Element

Element is a FHIR Schema component which defines or constrains FHIR data type.

Syntax

All properties are optional.

Shape properties

• array (boolean)
• scalar (boolean)

Cardinality properties

• min (integer)
• max (integer)

Choice type properties

• choiceOf (string)
• choices (array of strings)

Requires and exclusions properties

• excluded (array of strings)
• required (array of strings)

Type reference properties

• elementReference (array of strings)
• type (string)

Nested elements property

• elements (object)

Constraints property

• constraints (Constraint)

Slicing property

• slicing (Slicing)

Terminology binding property

• binding (Binding): valueset binding\

Pattern matching (constants definition) property

• fixed (any)
• pattern (any)

Reference target property

• refers (array of strings)

Informational properties

• modifier (boolean)
• mustSupport (boolean)
• summary (boolean)

Shape

There are 2 properties controlling element shape:

• array
• scalar

The array and scalar properties control element structure. These 2 properties are mutually exclusive. I.e. the folowing element is invalid.

array: true
scalar: true

• If array is set, only JSON arrays are accepted.
• If scalar is set, JSON arrays are rejected.
• If neither is set, everything is accepted.

Empty arrays are rejected (they are not allowed by FHIR).

Example

Consider this part of FHIR R4 Core Patient schema:

id: Patient
url: http://hl7.org/fhir/StructureDefinition/Patient
package-meta:
  name: hl7.fhir.r4.core
  version: 4.0.1
  path: "/tmp/lw-fhir-schema-repository/hl7.fhir.r4.core#4.0.1"
base: http://hl7.org/fhir/StructureDefinition/DomainResource
kind: resource
type: Patient
derivation: specialization
elements:
  deceasedBoolean:
    scalar: true
    summary: true
    modifier: true
    type: boolean
    choiceOf: deceased
  maritalStatus:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/marital-status
      strength: extensible
    scalar: true
    type: CodeableConcept
  deceasedDateTime:
    scalar: true
    summary: true
    modifier: true
    type: dateTime
    choiceOf: deceased
  managingOrganization:
    refers:
    - http://hl7.org/fhir/StructureDefinition/Organization
    scalar: true
    summary: true
    type: Reference
  gender:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/administrative-gender
      strength: required
      codesystems:
      - http://hl7.org/fhir/administrative-gender
    type: code
    scalar: true
    summary: true
  multipleBirth:
    choices:
    - multipleBirthBoolean
    - multipleBirthInteger
    scalar: true
  name:
    summary: true
    type: HumanName
    array: true
  address:
    summary: true
    type: Address
    array: true
  identifier:
    summary: true
    type: Identifier
    array: true
  photo:
    type: Attachment
    array: true
  link:
    summary: true
    modifier: true
    required:
    - other
    - type
    type: BackboneElement
    array: true
    elements:
      other:
        refers:
        - http://hl7.org/fhir/StructureDefinition/Patient
        - http://hl7.org/fhir/StructureDefinition/RelatedPerson
        scalar: true
        summary: true
        type: Reference
      type:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/link-type
          strength: required
          codesystems:
          - http://hl7.org/fhir/link-type
        scalar: true
        summary: true
        type: code
  birthDate:
    scalar: true
    summary: true
    type: date
  multipleBirthBoolean:
    scalar: true
    type: boolean
    choiceOf: multipleBirth
  communication:
    required:
    - language
    type: BackboneElement
    array: true
    elements:
      language:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/languages
          strength: preferred
        scalar: true
        type: CodeableConcept
      preferred:
        scalar: true
        type: boolean
  telecom:
    summary: true
    type: ContactPoint
    array: true
  active:
    scalar: true
    summary: true
    modifier: true
    type: boolean
  deceased:
    choices:
    - deceasedBoolean
    - deceasedDateTime
    scalar: true
  generalPractitioner:
    refers:
    - http://hl7.org/fhir/StructureDefinition/Organization
    - http://hl7.org/fhir/StructureDefinition/Practitioner
    - http://hl7.org/fhir/StructureDefinition/PractitionerRole
    type: Reference
    array: true
  contact:
    constraints:
      pat-1:
        human: SHALL at least contain a contact's details or a reference to an organization
        severity: error
        expression: name.exists() or telecom.exists() or address.exists() or organization.exists()
    type: BackboneElement
    array: true
    elements:
      relationship:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/patient-contactrelationship
          strength: extensible
        type: CodeableConcept
        array: true
      name:
        scalar: true
        type: HumanName
      telecom:
        type: ContactPoint
        array: true
      address:
        scalar: true
        type: Address
      gender:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/administrative-gender
          strength: required
          codesystems:
          - http://hl7.org/fhir/administrative-gender
        scalar: true
        type: code
      organization:
        refers:
        - http://hl7.org/fhir/StructureDefinition/Organization
        scalar: true
        type: Reference
      period:
        scalar: true
        type: Period
  multipleBirthInteger:
    scalar: true
    type: integer
    choiceOf: multipleBirth

Resource example that conforms to schema mentioned earlier:

resourceType: Patient
gender: male

resourceType: Patient
name:
  - text: John Smith

Resource example that didn't conform to schema mentioned earlier

resourceType: Patient
gender:
  - male

resourceType: Patient
name:
  text: John Smith

Cardinality

There are 2 properties controlling element cardinality:

• min
• max

Cardinality defines the minimum and maximum number of elements in an array. These properties are allowed only if the shape is set to 'array'.

