This page is part of the FHIR Specification (v1.0.2: DSTU 2). The current version which supercedes this version is 5.0.0. For a full list of available versions, see the Directory of published versions . Page versions: R5 R4B R4 R3 R2

1.23.0 Element Definition

FHIR Infrastructure

Work Group

Maturity Level: N/A

Ballot Status: DSTU 2

The definition of an element in a resource or extension. The definition includes:

Name, Cardinality, and data type
Definitions, usage notes, requirements
Default or fixed values
Constraints, Length limits, and other usage rules
Terminology Binding
Mappings to other specifications
Structural Usage Information such as Slicing

The ElementDefinition type is the core of the FHIR metadata layer, and is closely (conceptually) aligned to ISO 11179. The DataElement resource is a packaging wrapper around the ElementDefinition type. All the data elements defined in this specification are published as a collection of data elements (XML or JSON).

Structure

Name	Flags	Card.	Type	Description & Constraints
ElementDefinition	Σ I		Element	Definition of an element in a resource or extension Types must be unique by the combination of code and profile Constraints must be unique by key Binding can only be present for coded elements, string, and uri Pattern and value are mutually exclusive default value and meaningWhenMissing are mutually exclusive Min <= Max Pattern may only be specified if there is one type Fixed value may only be specified if there is one type Either a namereference or a fixed value (but not both) is permitted
path	Σ	1..1	string	The path of the element (see the Detailed Descriptions)
representation	Σ	0..*	code	How this element is represented in instances PropertyRepresentation (Required)
name	Σ	0..1	string	Name for this particular element definition (reference target)
label	Σ	0..1	string	Name for element to display with or prompt for element
code	Σ	0..*	Coding	Defining code LOINC Codes (Example)
slicing	Σ I	0..1	Element	This element is sliced - slices follow If there are no discriminators, there must be a definition
discriminator	Σ	0..*	string	Element values that used to distinguish the slices
description	Σ I	0..1	string	Text description of how slicing works (or not)
ordered	Σ	0..1	boolean	If elements must be in same order as slices
rules	Σ	1..1	code	closed \| open \| openAtEnd SlicingRules (Required)
short	Σ	0..1	string	Concise definition for xml presentation
definition	Σ	0..1	markdown	Full formal definition as narrative text
comments	Σ	0..1	markdown	Comments about the use of this element
requirements	Σ	0..1	markdown	Why is this needed?
alias	Σ	0..*	string	Other names
min	Σ I	0..1	integer	Minimum Cardinality
max	Σ I	0..1	string	Maximum Cardinality (a number or ) Max SHALL be a number or ""
base	Σ	0..1	Element	Base definition information for tools
path	Σ	1..1	string	Path that identifies the base element
min	Σ	1..1	integer	Min cardinality of the base element
max	Σ	1..1	string	Max cardinality of the base element
type	Σ I	0..*	Element	Data type and Profile for this element Aggregation may only be specified if one of the allowed types for the element is a resource
code	Σ	1..1	code	Name of Data type or Resource FHIRDefinedType (Required)
profile	Σ	0..*	uri	Profile (StructureDefinition) to apply (or IG)
aggregation	Σ I	0..*	code	contained \| referenced \| bundled - how aggregated AggregationMode (Required)
nameReference	Σ I	0..1	string	To another element constraint (by element.name)
defaultValue[x]	Σ I	0..1	*	Specified value it missing from instance
meaningWhenMissing	Σ I	0..1	markdown	Implicit meaning when this element is missing
fixed[x]	Σ I	0..1	*	Value must be exactly this
pattern[x]	Σ I	0..1	*	Value must have at least these property values
example[x]	Σ	0..1	*	Example value: [as defined for type]
minValue[x]	Σ	0..1	*	Minimum Allowed Value (for some types)
maxValue[x]	Σ	0..1	*	Maximum Allowed Value (for some types)
maxLength	Σ	0..1	integer	Max length for strings
condition	Σ	0..*	id	Reference to invariant about presence
constraint	Σ	0..*	Element	Condition that must evaluate to true
key	Σ I	1..1	id	Target of 'condition' reference above
requirements	Σ	0..1	string	Why this constraint necessary or appropriate
severity	Σ	1..1	code	error \| warning ConstraintSeverity (Required)
human	Σ	1..1	string	Human description of constraint
xpath	Σ	1..1	string	XPath expression of constraint
mustSupport	Σ	0..1	boolean	If the element must supported
isModifier	Σ	0..1	boolean	If this modifies the meaning of other elements
isSummary	Σ	0..1	boolean	Include when _summary = true?
binding	Σ I	0..1	Element	ValueSet details if this is coded provide either a reference or a description (or both)
strength	Σ	1..1	code	required \| extensible \| preferred \| example BindingStrength (Required)
description	Σ I	0..1	string	Human explanation of the value set
valueSet[x]	Σ I	0..1		Source of value set URI SHALL start with http:// or https://
valueSetUri			uri
valueSetReference			Reference(ValueSet)
mapping	Σ	0..*	Element	Map element to another set of definitions
identity	Σ	1..1	id	Reference to mapping declaration
language	Σ	0..1	code	Computable language of mapping MimeType (Required)
map	Σ	1..1	string	Details of the mapping
Documentation for this format

