent) to restore it again. Contained resources may have profiles and tags In their meta elements, but SHALL NOT have security labels.
extension		Extension[]	Additional content defined by implementations Details May be used to represent additional information that is not part of the basic definition of the resource. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
modifierExtension		Extension[]	Extensions that cannot be ignored Details May be used to represent additional information that is not part of the basic definition of the resource and that modifies the understanding of the element that contains it and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions. Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself). There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

Usage

The FHIR terminology specification is based on two key concepts, originally defined in HL7 v3 Core Principles :

• CodeSystem - declares the existence of and describes a code system or code system supplement and its key properties, and optionally defines a part or all of its content. Also known as Ontology, Terminology, or Enumeration
• ValueSet - specifies a set of codes drawn from one or more code systems, intended for use in a particular context. Value sets link between CodeSystem definitions and their use in coded elements

Value sets have 2 aspects:

• .compose: A definition of which codes are intended to be in the value set ("intension")
• .expansion: The list of codes that are actually in the value set under a given set of conditions ("extension") - see Value Set Expansion

The ValueSet resource can carry either the .compose or the .expansion, both of them, or neither of them (if only the metadata is being represented). There is an "$expand" operation which can be used to ask a server to generate an expansion given the composition rules, in a particular context, and a "$validate-code" operation which can be used to ask a server to check whether a given code or concept is in the value set in a particular context.

Relationships

Value Sets are used by many resources:

• Value sets use CodeSystem resources by referring to them via their canonical reference.
• Value sets are used in StructureDefinition, OperationDefinition, Questionnaire, and other resources to specify the allowable contents for coded elements, or business rules for data processing
• ConceptMap resources describe mappings between value sets
• DataRequirement data types to specify data processing conditions

For a full list of uses, see below.

The Characteristics of the ValueSet resource are derived from Formal Value Set Definitions:

• The ValueSet resource design is based on the functionality described in the OMG CTS 2 specification, along with metadata in the HL7 Value Set Definition specification. Value set resources can be converted to CTS2 value set or code system instances.
• The value set resource is aligned with the Value Set Definition (VSD) project. Not all of the elements defined by the VSD are part of the base resource - some are defined as part of the ValueSet Extensions. In the ValueSet resource, the compose element is the VSD "Content Logical definition".

Background and Context

When using value sets, proper differentiation between a code system and a value set is important. This is one very common area where significant clinical safety risks occur in practice. Implementers should be familiar with the content in Using Codes in Resources.

ValueSet Identification

A value set has 3 identifiers:

• ValueSet.id: the logical id on the system that holds the value set - this changes as it moves from server to server (this id, with the server address prepended, is called the 'literal identity' of the resource)
• ValueSet.url: the canonical URL that never changes for this value set - it is the same in every copy. The element is named url rather than uri for legacy reasons and to strongly encourage providing a resolvable URL as the identifier whenever possible. Ideally, it should be a literal URL that is the location of the master version of the value set, though this is not always possible
• ValueSet.identifier: A system/value pair that is used to identify the value set in other contexts (such as an OID in an HL7 v3 specification)

In addition, any expansion for the value set also has ValueSet.expansion.identifier which uniquely identifies each expansion. For further information regarding resource identification, see Resource Identity.

This means that each value set has 2 different URLs that can be used to reference it - its canonical URL (the url element), and its local location from which it may be retrieved (which includes the id element). Because it is common practice to copy (cache) value sets locally, most references to value sets use the canonical URL.

For example, the value sets published as part of FHIR all have a location ("literal") URI which is the URL where they may be accessed in the FHIR specification itself. Note, though, that while a new version of the FHIR Specification is being prepared, value sets that are published in the drafts will not be found in the current published FHIR specification at their canonical URL.

Alternatively, the identifier and version elements may be used to reference this value set in a design, a profile, a CDA template or HL7 v3 message (in the CD data type valueSet and valueSetVersion properties). These different contexts may make additional restrictions on the possible values of these elements. The identifier is generally not needed when using value sets in a FHIR context, where the canonical URL is always the focus.

Intensional vs Extensional

A value set may be described as intensional or extensional. The terms intensional and extensional come from the fields of mathematical logic and set theory.

An intensional value set is typically algorithmically defined. That is, the code group is defined as a rule e.g. all codes with the word diabetes in their description). The key benefit of intensional code groups is that they can be dynamically updated. Dynamic updating helps healthcare organizations keep current when new drugs (and their associated codes) become available or codes for diseases and other clinical concepts change. An intensional value set designed to contain all of the drugs in the beta blocker category can automatically receive a new beta blocker’s code as soon as it hits the market.

Extensional value sets, meanwhile, are enumerated lists of codes where each code is listed individually. This gives the author and user of the value set more control over the which codes are in the value set, but there is a greater maintenance burden to ensure that the value set is kept up to date.

Referenced By

• DataRequirement
• ElementDefinition
• CodeSystem
• ConceptMap
• ObservationDefinition
• OperationDefinition
• Questionnaire
• ResearchElementDefinition