Absent cardinality property means this cardinality is not restricted. The schema may contain only min or max properties, or it may omit both.

Example

Schema

url: http://example.org/StructureDefinition/patient-minmax
base: http://hl7.org/fhir/StructureDefinition/Patient
type: Patient
derivation: constraint
elements:
  name:
    min: 2
    max: 3

Valid resources

resourceType: Patient
name:
  - text: James
  - text: Mary
meta:
  profile:
    - http://example.org/StructureDefinition/patient-minmax

resourceType: Patient
name:
  - text: James
  - text: Mary
  - text: Robert
meta:
  profile:
    - http://example.org/StructureDefinition/patient-minmax

Invalid resources:

resourceType: Patient
name:
  - text: James
meta:
  profile:
    - http://example.org/StructureDefinition/patient-minmax

resourceType: Patient
name:
  - text: James
  - text: Mary
  - text: Robert
  - text: Patricia
meta:
  profile:
    - http://example.org/StructureDefinition/patient-minmax

Choice type

In FHIR, polymorphic types are used to allow values of different types for specific fields.

resourceType: Patient
multipleBirthBoolean: true

resourceType: Patient
multipleBirthInteger: 2

In the example provided above, multipleBirth[x] is a choice type element, the value of which can either be of the boolean type (multipleBirthBoolean) or the integer type (multipleBirthInteger).

The concurrent presence of the multipleBirthBoolean field and the multipleBirthInteger field in the data is not allowed.

There are 2 properties controlling that polymorphism:

• choices
• choiceOf

choices

This property is intended for the enumeration of available polymorphic type elements.

Example

url: http://example.org/StructureDefinition/patient-choice-type
base: http://hl7.org/fhir/StructureDefinition/Patient
derivation: constraint
elements:
  multipleBirth:
    choices:
      - multipleBirthBoolean
      - multipleBirthInteger
  multipleBirthBoolean:
    choiceOf: multipleBirth
    type: boolean
  multipleBirthInteger:
    type: integer
    choiceOf: multipleBirth

choiceOf

Every concrete polymorphic type element specifies its polymorphic name under the choiceOf property.

Example

url: http://example.org/StructureDefinition/patient-choice-type
base: http://hl7.org/fhir/StructureDefinition/Patient
derivation: constraint
elements:
  multipleBirth:
    choices:
      - multipleBirthBoolean
      - multipleBirthInteger
  multipleBirthBoolean:
    choiceOf: multipleBirth
    type: boolean
  multipleBirthInteger:
    type: integer
    choiceOf: multipleBirth

Valid resources:

resourceType: Patient
meta:
  profile:
    - http://example.org/StructureDefinition/patient-choice-type
multipleBirthBoolean: true

resourceType: Patient
meta:
  profile:
    - http://example.org/StructureDefinition/patient-choice-type
multipleBirthInteger: 3

Invalid resources:

resourceType: Patient
meta:
  profile:
    - http://example.org/StructureDefinition/patient-choice-type
multipleBirthBoolean: true
multipleBirthInteger: 3

resourceType: Patient
meta:
  profile:
    - http://example.org/StructureDefinition/patient-choice-type
multipleBirthString: "3"

resourceType: Patient
meta:
  profile:
    - http://example.org/StructureDefinition/patient-choice-type
multipleBirth: true

resourceType: Patient
meta:
  profile:
    - http://example.org/StructureDefinition/patient-choice-type
multipleBirth: 3

Requires and exclusions

There are 2 elements controlling required and excluded elements:

• required
• excluded

The required property lists all subelements which shall be present. The excluded property lists all subelements which shall be absent.

Example

Schema

url: http://example.org/StructureDefinition/patient-minmax
base: http://hl7.org/fhir/StructureDefinition/Patient
type: Patient
derivation: constraint
required:
  - birthDate
excluded:
  - gender

Valid resources

resourceType: Patient
birthDate: "2000-01-01"
meta:
  profile:
    - http://example.org/StructureDefinition/patient-minmax

resourceType: Patient
birthDate: "2000-01-01"
active: true
meta:
  profile:
    - http://example.org/StructureDefinition/patient-minmax

Invalid resources

resourceType: Patient
active: true
meta:
  profile:
    - http://example.org/StructureDefinition/patient-minmax

resourceType: Patient
gender: other
meta:
  profile:
    - http://example.org/StructureDefinition/patient-minmax

resourceType: Patient
birthDate: "2000-01-01"
gender: other
meta:
  profile:
    - http://example.org/StructureDefinition/patient-minmax

Type reference

There are 2 properties specifying type references:

• type
• elementReference

These two properties are mutually exclusive.

Type reference is either a FHIR type name or canonical URL of the FHIR type.