UML Diagram

XML Template

<[name] xmlns="http://hl7.org/fhir"> 
 <!-- from Element: extension -->
 <path value="[string]"/><!-- 1..1 The path of the element (see the Detailed Descriptions) -->
 <representation value="[code]"/><!-- 0..* How this element is represented in instances -->
 <name value="[string]"/><!-- 0..1 Name for this particular element definition (reference target) -->
 <label value="[string]"/><!-- 0..1 Name for element to display with or prompt for element -->
 <code><!-- 0..* Coding Defining code --></code>
 <slicing>  <!-- 0..1 This element is sliced - slices follow -->
  <discriminator value="[string]"/><!-- 0..* Element values that used to distinguish the slices -->
  <description value="[string]"/><!--  0..1 Text description of how slicing works (or not) -->
  <ordered value="[boolean]"/><!-- 0..1 If elements must be in same order as slices -->
  <rules value="[code]"/><!-- 1..1 closed | open | openAtEnd -->
 </slicing>
 <short value="[string]"/><!-- 0..1 Concise definition for xml presentation -->
 <definition value="[markdown]"/><!-- 0..1 Full formal definition as narrative text -->
 <comments value="[markdown]"/><!-- 0..1 Comments about the use of this element -->
 <requirements value="[markdown]"/><!-- 0..1 Why is this needed? -->
 <alias value="[string]"/><!-- 0..* Other names -->
 <min value="[integer]"/><!--  0..1 Minimum Cardinality -->
 <max value="[string]"/><!--  0..1 Maximum Cardinality (a number or *) -->
 <base>  <!-- 0..1 Base definition information for tools -->
  <path value="[string]"/><!-- 1..1 Path that identifies the base element -->
  <min value="[integer]"/><!-- 1..1 Min cardinality of the base element -->
  <max value="[string]"/><!-- 1..1 Max cardinality of the base element -->
 </base>
 <type>  <!--  0..* Data type and Profile for this element -->
  <code value="[code]"/><!-- 1..1 Name of Data type or Resource -->
  <profile value="[uri]"/><!-- 0..* Profile (StructureDefinition) to apply (or IG) -->
  <aggregation value="[code]"/><!--  0..* contained | referenced | bundled - how aggregated -->
 </type>
 <nameReference value="[string]"/><!--  0..1 To another element constraint (by element.name) -->
 <defaultValue[x]><!--  0..1 * Specified value it missing from instance --></defaultValue[x]>
 <meaningWhenMissing value="[markdown]"/><!--  0..1 Implicit meaning when this element is missing -->
 <fixed[x]><!--  0..1 * Value must be exactly this --></fixed[x]>
 <pattern[x]><!--  0..1 * Value must have at least these property values --></pattern[x]>
 <example[x]><!-- 0..1 * Example value: [as defined for type] --></example[x]>
 <minValue[x]><!-- 0..1 * Minimum Allowed Value (for some types) --></minValue[x]>
 <maxValue[x]><!-- 0..1 * Maximum Allowed Value (for some types) --></maxValue[x]>
 <maxLength value="[integer]"/><!-- 0..1 Max length for strings -->
 <condition value="[id]"/><!-- 0..* Reference to invariant about presence -->
 <constraint>  <!-- 0..* Condition that must evaluate to true -->
  <key value="[id]"/><!--  1..1 Target of 'condition' reference above -->
  <requirements value="[string]"/><!-- 0..1 Why this constraint necessary or appropriate -->
  <severity value="[code]"/><!-- 1..1 error | warning -->
  <human value="[string]"/><!-- 1..1 Human description of constraint -->
  <xpath value="[string]"/><!-- 1..1 XPath expression of constraint -->
 </constraint>
 <mustSupport value="[boolean]"/><!-- 0..1 If the element must supported -->
 <isModifier value="[boolean]"/><!-- 0..1 If this modifies the meaning of other elements -->
 <isSummary value="[boolean]"/><!-- 0..1 Include when _summary = true? -->
 <binding>  <!--  0..1 ValueSet details if this is coded -->
  <strength value="[code]"/><!-- 1..1 required | extensible | preferred | example -->
  <description value="[string]"/><!--  0..1 Human explanation of the value set -->
  <valueSet[x]><!--  0..1 uri|Reference(ValueSet) Source of value set --></valueSet[x]>
 </binding>
 <mapping>  <!-- 0..* Map element to another set of definitions -->
  <identity value="[id]"/><!-- 1..1 Reference to mapping declaration -->
  <language value="[code]"/><!-- 0..1 Computable language of mapping  -->
  <map value="[string]"/><!-- 1..1 Details of the mapping -->
 </mapping>
</[name]>