Base type

The type property specified base type of the element. Data is accepted if both conditions are met:

• Data is accepted when validated against referred type
• Data is accepted by all other conditions on element

Example

Schema

id: Patient
url: http://hl7.org/fhir/StructureDefinition/Patient
package-meta:
  name: hl7.fhir.r4.core
  version: 4.0.1
  path: "/tmp/lw-fhir-schema-repository/hl7.fhir.r4.core#4.0.1"
base: http://hl7.org/fhir/StructureDefinition/DomainResource
kind: resource
type: Patient
derivation: specialization
elements:
  deceasedBoolean:
    scalar: true
    summary: true
    modifier: true
    type: boolean
    choiceOf: deceased
  maritalStatus:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/marital-status
      strength: extensible
    scalar: true
    type: CodeableConcept
  deceasedDateTime:
    scalar: true
    summary: true
    modifier: true
    type: dateTime
    choiceOf: deceased
  managingOrganization:
    refers:
      - http://hl7.org/fhir/StructureDefinition/Organization
    scalar: true
    summary: true
    type: Reference
  gender:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/administrative-gender
      strength: required
      codesystems:
        - http://hl7.org/fhir/administrative-gender
    type: code
    scalar: true
    summary: true
  multipleBirth:
    choices:
      - multipleBirthBoolean
      - multipleBirthInteger
    scalar: true
  name:
    summary: true
    type: HumanName
    array: true
  address:
    summary: true
    type: Address
    array: true
  identifier:
    summary: true
    type: Identifier
    array: true
  photo:
    type: Attachment
    array: true
  link:
    summary: true
    modifier: true
    required:
      - other
      - type
    type: BackboneElement
    array: true
    elements:
      other:
        refers:
          - http://hl7.org/fhir/StructureDefinition/Patient
          - http://hl7.org/fhir/StructureDefinition/RelatedPerson
        scalar: true
        summary: true
        type: Reference
      type:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/link-type
          strength: required
          codesystems:
            - http://hl7.org/fhir/link-type
        scalar: true
        summary: true
        type: code
  birthDate:
    scalar: true
    summary: true
    type: date
  multipleBirthBoolean:
    scalar: true
    type: boolean
    choiceOf: multipleBirth
  communication:
    required:
      - language
    type: BackboneElement
    array: true
    elements:
      language:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/languages
          strength: preferred
        scalar: true
        type: CodeableConcept
      preferred:
        scalar: true
        type: boolean
  telecom:
    summary: true
    type: ContactPoint
    array: true
  active:
    scalar: true
    summary: true
    modifier: true
    type: boolean
  deceased:
    choices:
      - deceasedBoolean
      - deceasedDateTime
    scalar: true
  generalPractitioner:
    refers:
      - http://hl7.org/fhir/StructureDefinition/Organization
      - http://hl7.org/fhir/StructureDefinition/Practitioner
      - http://hl7.org/fhir/StructureDefinition/PractitionerRole
    type: Reference
    array: true
  contact:
    constraints:
      pat-1:
        human: SHALL at least contain a contact's details or a reference to an organization
        severity: error
        expression: name.exists() or telecom.exists() or address.exists() or organization.exists()
    type: BackboneElement
    array: true
    elements:
      relationship:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/patient-contactrelationship
          strength: extensible
        type: CodeableConcept
        array: true
      name:
        scalar: true
        type: HumanName
      telecom:
        type: ContactPoint
        array: true
      address:
        scalar: true
        type: Address
      gender:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/administrative-gender
          strength: required
          codesystems:
            - http://hl7.org/fhir/administrative-gender
        scalar: true
        type: code
      organization:
        refers:
          - http://hl7.org/fhir/StructureDefinition/Organization
        scalar: true
        type: Reference
      period:
        scalar: true
        type: Period
  multipleBirthInteger:
    scalar: true
    type: integer
    choiceOf: multipleBirth
elements:
  a:
    type: string
    array: true
    max: 1
  b:
    type: http://hl7.org/fhir/StructureDefinition/string
    array: true
    max: 1

Valid resources

resourceType: Patient
gender: other

resourceType: Patient
name:
  - text: James

Invalid resources

resourceType: Patient
gender: 2

resourceType: Patient
name:
  - James

resourceType: Patient
gender:
  text: James

resourceType: Patient
name:
  - 2

Element reference syntax

Element reference is an array of the following format:

• First element is a type reference
• Other elements are a path in FHIRSchema

Example

Schema

url: http://example.org/abc
elements:
  a:
    elements:
      b:
        type: string

Element reference referring the b element

[http://example.org/abc, elements, a, elements, b]

Element reference

Data is accepted if both conditions are met:

• Data is accepted when validated against schema for referred element
• Data is accepted by all other conditions on element

Element reference is useful for defining recursive structures (e.g. Questionnaire.item)

Example

Schema

url: http://hl7.org/fhir/StructureDefinition/Questionnaire
constraints:
  que-2:
    human: The link ids for groups and questions must be unique within the questionnaire
    severity: error
    expression: descendants().linkId.isDistinct()
  que-0:
    human: Name should be usable as an identifier for the module by machine processing applications such as code generation
    severity: warning
    expression: name.matches('[A-Z]([A-Za-z0-9_]){0,254}')
package-meta:
  name: hl7.fhir.r4.core
  version: 4.0.1
  path: /tmp/lw-fhir-schema-repository/hl7.fhir.r4.core#4.0.1
id: Questionnaire
base: http://hl7.org/fhir/StructureDefinition/DomainResource
kind: resource
required:
  - status
type: Questionnaire
elements:
  url:
    scalar: true
    summary: true
    type: uri
  derivedFrom:
    refers:
      - http://hl7.org/fhir/StructureDefinition/Questionnaire
    type: canonical
    array: true
  experimental:
    scalar: true
    summary: true
    type: boolean
  effectivePeriod:
    scalar: true
    summary: true
    type: Period
  approvalDate:
    scalar: true
    type: date
  name:
    scalar: true
    summary: true
    type: string
  status:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/publication-status
      strength: required
      codesystems:
        - http://hl7.org/fhir/publication-status
    scalar: true
    summary: true
    modifier: true
    type: code
  identifier:
    summary: true
    type: Identifier
    array: true
  item:
    constraints:
      que-6:
        human: Required and repeat aren't permitted for display items
        severity: error
        expression: type!='display' or (required.empty() and repeats.empty())
      que-3:
        human: Display items cannot have a "code" asserted
        severity: error
        expression: type!='display' or code.empty()
      que-4:
        human: A question cannot have both answerOption and answerValueSet
        severity: error
        expression: answerOption.empty() or answerValueSet.empty()
      que-8:
        human: Initial values can't be specified for groups or display items
        severity: error
        expression: (type!='group' and type!='display') or initial.empty()
      que-13:
        human: Can only have multiple initial values for repeating items
        severity: error
        expression: repeats=true or initial.count() <= 1
      que-12:
        human: If there are more than one enableWhen, enableBehavior must be specified
        severity: error
        expression: enableWhen.count() > 2 implies enableBehavior.exists()
      que-11:
        human: If one or more answerOption is present, initial[x] must be missing
        severity: error
        expression: answerOption.empty() or initial.empty()
      que-9:
        human: Read-only can't be specified for "display" items
        severity: error
        expression: type!='display' or readOnly.empty()
      que-1:
        human: Group items must have nested items, display items cannot have nested items
        severity: error
        expression: (type='group' implies item.empty().not()) and (type.trace('type')='display' implies item.trace('item').empty())
      que-10:
        human: Maximum length can only be declared for simple question types
        severity: error
        expression: (type in ('boolean' | 'decimal' | 'integer' | 'string' | 'text' | 'url' | 'open-choice')) or maxLength.empty()
      que-5:
        human: Only 'choice' and 'open-choice' items can have answerValueSet
        severity: error
        expression: (type ='choice' or type = 'open-choice' or type = 'decimal' or type = 'integer' or type = 'date' or type = 'dateTime' or type = 'time' or type = 'string' or type = 'quantity') or (answerValueSet.empty() and answerOption.empty())
    required:
      - linkId
      - type
    type: BackboneElement
    array: true
    elements:
      answerValueSet:
        refers:
          - http://hl7.org/fhir/StructureDefinition/ValueSet
        scalar: true
        type: canonical
      repeats:
        scalar: true
        type: boolean
      prefix:
        scalar: true
        type: string
      answerOption:
        required:
          - value
          - value
          - value
          - value
          - value
          - value
        type: BackboneElement
        array: true
        elements:
          valueInteger:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: integer
            choiceOf: value
          value:
            choices:
              - valueInteger
              - valueDate
              - valueTime
              - valueString
              - valueCoding
              - valueReference
            scalar: true
          valueDate:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: date
            choiceOf: value
          valueTime:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: time
            choiceOf: value
          valueString:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: string
            choiceOf: value
          valueCoding:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: Coding
            choiceOf: value
          valueReference:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            refers:
              - http://hl7.org/fhir/StructureDefinition/Resource
            scalar: true
            required-element: true
            type: Reference
            choiceOf: value
          initialSelected:
            scalar: true
            type: boolean
      maxLength:
        scalar: true
        type: integer
      initial:
        required:
          - value
          - value
          - value
          - value
          - value
          - value
          - value
          - value
          - value
          - value
          - value
          - value
        type: BackboneElement
        array: true
        elements:
          valueCoding:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: Coding
            choiceOf: value
          valueUri:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: uri
            choiceOf: value
          valueString:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: string
            choiceOf: value
          valueReference:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            refers:
              - http://hl7.org/fhir/StructureDefinition/Resource
            scalar: true