JSON Template

{
  // from Element: extension
  "path" : "<string>", // R!  The path of the element (see the Detailed Descriptions)
  "representation" : ["<code>"], // How this element is represented in instances
  "name" : "<string>", // Name for this particular element definition (reference target)
  "label" : "<string>", // Name for element to display with or prompt for element
  "code" : [{ Coding }], // Defining code
  "slicing" : { // This element is sliced - slices follow
    "discriminator" : ["<string>"], // Element values that used to distinguish the slices
    "description" : "<string>", // C? Text description of how slicing works (or not)
    "ordered" : <boolean>, // If elements must be in same order as slices
    "rules" : "<code>" // R!  closed | open | openAtEnd
  },
  "short" : "<string>", // Concise definition for xml presentation
  "definition" : "<markdown>", // Full formal definition as narrative text
  "comments" : "<markdown>", // Comments about the use of this element
  "requirements" : "<markdown>", // Why is this needed?
  "alias" : ["<string>"], // Other names
  "min" : <integer>, // C? Minimum Cardinality
  "max" : "<string>", // C? Maximum Cardinality (a number or *)
  "base" : { // Base definition information for tools
    "path" : "<string>", // R!  Path that identifies the base element
    "min" : <integer>, // R!  Min cardinality of the base element
    "max" : "<string>" // R!  Max cardinality of the base element
  },
  "type" : [{ // C? Data type and Profile for this element
    "code" : "<code>", // R!  Name of Data type or Resource
    "profile" : ["<uri>"], // Profile (StructureDefinition) to apply (or IG)
    "aggregation" : ["<code>"] // C? contained | referenced | bundled - how aggregated
  }],
  "nameReference" : "<string>", // C? To another element constraint (by element.name)
  // defaultValue[x]: Specified value it missing from instance. One of these 23:
  "defaultValueInteger" : <integer>,
  "defaultValueDecimal" : <decimal>,
  "defaultValueDateTime" : "<dateTime>",
  "defaultValueDate" : "<date>",
  "defaultValueInstant" : "<instant>",
  "defaultValueString" : "<string>",
  "defaultValueUri" : "<uri>",
  "defaultValueBoolean" : <boolean>,
  "defaultValueCode" : "<code>",
  "defaultValueBase64Binary" : "<base64Binary>",
  "defaultValueCoding" : { Coding },
  "defaultValueCodeableConcept" : { CodeableConcept },
  "defaultValueAttachment" : { Attachment },
  "defaultValueIdentifier" : { Identifier },
  "defaultValueQuantity" : { Quantity },
  "defaultValueRange" : { Range },
  "defaultValuePeriod" : { Period },
  "defaultValueRatio" : { Ratio },
  "defaultValueHumanName" : { HumanName },
  "defaultValueAddress" : { Address },
  "defaultValueContactPoint" : { ContactPoint },
  "defaultValueSchedule" : { Schedule },
  "defaultValueReference" : { Reference },
  "meaningWhenMissing" : "<markdown>", // C? Implicit meaning when this element is missing
  // fixed[x]: Value must be exactly this. One of these 23:
  "fixedInteger" : <integer>,
  "fixedDecimal" : <decimal>,
  "fixedDateTime" : "<dateTime>",
  "fixedDate" : "<date>",
  "fixedInstant" : "<instant>",
  "fixedString" : "<string>",
  "fixedUri" : "<uri>",
  "fixedBoolean" : <boolean>,
  "fixedCode" : "<code>",
  "fixedBase64Binary" : "<base64Binary>",
  "fixedCoding" : { Coding },
  "fixedCodeableConcept" : { CodeableConcept },
  "fixedAttachment" : { Attachment },
  "fixedIdentifier" : { Identifier },
  "fixedQuantity" : { Quantity },
  "fixedRange" : { Range },
  "fixedPeriod" : { Period },
  "fixedRatio" : { Ratio },
  "fixedHumanName" : { HumanName },
  "fixedAddress" : { Address },
  "fixedContactPoint" : { ContactPoint },
  "fixedSchedule" : { Schedule },
  "fixedReference" : { Reference },
  // pattern[x]: Value must have at least these property values. One of these 23:
  "patternInteger" : <integer>,
  "patternDecimal" : <decimal>,
  "patternDateTime" : "<dateTime>",
  "patternDate" : "<date>",
  "patternInstant" : "<instant>",
  "patternString" : "<string>",
  "patternUri" : "<uri>",
  "patternBoolean" : <boolean>,
  "patternCode" : "<code>",
  "patternBase64Binary" : "<base64Binary>",
  "patternCoding" : { Coding },
  "patternCodeableConcept" : { CodeableConcept },
  "patternAttachment" : { Attachment },
  "patternIdentifier" : { Identifier },
  "patternQuantity" : { Quantity },
  "patternRange" : { Range },
  "patternPeriod" : { Period },
  "patternRatio" : { Ratio },
  "patternHumanName" : { HumanName },
  "patternAddress" : { Address },
  "patternContactPoint" : { ContactPoint },
  "patternSchedule" : { Schedule },
  "patternReference" : { Reference },
  // example[x]: Example value: [as defined for type]. One of these 23:
  "exampleInteger" : <integer>,
  "exampleDecimal" : <decimal>,
  "exampleDateTime" : "<dateTime>",
  "exampleDate" : "<date>",
  "exampleInstant" : "<instant>",
  "exampleString" : "<string>",
  "exampleUri" : "<uri>",
  "exampleBoolean" : <boolean>,
  "exampleCode" : "<code>",
  "exampleBase64Binary" : "<base64Binary>",
  "exampleCoding" : { Coding },
  "exampleCodeableConcept" : { CodeableConcept },
  "exampleAttachment" : { Attachment },
  "exampleIdentifier" : { Identifier },
  "exampleQuantity" : { Quantity },
  "exampleRange" : { Range },
  "examplePeriod" : { Period },
  "exampleRatio" : { Ratio },
  "exampleHumanName" : { HumanName },
  "exampleAddress" : { Address },
  "exampleContactPoint" : { ContactPoint },
  "exampleSchedule" : { Schedule },
  "exampleReference" : { Reference },
  // minValue[x]: Minimum Allowed Value (for some types). One of these 23:
  "minValueInteger" : <integer>,
  "minValueDecimal" : <decimal>,
  "minValueDateTime" : "<dateTime>",
  "minValueDate" : "<date>",
  "minValueInstant" : "<instant>",
  "minValueString" : "<string>",
  "minValueUri" : "<uri>",
  "minValueBoolean" : <boolean>,
  "minValueCode" : "<code>",
  "minValueBase64Binary" : "<base64Binary>",
  "minValueCoding" : { Coding },
  "minValueCodeableConcept" : { CodeableConcept },
  "minValueAttachment" : { Attachment },
  "minValueIdentifier" : { Identifier },
  "minValueQuantity" : { Quantity },
  "minValueRange" : { Range },
  "minValuePeriod" : { Period },
  "minValueRatio" : { Ratio },
  "minValueHumanName" : { HumanName },
  "minValueAddress" : { Address },
  "minValueContactPoint" : { ContactPoint },
  "minValueSchedule" : { Schedule },
  "minValueReference" : { Reference },
  // maxValue[x]: Maximum Allowed Value (for some types). One of these 23:
  "maxValueInteger" : <integer>,
  "maxValueDecimal" : <decimal>,
  "maxValueDateTime" : "<dateTime>",
  "maxValueDate" : "<date>",
  "maxValueInstant" : "<instant>",
  "maxValueString" : "<string>",
  "maxValueUri" : "<uri>",
  "maxValueBoolean" : <boolean>,
  "maxValueCode" : "<code>",
  "maxValueBase64Binary" : "<base64Binary>",
  "maxValueCoding" : { Coding },
  "maxValueCodeableConcept" : { CodeableConcept },
  "maxValueAttachment" : { Attachment },
  "maxValueIdentifier" : { Identifier },
  "maxValueQuantity" : { Quantity },
  "maxValueRange" : { Range },
  "maxValuePeriod" : { Period },
  "maxValueRatio" : { Ratio },
  "maxValueHumanName" : { HumanName },
  "maxValueAddress" : { Address },
  "maxValueContactPoint" : { ContactPoint },
  "maxValueSchedule" : { Schedule },
  "maxValueReference" : { Reference },
  "maxLength" : <integer>, // Max length for strings
  "condition" : ["<id>"], // Reference to invariant about presence
  "constraint" : [{ // Condition that must evaluate to true
    "key" : "<id>", // C? R!  Target of 'condition' reference above
    "requirements" : "<string>", // Why this constraint necessary or appropriate
    "severity" : "<code>", // R!  error | warning
    "human" : "<string>", // R!  Human description of constraint
    "xpath" : "<string>" // R!  XPath expression of constraint
  }],
  "mustSupport" : <boolean>, // If the element must supported
  "isModifier" : <boolean>, // If this modifies the meaning of other elements
  "isSummary" : <boolean>, // Include when _summary = true?
  "binding" : { // C? ValueSet details if this is coded
    "strength" : "<code>", // R!  required | extensible | preferred | example
    "description" : "<string>", // C? Human explanation of the value set
    // valueSet[x]: Source of value set. One of these 2:
    "valueSetUri" : "<uri>"
    "valueSetReference" : { Reference(ValueSet) }
  },
  "mapping" : [{ // Map element to another set of definitions
    "identity" : "<id>", // R!  Reference to mapping declaration
    "language" : "<code>", // Computable language of mapping 
    "map" : "<string>" // R!  Details of the mapping
  }]
}