            required-element: true
            type: Reference
            choiceOf: value
          valueDecimal:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: decimal
            choiceOf: value
          valueAttachment:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: Attachment
            choiceOf: value
          valueDateTime:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: dateTime
            choiceOf: value
          value:
            choices:
              - valueBoolean
              - valueDecimal
              - valueInteger
              - valueDate
              - valueDateTime
              - valueTime
              - valueString
              - valueUri
              - valueAttachment
              - valueCoding
              - valueQuantity
              - valueReference
            scalar: true
          valueBoolean:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: boolean
            choiceOf: value
          valueDate:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: date
            choiceOf: value
          valueTime:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: time
            choiceOf: value
          valueQuantity:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: Quantity
            choiceOf: value
          valueInteger:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: integer
            choiceOf: value
      enableWhen:
        constraints:
          que-7:
            human: If the operator is 'exists', the value must be a boolean
            severity: error
            expression: operator = 'exists' implies (answer is Boolean)
        modifier: true
        required:
          - question
          - operator
          - answer
          - answer
          - answer
          - answer
          - answer
          - answer
          - answer
          - answer
          - answer
          - answer
        type: BackboneElement
        array: true
        elements:
          answerReference:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            refers:
              - http://hl7.org/fhir/StructureDefinition/Resource
            scalar: true
            required-element: true
            type: Reference
            choiceOf: answer
          operator:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-enable-operator
              strength: required
              codesystems:
                - http://hl7.org/fhir/questionnaire-enable-operator
            scalar: true
            type: code
          answerDate:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: date
            choiceOf: answer
          answerTime:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: time
            choiceOf: answer
          answerString:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: string
            choiceOf: answer
          answerCoding:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: Coding
            choiceOf: answer
          question:
            scalar: true
            type: string
          answerInteger:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: integer
            choiceOf: answer
          answerQuantity:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: Quantity
            choiceOf: answer
          answerDateTime:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: dateTime
            choiceOf: answer
          answerBoolean:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: boolean
            choiceOf: answer
          answerDecimal:
            binding:
              valueSet: http://hl7.org/fhir/ValueSet/questionnaire-answers
              strength: example
            scalar: true
            required-element: true
            type: decimal
            choiceOf: answer
          answer:
            choices:
              - answerBoolean
              - answerDecimal
              - answerInteger
              - answerDate
              - answerDateTime
              - answerTime
              - answerString
              - answerCoding
              - answerQuantity
              - answerReference
            scalar: true
      text:
        scalar: true
        type: string
      item:
        elementReference:
          - http://hl7.org/fhir/StructureDefinition/Questionnaire
          - elements
          - item
        array: true
      enableBehavior:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/questionnaire-enable-behavior
          strength: required
          codesystems:
            - http://hl7.org/fhir/questionnaire-enable-behavior
        scalar: true
        type: code
      definition:
        scalar: true
        type: uri
      readOnly:
        scalar: true
        type: boolean
      required:
        scalar: true
        type: boolean
      type:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/item-type
          strength: required
          codesystems:
            - http://hl7.org/fhir/item-type
        scalar: true
        type: code
      linkId:
        scalar: true
        type: string
      code:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/questionnaire-questions
          strength: example
        type: Coding
        array: true
  jurisdiction:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/jurisdiction
      strength: extensible
    summary: true
    type: CodeableConcept
    array: true
  title:
    scalar: true
    summary: true
    type: string
  copyright:
    scalar: true
    type: markdown
  publisher:
    scalar: true
    summary: true
    type: string
  version:
    scalar: true
    summary: true
    type: string
  date:
    scalar: true
    summary: true
    type: dateTime
  subjectType:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/resource-types
      strength: required
      codesystems:
        - http://hl7.org/fhir/resource-types
    summary: true
    type: code
    array: true
  useContext:
    summary: true
    type: UsageContext
    array: true
  lastReviewDate:
    scalar: true
    type: date
  code:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/questionnaire-questions
      strength: example
    summary: true
    type: Coding
    array: true
  contact:
    summary: true
    type: ContactDetail
    array: true
  description:
    scalar: true
    type: markdown
  purpose:
    scalar: true
    type: markdown
derivation: specialization

Valid resources:

resourceType: Questionnaire
status: draft
item:
  - type: display
    linkId: q-1

resourceType: Questionnaire
status: draft
item:
  - item:
      - type: display
        linkId: q-2
    type: group
    linkId: q-1

resourceType: Questionnaire
status: draft
item:
  - item:
      - item:
          - item:
              - type: display
                linkId: q-4
            linkId: q-3
            type: group
        linkId: q-2
        type: group
    linkId: q-1
    type: group

Invalid resources:

resourceType: Questionnaire
status: draft
item:
  - item:
      - wrongType
    type: group
    linkId: q-1

resourceType: Questionnaire
status: draft
item:
  - item:
      - item:
          - nonExistentField: abc
            linkId: q-3
            type: group
        linkId: q-2
        type: group
    linkId: q-1
    type: group

Nested elements

The elements property define nested element constraints. Syntactically it is an object, with string keys and Element values. Semantically it defines behavior of the corresponding fields in data.

Example

Schema

id: Patient
url: http://hl7.org/fhir/StructureDefinition/Patient
package-meta:
  name: hl7.fhir.r4.core
  version: 4.0.1
  path: "/tmp/lw-fhir-schema-repository/hl7.fhir.r4.core#4.0.1"
base: http://hl7.org/fhir/StructureDefinition/DomainResource
kind: resource
type: Patient
derivation: specialization
elements:
  deceasedBoolean:
    scalar: true
    summary: true
    modifier: true
    type: boolean
    choiceOf: deceased
  maritalStatus:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/marital-status
      strength: extensible
    scalar: true
    type: CodeableConcept
  deceasedDateTime:
    scalar: true
    summary: true
    modifier: true
    type: dateTime
    choiceOf: deceased
  managingOrganization:
    refers:
      - http://hl7.org/fhir/StructureDefinition/Organization
    scalar: true
    summary: true
    type: Reference
  gender:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/administrative-gender
      strength: required
      codesystems:
        - http://hl7.org/fhir/administrative-gender
    type: code
    scalar: true
    summary: true
  multipleBirth:
    choices:
      - multipleBirthBoolean
      - multipleBirthInteger
    scalar: true
  name:
    summary: true
    type: HumanName
    array: true
  address:
    summary: true
    type: Address
    array: true
  identifier:
    summary: true
    type: Identifier
    array: true
  photo:
    type: Attachment
    array: true
  link:
    summary: true
    modifier: true
    required:
      - other
      - type
    type: BackboneElement
    array: true
    elements:
      other:
        refers:
          - http://hl7.org/fhir/StructureDefinition/Patient
          - http://hl7.org/fhir/StructureDefinition/RelatedPerson
        scalar: true
        summary: true
        type: Reference
      type:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/link-type
          strength: required
          codesystems:
            - http://hl7.org/fhir/link-type
        scalar: true
        summary: true
        type: code
  birthDate:
    scalar: true
    summary: true
    type: date
  multipleBirthBoolean:
    scalar: true
    type: boolean
    choiceOf: multipleBirth
  communication:
    required:
      - language
    type: BackboneElement
    array: true
    elements:
      language:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/languages
          strength: preferred
        scalar: true
        type: CodeableConcept
      preferred:
        scalar: true
        type: boolean
  telecom:
    summary: true
    type: ContactPoint
    array: true
  active:
    scalar: true
    summary: true
    modifier: true
    type: boolean
  deceased:
    choices:
      - deceasedBoolean
      - deceasedDateTime
    scalar: true
  generalPractitioner:
    refers:
      - http://hl7.org/fhir/StructureDefinition/Organization
      - http://hl7.org/fhir/StructureDefinition/Practitioner
      - http://hl7.org/fhir/StructureDefinition/PractitionerRole
    type: Reference
    array: true
  contact:
    constraints:
      pat-1:
        human: SHALL at least contain a contact's details or a reference to an organization
        severity: error
        expression: name.exists() or telecom.exists() or address.exists() or organization.exists()
    type: BackboneElement
    array: true
    elements:
      relationship:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/patient-contactrelationship
          strength: extensible
        type: CodeableConcept
        array: true
      name:
        scalar: true
        type: HumanName
      telecom:
        type: ContactPoint
        array: true
      address:
        scalar: true
        type: Address
      gender:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/administrative-gender
          strength: required
          codesystems:
            - http://hl7.org/fhir/administrative-gender
        scalar: true
        type: code
      organization:
        refers:
          - http://hl7.org/fhir/StructureDefinition/Organization
        scalar: true
        type: Reference
      period:
        scalar: true
        type: Period
  multipleBirthInteger:
    scalar: true
    type: integer
    choiceOf: multipleBirth

Valid resource

resourceType: Patient
link: 
  - other: 
      reference: http://example.org/patient-path
      type: Patient
    type: refer

Invalid resource

resourceType: Patient
link: 
  - unexisting: true

Terminology binding

Syntax

• valueSet (string)
• strength (string)

FHIRSchema terminology binding follows FHIR terminology binding. Both valueSet and strength properties shall be specified.

The valueSet property is a canonical URL referring to the ValueSet to which the codes in the data element value are bound. The strength property specifies FHIR ValueSet binding strength. Only required bindings are validated.