Structure

Name	Flags	Card.	Type	Description & Constraints
ElementDefinition	Σ I		Element	Definition of an element in a resource or extension Types must be unique by the combination of code and profile Constraints must be unique by key Binding can only be present for coded elements, string, and uri Pattern and value are mutually exclusive default value and meaningWhenMissing are mutually exclusive Min <= Max Pattern may only be specified if there is one type Fixed value may only be specified if there is one type Either a namereference or a fixed value (but not both) is permitted
path	Σ	1..1	string	The path of the element (see the Detailed Descriptions)
representation	Σ	0..*	code	How this element is represented in instances PropertyRepresentation (Required)
name	Σ	0..1	string	Name for this particular element definition (reference target)
label	Σ	0..1	string	Name for element to display with or prompt for element
code	Σ	0..*	Coding	Defining code LOINC Codes (Example)
slicing	Σ I	0..1	Element	This element is sliced - slices follow If there are no discriminators, there must be a definition
discriminator	Σ	0..*	string	Element values that used to distinguish the slices
description	Σ I	0..1	string	Text description of how slicing works (or not)
ordered	Σ	0..1	boolean	If elements must be in same order as slices
rules	Σ	1..1	code	closed \| open \| openAtEnd SlicingRules (Required)
short	Σ	0..1	string	Concise definition for xml presentation
definition	Σ	0..1	markdown	Full formal definition as narrative text
comments	Σ	0..1	markdown	Comments about the use of this element
requirements	Σ	0..1	markdown	Why is this needed?
alias	Σ	0..*	string	Other names
min	Σ I	0..1	integer	Minimum Cardinality
max	Σ I	0..1	string	Maximum Cardinality (a number or ) Max SHALL be a number or ""
base	Σ	0..1	Element	Base definition information for tools
path	Σ	1..1	string	Path that identifies the base element
min	Σ	1..1	integer	Min cardinality of the base element
max	Σ	1..1	string	Max cardinality of the base element
type	Σ I	0..*	Element	Data type and Profile for this element Aggregation may only be specified if one of the allowed types for the element is a resource
code	Σ	1..1	code	Name of Data type or Resource FHIRDefinedType (Required)
profile	Σ	0..*	uri	Profile (StructureDefinition) to apply (or IG)
aggregation	Σ I	0..*	code	contained \| referenced \| bundled - how aggregated AggregationMode (Required)
nameReference	Σ I	0..1	string	To another element constraint (by element.name)
defaultValue[x]	Σ I	0..1	*	Specified value it missing from instance
meaningWhenMissing	Σ I	0..1	markdown	Implicit meaning when this element is missing
fixed[x]	Σ I	0..1	*	Value must be exactly this
pattern[x]	Σ I	0..1	*	Value must have at least these property values
example[x]	Σ	0..1	*	Example value: [as defined for type]
minValue[x]	Σ	0..1	*	Minimum Allowed Value (for some types)
maxValue[x]	Σ	0..1	*	Maximum Allowed Value (for some types)
maxLength	Σ	0..1	integer	Max length for strings
condition	Σ	0..*	id	Reference to invariant about presence
constraint	Σ	0..*	Element	Condition that must evaluate to true
key	Σ I	1..1	id	Target of 'condition' reference above
requirements	Σ	0..1	string	Why this constraint necessary or appropriate
severity	Σ	1..1	code	error \| warning ConstraintSeverity (Required)
human	Σ	1..1	string	Human description of constraint
xpath	Σ	1..1	string	XPath expression of constraint
mustSupport	Σ	0..1	boolean	If the element must supported
isModifier	Σ	0..1	boolean	If this modifies the meaning of other elements
isSummary	Σ	0..1	boolean	Include when _summary = true?
binding	Σ I	0..1	Element	ValueSet details if this is coded provide either a reference or a description (or both)
strength	Σ	1..1	code	required \| extensible \| preferred \| example BindingStrength (Required)
description	Σ I	0..1	string	Human explanation of the value set
valueSet[x]	Σ I	0..1		Source of value set URI SHALL start with http:// or https://
valueSetUri			uri
valueSetReference			Reference(ValueSet)
mapping	Σ	0..*	Element	Map element to another set of definitions
identity	Σ	1..1	id	Reference to mapping declaration
language	Σ	0..1	code	Computable language of mapping MimeType (Required)
map	Σ	1..1	string	Details of the mapping
Documentation for this format

UML Diagram

XML Template

<[name] xmlns="http://hl7.org/fhir"> 
 <!-- from Element: extension -->
 <path value="[string]"/><!-- 1..1 The path of the element (see the Detailed Descriptions) -->
 <representation value="[code]"/><!-- 0..* How this element is represented in instances -->
 <name value="[string]"/><!-- 0..1 Name for this particular element definition (reference target) -->
 <label value="[string]"/><!-- 0..1 Name for element to display with or prompt for element -->
 <code><!-- 0..* Coding Defining code --></code>
 <slicing>  <!-- 0..1 This element is sliced - slices follow -->
  <discriminator value="[string]"/><!-- 0..* Element values that used to distinguish the slices -->
  <description value="[string]"/><!--  0..1 Text description of how slicing works (or not) -->
  <ordered value="[boolean]"/><!-- 0..1 If elements must be in same order as slices -->
  <rules value="[code]"/><!-- 1..1 closed | open | openAtEnd -->
 </slicing>
 <short value="[string]"/><!-- 0..1 Concise definition for xml presentation -->
 <definition value="[markdown]"/><!-- 0..1 Full formal definition as narrative text -->
 <comments value="[markdown]"/><!-- 0..1 Comments about the use of this element -->
 <requirements value="[markdown]"/><!-- 0..1 Why is this needed? -->
 <alias value="[string]"/><!-- 0..* Other names -->
 <min value="[integer]"/><!--  0..1 Minimum Cardinality -->
 <max value="[string]"/><!--  0..1 Maximum Cardinality (a number or *) -->
 <base>  <!-- 0..1 Base definition information for tools -->
  <path value="[string]"/><!-- 1..1 Path that identifies the base element -->
  <min value="[integer]"/><!-- 1..1 Min cardinality of the base element -->
  <max value="[string]"/><!-- 1..1 Max cardinality of the base element -->
 </base>
 <type>  <!--  0..* Data type and Profile for this element -->
  <code value="[code]"/><!-- 1..1 Name of Data type or Resource -->
  <profile value="[uri]"/><!-- 0..* Profile (StructureDefinition) to apply (or IG) -->
  <aggregation value="[code]"/><!--  0..* contained | referenced | bundled - how aggregated -->
 </type>
 <nameReference value="[string]"/><!--  0..1 To another element constraint (by element.name) -->
 <defaultValue[x]><!--  0..1 * Specified value it missing from instance --></defaultValue[x]>
 <meaningWhenMissing value="[markdown]"/><!--  0..1 Implicit meaning when this element is missing -->
 <fixed[x]><!--  0..1 * Value must be exactly this --></fixed[x]>
 <pattern[x]><!--  0..1 * Value must have at least these property values --></pattern[x]>
 <example[x]><!-- 0..1 * Example value: [as defined for type] --></example[x]>
 <minValue[x]><!-- 0..1 * Minimum Allowed Value (for some types) --></minValue[x]>
 <maxValue[x]><!-- 0..1 * Maximum Allowed Value (for some types) --></maxValue[x]>
 <maxLength value="[integer]"/><!-- 0..1 Max length for strings -->
 <condition value="[id]"/><!-- 0..* Reference to invariant about presence -->
 <constraint>  <!-- 0..* Condition that must evaluate to true -->
  <key value="[id]"/><!--  1..1 Target of 'condition' reference above -->
  <requirements value="[string]"/><!-- 0..1 Why this constraint necessary or appropriate -->
  <severity value="[code]"/><!-- 1..1 error | warning -->
  <human value="[string]"/><!-- 1..1 Human description of constraint -->
  <xpath value="[string]"/><!-- 1..1 XPath expression of constraint -->
 </constraint>
 <mustSupport value="[boolean]"/><!-- 0..1 If the element must supported -->
 <isModifier value="[boolean]"/><!-- 0..1 If this modifies the meaning of other elements -->
 <isSummary value="[boolean]"/><!-- 0..1 Include when _summary = true? -->
 <binding>  <!--  0..1 ValueSet details if this is coded -->
  <strength value="[code]"/><!-- 1..1 required | extensible | preferred | example -->
  <description value="[string]"/><!--  0..1 Human explanation of the value set -->
  <valueSet[x]><!--  0..1 uri|Reference(ValueSet) Source of value set --></valueSet[x]>
 </binding>
 <mapping>  <!-- 0..* Map element to another set of definitions -->
  <identity value="[id]"/><!-- 1..1 Reference to mapping declaration -->
  <language value="[code]"/><!-- 0..1 Computable language of mapping  -->
  <map value="[string]"/><!-- 1..1 Details of the mapping -->
 </mapping>
</[name]>