Example

Schema

id: Patient
url: http://hl7.org/fhir/StructureDefinition/Patient
package-meta:
  name: hl7.fhir.r4.core
  version: 4.0.1
  path: "/tmp/lw-fhir-schema-repository/hl7.fhir.r4.core#4.0.1"
base: http://hl7.org/fhir/StructureDefinition/DomainResource
kind: resource
type: Patient
derivation: specialization
elements:
  deceasedBoolean:
    scalar: true
    summary: true
    modifier: true
    type: boolean
    choiceOf: deceased
  maritalStatus:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/marital-status
      strength: extensible
    scalar: true
    type: CodeableConcept
  deceasedDateTime:
    scalar: true
    summary: true
    modifier: true
    type: dateTime
    choiceOf: deceased
  managingOrganization:
    refers:
      - http://hl7.org/fhir/StructureDefinition/Organization
    scalar: true
    summary: true
    type: Reference
  gender:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/administrative-gender
      strength: required
      codesystems:
        - http://hl7.org/fhir/administrative-gender
    type: code
    scalar: true
    summary: true
  multipleBirth:
    choices:
      - multipleBirthBoolean
      - multipleBirthInteger
    scalar: true
  name:
    summary: true
    type: HumanName
    array: true
  address:
    summary: true
    type: Address
    array: true
  identifier:
    summary: true
    type: Identifier
    array: true
  photo:
    type: Attachment
    array: true
  link:
    summary: true
    modifier: true
    required:
      - other
      - type
    type: BackboneElement
    array: true
    elements:
      other:
        refers:
          - http://hl7.org/fhir/StructureDefinition/Patient
          - http://hl7.org/fhir/StructureDefinition/RelatedPerson
        scalar: true
        summary: true
        type: Reference
      type:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/link-type
          strength: required
          codesystems:
            - http://hl7.org/fhir/link-type
        scalar: true
        summary: true
        type: code
  birthDate:
    scalar: true
    summary: true
    type: date
  multipleBirthBoolean:
    scalar: true
    type: boolean
    choiceOf: multipleBirth
  communication:
    required:
      - language
    type: BackboneElement
    array: true
    elements:
      language:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/languages
          strength: preferred
        scalar: true
        type: CodeableConcept
      preferred:
        scalar: true
        type: boolean
  telecom:
    summary: true
    type: ContactPoint
    array: true
  active:
    scalar: true
    summary: true
    modifier: true
    type: boolean
  deceased:
    choices:
      - deceasedBoolean
      - deceasedDateTime
    scalar: true
  generalPractitioner:
    refers:
      - http://hl7.org/fhir/StructureDefinition/Organization
      - http://hl7.org/fhir/StructureDefinition/Practitioner
      - http://hl7.org/fhir/StructureDefinition/PractitionerRole
    type: Reference
    array: true
  contact:
    constraints:
      pat-1:
        human: SHALL at least contain a contact's details or a reference to an organization
        severity: error
        expression: name.exists() or telecom.exists() or address.exists() or organization.exists()
    type: BackboneElement
    array: true
    elements:
      relationship:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/patient-contactrelationship
          strength: extensible
        type: CodeableConcept
        array: true
      name:
        scalar: true
        type: HumanName
      telecom:
        type: ContactPoint
        array: true
      address:
        scalar: true
        type: Address
      gender:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/administrative-gender
          strength: required
          codesystems:
            - http://hl7.org/fhir/administrative-gender
        scalar: true
        type: code
      organization:
        refers:
          - http://hl7.org/fhir/StructureDefinition/Organization
        scalar: true
        type: Reference
      period:
        scalar: true
        type: Period
  multipleBirthInteger:
    scalar: true
    type: integer
    choiceOf: multipleBirth

Note: there is a codesystems property in expanded view of the example schema: it is a technical field generated by StructureDefinition to FHIRSchema conversion, this field speeds up schema loading, but is irrelevant to writing new schemas.

Valid resource:

resourceType: Patient
gender: other

Invalid resource:

resourceType: Patient
gender: something-not-in-the-valueset

Reference target

The refers property lists allows reference targets. A reference data element is accepted only if it refers to one of the allowed here types. A target can be either resource type or canonical URL for this resource type.

Example

Schema:

id: Patient
url: http://hl7.org/fhir/StructureDefinition/Patient
package-meta:
  name: hl7.fhir.r4.core
  version: 4.0.1
  path: "/tmp/lw-fhir-schema-repository/hl7.fhir.r4.core#4.0.1"
base: http://hl7.org/fhir/StructureDefinition/DomainResource
kind: resource
type: Patient
derivation: specialization
elements:
  deceasedBoolean:
    scalar: true
    summary: true
    modifier: true
    type: boolean
    choiceOf: deceased
  maritalStatus:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/marital-status
      strength: extensible
    scalar: true
    type: CodeableConcept
  deceasedDateTime:
    scalar: true
    summary: true
    modifier: true
    type: dateTime
    choiceOf: deceased
  managingOrganization:
    refers:
      - http://hl7.org/fhir/StructureDefinition/Organization
    scalar: true
    summary: true
    type: Reference
  gender:
    binding:
      valueSet: http://hl7.org/fhir/ValueSet/administrative-gender
      strength: required
      codesystems:
        - http://hl7.org/fhir/administrative-gender
    type: code
    scalar: true
    summary: true
  multipleBirth:
    choices:
      - multipleBirthBoolean
      - multipleBirthInteger
    scalar: true
  name:
    summary: true
    type: HumanName
    array: true
  address:
    summary: true
    type: Address
    array: true
  identifier:
    summary: true
    type: Identifier
    array: true
  photo:
    type: Attachment
    array: true
  link:
    summary: true
    modifier: true
    required:
      - other
      - type
    type: BackboneElement
    array: true
    elements:
      other:
        refers:
          - http://hl7.org/fhir/StructureDefinition/Patient
          - http://hl7.org/fhir/StructureDefinition/RelatedPerson
        scalar: true
        summary: true
        type: Reference
      type:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/link-type
          strength: required
          codesystems:
            - http://hl7.org/fhir/link-type
        scalar: true
        summary: true
        type: code
  birthDate:
    scalar: true
    summary: true
    type: date
  multipleBirthBoolean:
    scalar: true
    type: boolean
    choiceOf: multipleBirth
  communication:
    required:
      - language
    type: BackboneElement
    array: true
    elements:
      language:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/languages
          strength: preferred
        scalar: true
        type: CodeableConcept
      preferred:
        scalar: true
        type: boolean
  telecom:
    summary: true
    type: ContactPoint
    array: true
  active:
    scalar: true
    summary: true
    modifier: true
    type: boolean
  deceased:
    choices:
      - deceasedBoolean
      - deceasedDateTime
    scalar: true
  generalPractitioner:
    refers:
      - http://hl7.org/fhir/StructureDefinition/Organization
      - http://hl7.org/fhir/StructureDefinition/Practitioner
      - http://hl7.org/fhir/StructureDefinition/PractitionerRole
    type: Reference
    array: true
  contact:
    constraints:
      pat-1:
        human: SHALL at least contain a contact's details or a reference to an organization
        severity: error
        expression: name.exists() or telecom.exists() or address.exists() or organization.exists()
    type: BackboneElement
    array: true
    elements:
      relationship:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/patient-contactrelationship
          strength: extensible
        type: CodeableConcept
        array: true
      name:
        scalar: true
        type: HumanName
      telecom:
        type: ContactPoint
        array: true
      address:
        scalar: true
        type: Address
      gender:
        binding:
          valueSet: http://hl7.org/fhir/ValueSet/administrative-gender
          strength: required
          codesystems:
            - http://hl7.org/fhir/administrative-gender
        scalar: true
        type: code
      organization:
        refers:
          - http://hl7.org/fhir/StructureDefinition/Organization
        scalar: true
        type: Reference
      period:
        scalar: true
        type: Period
  multipleBirthInteger:
    scalar: true
    type: integer
    choiceOf: multipleBirth