JSON Template

{
  // from Element: extension
  "path" : "<string>", // R!  The path of the element (see the Detailed Descriptions)
  "representation" : ["<code>"], // How this element is represented in instances
  "name" : "<string>", // Name for this particular element definition (reference target)
  "label" : "<string>", // Name for element to display with or prompt for element
  "code" : [{ Coding }], // Defining code
  "slicing" : { // This element is sliced - slices follow
    "discriminator" : ["<string>"], // Element values that used to distinguish the slices
    "description" : "<string>", // C? Text description of how slicing works (or not)
    "ordered" : <boolean>, // If elements must be in same order as slices
    "rules" : "<code>" // R!  closed | open | openAtEnd
  },
  "short" : "<string>", // Concise definition for xml presentation
  "definition" : "<markdown>", // Full formal definition as narrative text
  "comments" : "<markdown>", // Comments about the use of this element
  "requirements" : "<markdown>", // Why is this needed?
  "alias" : ["<string>"], // Other names
  "min" : <integer>, // C? Minimum Cardinality
  "max" : "<string>", // C? Maximum Cardinality (a number or *)
  "base" : { // Base definition information for tools
    "path" : "<string>", // R!  Path that identifies the base element
    "min" : <integer>, // R!  Min cardinality of the base element
    "max" : "<string>" // R!  Max cardinality of the base element
  },
  "type" : [{ // C? Data type and Profile for this element
    "code" : "<code>", // R!  Name of Data type or Resource
    "profile" : ["<uri>"], // Profile (StructureDefinition) to apply (or IG)
    "aggregation" : ["<code>"] // C? contained | referenced | bundled - how aggregated
  }],
  "nameReference" : "<string>", // C? To another element constraint (by element.name)
  // defaultValue[x]: Specified value it missing from instance. One of these 23:
  "defaultValueInteger" : <integer>,
  "defaultValueDecimal" : <decimal>,
  "defaultValueDateTime" : "<dateTime>",
  "defaultValueDate" : "<date>",
  "defaultValueInstant" : "<instant>",
  "defaultValueString" : "<string>",
  "defaultValueUri" : "<uri>",
  "defaultValueBoolean" : <boolean>,
  "defaultValueCode" : "<code>",
  "defaultValueBase64Binary" : "<base64Binary>",
  "defaultValueCoding" : { Coding },
  "defaultValueCodeableConcept" : { CodeableConcept },
  "defaultValueAttachment" : { Attachment },
  "defaultValueIdentifier" : { Identifier },
  "defaultValueQuantity" : { Quantity },
  "defaultValueRange" : { Range },
  "defaultValuePeriod" : { Period },
  "defaultValueRatio" : { Ratio },
  "defaultValueHumanName" : { HumanName },
  "defaultValueAddress" : { Address },
  "defaultValueContactPoint" : { ContactPoint },
  "defaultValueSchedule" : { Schedule },
  "defaultValueReference" : { Reference },
  "meaningWhenMissing" : "<markdown>", // C? Implicit meaning when this element is missing
  // fixed[x]: Value must be exactly this. One of these 23:
  "fixedInteger" : <integer>,
  "fixedDecimal" : <decimal>,
  "fixedDateTime" : "<dateTime>",
  "fixedDate" : "<date>",
  "fixedInstant" : "<instant>",
  "fixedString" : "<string>",
  "fixedUri" : "<uri>",
  "fixedBoolean" : <boolean>,
  "fixedCode" : "<code>",
  "fixedBase64Binary" : "<base64Binary>",
  "fixedCoding" : { Coding },
  "fixedCodeableConcept" : { CodeableConcept },
  "fixedAttachment" : { Attachment },
  "fixedIdentifier" : { Identifier },
  "fixedQuantity" : { Quantity },
  "fixedRange" : { Range },
  "fixedPeriod" : { Period },
  "fixedRatio" : { Ratio },
  "fixedHumanName" : { HumanName },
  "fixedAddress" : { Address },
  "fixedContactPoint" : { ContactPoint },
  "fixedSchedule" : { Schedule },
  "fixedReference" : { Reference },
  // pattern[x]: Value must have at least these property values. One of these 23:
  "patternInteger" : <integer>,
  "patternDecimal" : <decimal>,
  "patternDateTime" : "<dateTime>",
  "patternDate" : "<date>",
  "patternInstant" : "<instant>",
  "patternString" : "<string>",
  "patternUri" : "<uri>",
  "patternBoolean" : <boolean>,
  "patternCode" : "<code>",
  "patternBase64Binary" : "<base64Binary>",
  "patternCoding" : { Coding },
  "patternCodeableConcept" : { CodeableConcept },
  "patternAttachment" : { Attachment },
  "patternIdentifier" : { Identifier },
  "patternQuantity" : { Quantity },
  "patternRange" : { Range },
  "patternPeriod" : { Period },
  "patternRatio" : { Ratio },
  "patternHumanName" : { HumanName },
  "patternAddress" : { Address },
  "patternContactPoint" : { ContactPoint },
  "patternSchedule" : { Schedule },
  "patternReference" : { Reference },
  // example[x]: Example value: [as defined for type]. One of these 23:
  "exampleInteger" : <integer>,
  "exampleDecimal" : <decimal>,
  "exampleDateTime" : "<dateTime>",
  "exampleDate" : "<date>",
  "exampleInstant" : "<instant>",
  "exampleString" : "<string>",
  "exampleUri" : "<uri>",
  "exampleBoolean" : <boolean>,
  "exampleCode" : "<code>",
  "exampleBase64Binary" : "<base64Binary>",
  "exampleCoding" : { Coding },
  "exampleCodeableConcept" : { CodeableConcept },
  "exampleAttachment" : { Attachment },
  "exampleIdentifier" : { Identifier },
  "exampleQuantity" : { Quantity },
  "exampleRange" : { Range },
  "examplePeriod" : { Period },
  "exampleRatio" : { Ratio },
  "exampleHumanName" : { HumanName },
  "exampleAddress" : { Address },
  "exampleContactPoint" : { ContactPoint },
  "exampleSchedule" : { Schedule },
  "exampleReference" : { Reference },
  // minValue[x]: Minimum Allowed Value (for some types). One of these 23:
  "minValueInteger" : <integer>,
  "minValueDecimal" : <decimal>,
  "minValueDateTime" : "<dateTime>",
  "minValueDate" : "<date>",
  "minValueInstant" : "<instant>",
  "minValueString" : "<string>",
  "minValueUri" : "<uri>",
  "minValueBoolean" : <boolean>,
  "minValueCode" : "<code>",
  "minValueBase64Binary" : "<base64Binary>",
  "minValueCoding" : { Coding },
  "minValueCodeableConcept" : { CodeableConcept },
  "minValueAttachment" : { Attachment },
  "minValueIdentifier" : { Identifier },
  "minValueQuantity" : { Quantity },
  "minValueRange" : { Range },
  "minValuePeriod" : { Period },
  "minValueRatio" : { Ratio },
  "minValueHumanName" : { HumanName },
  "minValueAddress" : { Address },
  "minValueContactPoint" : { ContactPoint },
  "minValueSchedule" : { Schedule },
  "minValueReference" : { Reference },
  // maxValue[x]: Maximum Allowed Value (for some types). One of these 23:
  "maxValueInteger" : <integer>,
  "maxValueDecimal" : <decimal>,
  "maxValueDateTime" : "<dateTime>",
  "maxValueDate" : "<date>",
  "maxValueInstant" : "<instant>",
  "maxValueString" : "<string>",
  "maxValueUri" : "<uri>",
  "maxValueBoolean" : <boolean>,
  "maxValueCode" : "<code>",
  "maxValueBase64Binary" : "<base64Binary>",
  "maxValueCoding" : { Coding },
  "maxValueCodeableConcept" : { CodeableConcept },
  "maxValueAttachment" : { Attachment },
  "maxValueIdentifier" : { Identifier },
  "maxValueQuantity" : { Quantity },
  "maxValueRange" : { Range },
  "maxValuePeriod" : { Period },
  "maxValueRatio" : { Ratio },
  "maxValueHumanName" : { HumanName },
  "maxValueAddress" : { Address },
  "maxValueContactPoint" : { ContactPoint },
  "maxValueSchedule" : { Schedule },
  "maxValueReference" : { Reference },
  "maxLength" : <integer>, // Max length for strings
  "condition" : ["<id>"], // Reference to invariant about presence
  "constraint" : [{ // Condition that must evaluate to true
    "key" : "<id>", // C? R!  Target of 'condition' reference above
    "requirements" : "<string>", // Why this constraint necessary or appropriate
    "severity" : "<code>", // R!  error | warning
    "human" : "<string>", // R!  Human description of constraint
    "xpath" : "<string>" // R!  XPath expression of constraint
  }],
  "mustSupport" : <boolean>, // If the element must supported
  "isModifier" : <boolean>, // If this modifies the meaning of other elements
  "isSummary" : <boolean>, // Include when _summary = true?
  "binding" : { // C? ValueSet details if this is coded
    "strength" : "<code>", // R!  required | extensible | preferred | example
    "description" : "<string>", // C? Human explanation of the value set
    // valueSet[x]: Source of value set. One of these 2:
    "valueSetUri" : "<uri>"
    "valueSetReference" : { Reference(ValueSet) }
  },
  "mapping" : [{ // Map element to another set of definitions
    "identity" : "<id>", // R!  Reference to mapping declaration
    "language" : "<code>", // Computable language of mapping 
    "map" : "<string>" // R!  Details of the mapping
  }]
}

Constraints

eld-1: On ElementDefinition.slicing: If there are no discriminators, there must be a definition (xpath on f:ElementDefinition/f:slicing: (f:discriminator) or (f:description))
eld-10: On ElementDefinition.binding: provide either a reference or a description (or both) (xpath on f:ElementDefinition/f:binding: (exists(f:valueSetUri) or exists(f:valueSetReference)) or exists(f:description))
eld-11: Binding can only be present for coded elements, string, and uri (xpath: not(exists(f:binding)) or (count(f:type/f:code) = 0) or f:type/f:code/@value=('code','Coding','CodeableConcept','Quantity','Extension', 'string', 'uri'))
eld-12: On ElementDefinition.binding.valueSet[x]: URI SHALL start with http:// or https:// (xpath on f:ElementDefinition/f:binding/f:valueSet[x]: starts-with(string(@value), 'http:') or starts-with(string(@value), 'https:'))
eld-13: Types must be unique by the combination of code and profile (xpath: not(exists(for $type in f:type return $type/preceding-sibling::f:type[f:code/@value=$type/f:code/@value and f:profile/@value = $type/f:profile/@value])))
eld-14: Constraints must be unique by key (xpath: count(f:constraint) = count(distinct-values(f:constraint/f:key/@value)))
eld-15: default value and meaningWhenMissing are mutually exclusive (xpath: not(exists(f:*[starts-with(local-name(.), 'fixed')])) or not(exists(f:meaningWhenMissing)))
eld-2: Min <= Max (xpath: not(exists(f:min)) or not(exists(f:max)) or (not(f:max/@value) and not(f:min/@value)) or (f:max/@value = '*') or (number(f:max/@value) >= f:min/@value))
eld-3: On ElementDefinition.max: Max SHALL be a number or "*" (xpath on f:ElementDefinition/f:max: @value='*' or (normalize-space(@value)!='' and normalize-space(translate(@value, '0123456789',''))=''))
eld-4: On ElementDefinition.type: Aggregation may only be specified if one of the allowed types for the element is a resource (xpath on f:ElementDefinition/f:type: not(exists(f:aggregation)) or exists(f:code[@value = 'Reference']))
eld-5: Either a namereference or a fixed value (but not both) is permitted (xpath: not(exists(f:nameReference) and exists(f:*[starts-with(local-name(.), 'value')])))
eld-6: Fixed value may only be specified if there is one type (xpath: not(exists(f:*[starts-with(local-name(.), 'fixed')])) or (count(f:type)=1))
eld-7: Pattern may only be specified if there is one type (xpath: not(exists(f:*[starts-with(local-name(.), 'pattern')])) or (count(f:type)=1))
eld-8: Pattern and value are mutually exclusive (xpath: not(exists(f:*[starts-with(local-name(.), 'pattern')])) or not(exists(f:*[starts-with(local-name(.), 'value')])))