Valid resources:

resourceType: Patient
generalPractitioner:
  - reference: Organization/organization-1

resourceType: Patient
generalPractitioner:
  - reference: Practitioner/practitioner-1
  - reference: Organization/organization-1

resourceType: Patient
generalPractitioner:
  - reference: Practitioner/practitioner-1

Invalid resources:

resourceType: Patient
generalPractitioner:
  - reference: Patient/patient-1

resourceType: Patient
generalPractitioner:
  - reference: Organization/organization-1
  - reference: Patient/patient-1

Pattern matching

There are 2 properties to define elements that match constant values:

• fixed: a value that must match the value of element;
• pattern: a value that specifies the entries or items that an element must contain.

Example

Schema with fixed element

url:  http://example.com/Patient/patient
base: http://hl7.org/fhir/StructureDefinition/Patient
type: Patient
name: Patient-fixed
elements:
  gender:
    type: code
    fixed: male
  name:
    type: HumanName
    fixed:
      - family: Smith

Valid resources

meta:
  profile: 
     - http://example.com/Patient/patient|1.0.0
resourceType: Patient
gender: male
name:
  - family: Smith

Invalid resources

meta:
  profile: 
    - http://example.com/Patient/patient|1.0.0
resourceType: Patient
gender: male
name:
  - family: Smith
    given: John

meta:
  profile: 
    - http://example.com/Patient/patient|1.0.0
resourceType: Patient
gender: female
name:
  - family: Smith

meta:
  profile: 
    - http://example.com/Patient/patient|1.0.0
resourceType: Patient
gender: male
name:
  - family: Smith
    given: John

meta:
  profile: 
    - http://example.com/Patient/patient|1.0.0
resourceType: Patient
gender: male
name:
  - family: Smith
  - family: Gray

Schema with pattern element

url:  http://example.com/Patient/patient
base: http://hl7.org/fhir/StructureDefinition/Patient
type: Patient
name: Patient-pattern
elements:
  gender: 
    type: code
    pattern: male
  name:
    type: HumanName
    pattern:
      - family: Smith

Valid resources

meta:
  profile: 
    - http://example.com/Patient/patient|1.0.0
resourceType: Patient
gender: male
name:
  - family: Smith

meta:
  profile: 
    - http://example.com/Patient/patient|1.0.0
resourceType: Patient
gender: male
name:
  - family: Smith
    given: John

meta:
  profile: 
    - http://example.com/Patient/patient|1.0.0
resourceType: Patient
gender: male
name:
  - family: Smith
  - family: Gray

Invalid resources

meta:
  profile: 
    - http://example.com/Patient/patient|1.0.0
resourceType: Patient
gender: female
name:
  - family: Smith

meta:
  profile: 
    - http://example.com/Patient/patient|1.0.0
resourceType: Patient
gender: male
name:
  - family: Gray

Informational

These properties do not affect validation, but they provide additional information about element.

The modifier property mirrors the ElementDefinition.isModifier FHIR property. The modifier element changes the interpretation of the resource.

The mustSupport property mirrors the ElementDefinition.mustSupport FHIR property. The mustSupport element must be supported by an implementation.

The summary property mirrors the ElementDefinition.isSummary FHIR property. The summary element should be included in FHIR Search in summary mode.