1.23.0.2 Interpretation of ElementDefinition in different contexts

The data type ElementDefinition is used both in StructureDefinition and DataElement, and within those resources, the way its elements are to be used and interpreted depend on the context where ElementDefinition used:

ElementDefinition field

DataElement

Base definition, first element

Base definition, following elements

Constraint Definition, first element

Constraint Definition, following elements

name

prohibited

optional, for profile re-use

slicing

prohibited

optional

short/definition

optional

required

required^‡

requirements/
comments/alias

optional

prohibited

optional

prohibited^‡

optional^‡

base

prohibited

required

nameReference

prohibited

optional

prohibited

optional

defaultValue[x]

optional

prohibited

optional

prohibited

optional^†

meaningWhenMissing

optional

prohibited

optional

prohibited

optional^†

fixed[x]

prohibited

optional

pattern[x]

optional

prohibited

optional

example[x]

optional

prohibited

optional

prohibited

optional

minValue[x]

optional

prohibited

optional

maxValue[x]

optional

prohibited

optional

maxLength

optional

prohibited

optional

mustSupport

optional

prohibited

optional

isModifier

prohibited

optional

prohibited

optional^†

isSummary

prohibited

optional

prohibited

optional^†

binding

optional

prohibited

optional

prohibited

optional

constraint/mapping

optional

prohibited

optional

optional^∆

Notes:

Base definition: A StructureDefinition without a base element - e.g. a definition of a structure that doesn't constrain another structure
Constraint definition: A StructureDefinition with a base element - e.g. a definition of a structure that constrains another base structure
^†: The element's presence, and value, must match the definition in the base structure
^‡: The element content must be consistent with that matching element in the base structure
^∆: Additional constraints and mappings can be defined, but they do not replace the ones in the base structure

The use of Path and type depends more deeply on the context where the ElementDefinition is used:

Context path (1st element) path (following elements) type (1st element)

Data Element Any token Any token (distinct in the DataElement) Any type

Base definition of a data type
(example: Quantity - XML, JSON) Name of the type Path inside the datatype Element

A constrained data type
(example: Money - XML, JSON) Name of the base type Path inside the datatype Name of the base type

Base definition of a resource
(example: Patient - XML, JSON) The name of the resource Path inside the resource DomainResource or sometimes Resource

Constraint on a resource
(example: DAF Patient - XML, JSON) The name of the resource Path inside the resource
(including into the data types) The name of the resource

Base Extension (a standard data type)
(example: Extension - XML, JSON) Extension Extension.value[x] or Extension.extension Extension

A defined Extension
(example: Extension - XML, JSON) Extension Extension.value[x] or Extension.extension (for complex extensions) Extension

1.23.0.2.1 Rules about Slicing

Slicing is only allowed when constraining an existing structure
slicing can only be used on the first repeat of an element, this element is considered the slicing entry
The first entry (the one having the slicing information) is understood to be the set of constraints to be used for the "open" slice. i.e. when the slice is open, this definition is used as a constraint on elements in the instance that are not part of a slice and belong to the open portion of the slice. Its use follows the "normal case", except:
- slicing must be present
- min and max govern the number of total occurrences of the sliced element including the number of occurrences in the open portion of the slice.
An element with a cardinality of 0..1 and a choice of multiple types can be sliced by type. This is in order to specify different constraints for different types. In this case, the discriminator SHALL be "@type"

1.23.0.2.2 Rules about min and max

In a DataElement, min and max are always required.

In a StructureDefinition:

If there is no StructureDefinition.base: min and max are always required
Else, in StructureDefinition.differential: min and max are always optional; if they are not present, they default to the base min and max
and in StructureDefinition.snapshot: min and max are always required

1.23.0.2.3 Missing Elements

Most elements have a minimum cardinality of 0, which means that they may be missing from a resource when it is exchanged between systems. Generally, when an element is missing, all that an application processing the resource can say about the element is that the value is unknown - it may have a correct value, but it has not been provided for security or workflow reasons. On the other hand, it may not have a value at all. All the application can say is that the value is unknown.

However, for some elements, this specification makes specific rules about what it means if the element is missing. For some elements, this takes the form of a default value, a value that should be assumed if on element is present. For example, here are some default values:

Element

Default Value

ElementDefinition.mustSupport

false

SampledData.factor

ValueSet.codeSystem.concept.abstract

false

List.entry.deleted

false

Most default values are mathematical / numerical non-operations e.g. false, 0 for addition or 1 for multiplication. Default values are rarely used because:

The value must be known by all implementations
When an element has a default value, it can never be unknown - e.g. it is implicitly mandatory
The default value can never be changed.

For other elements, the resource explicitly documents what the meaning of a missing element is, and the meaning is not represented by a default value. Some examples:

Element

Meaning when missing

Period.end

If the end of the period is missing, it means that the period is ongoing

Quantity.comparator

If there is no comparator, then there is no modification of the value

MedicationAdministration.wasNotGiven

If this is missing, then the medication was administered

Substance.instance

If this element is not present, then the substance resource describes a kind of substance

Like default values, and for the same reasons, assigning a meaning when an element is missing is something that is not done very often. Note that Profiles cannot change the default value or missing meaning of an element, since it can't be done in the base specification either.