description: Specifies a constraint that is enforced on instantiated (or target) resources. This extension can be applied to definitional resources (such as ActivityDefinition or Measure) and indicates that the constraint should be enforced on resources that are instantiated from the definition. For example, this extension can be used to define a constraint such as `numerator count must be less than or equal to denominator count`.
package_name: hl7.fhir.uv.extensions.r4
derivation: constraint
name: TargetConstraint
type: Extension
elements:
  extension:
    short: Unique identifier
    type: Extension
    index: 0
    slicing:
      slices:
        key:
          match: {}
          schema:
            short: Unique identifier
            type: Extension
            _required: true
            index: 0
            extensions: {}
            elements:
              extension: {index: 1}
              url:
                type: uri
                pattern: {type: uri, value: key}
                index: 2
              value:
                choices: [valueId]
                index: 4
              valueId: {type: id, choiceOf: value, index: 5}
            required: [value, valueId]
        requirements:
          match: {}
          schema:
            type: Extension
            short: Why the constraint is defined
            index: 6
            extensions: {}
            elements:
              extension: {index: 7}
              url:
                type: uri
                pattern: {type: uri, value: requirements}
                index: 8
              value:
                choices: [valueMarkdown]
                index: 10
              valueMarkdown: {type: markdown, choiceOf: value, index: 11}
            required: [value, valueMarkdown]
        severity:
          match: {}
          schema:
            type: Extension
            short: error | warning
            _required: true
            index: 12
            extensions: {}
            elements:
              extension: {index: 13}
              url:
                type: uri
                pattern: {type: uri, value: severity}
                index: 14
              value:
                choices: [valueCode]
                index: 16
              valueCode: {type: code, choiceOf: value, index: 17}
            required: [value, valueCode]
        expression:
          match: {}
          schema:
            short: The invariant expression
            type: Extension
            _required: true
            index: 18
            extensions: {}
            elements:
              extension: {index: 19}
              url:
                type: uri
                pattern: {type: uri, value: expression}
                index: 20
              value:
                choices: [valueExpression]
                index: 22
              valueExpression: {type: Expression, choiceOf: value, index: 23}
            required: [value, valueExpression]
        human:
          match: {}
          schema:
            type: Extension
            short: Human-readable rule
            _required: true
            index: 24
            extensions: {}
            elements:
              extension: {index: 25}
              url:
                type: uri
                pattern: {type: uri, value: human}
                index: 26
              value:
                choices: [valueString]
                index: 28
              valueString: {type: string, choiceOf: value, index: 29}
            required: [value, valueString]
        location:
          match: {}
          schema:
            type: Extension
            short: Relative path to elements
            array: true
            index: 30
            extensions: {}
            elements:
              extension: {index: 31}
              url:
                type: uri
                pattern: {type: uri, value: location}
                index: 32
              value:
                choices: [valueString]
                index: 34
              valueString: {type: string, choiceOf: value, index: 35}
            required: [value, valueString]
  url:
    pattern: {type: uri, value: 'http://hl7.org/fhir/StructureDefinition/targetConstraint'}
    type: uri
    index: 36
  value:
    choices: []
    index: 38
package_version: 5.3.0-ballot-tc1
extensions:
  key:
    url: null
    short: Unique identifier
    type: Extension
    _required: true
    index: 0
    extensions: {}
    elements:
      extension: {index: 1}
      url:
        type: uri
        pattern: {type: uri, value: key}
        index: 2
      value:
        choices: [valueId]
        index: 4
      valueId: {type: id, choiceOf: value, index: 5}
    required: [value, valueId]
  requirements:
    url: null
    type: Extension
    short: Why the constraint is defined
    index: 6
    extensions: {}
    elements:
      extension: {index: 7}
      url:
        type: uri
        pattern: {type: uri, value: requirements}
        index: 8
      value:
        choices: [valueMarkdown]
        index: 10
      valueMarkdown: {type: markdown, choiceOf: value, index: 11}
    required: [value, valueMarkdown]
  severity:
    url: null
    type: Extension
    short: error | warning
    _required: true
    index: 12
    extensions: {}
    elements:
      extension: {index: 13}
      url:
        type: uri
        pattern: {type: uri, value: severity}
        index: 14
      value:
        choices: [valueCode]
        index: 16
      valueCode: {type: code, choiceOf: value, index: 17}
    required: [value, valueCode]
  expression:
    url: null
    short: The invariant expression
    type: Extension
    _required: true
    index: 18
    extensions: {}
    elements:
      extension: {index: 19}
      url:
        type: uri
        pattern: {type: uri, value: expression}
        index: 20
      value:
        choices: [valueExpression]
        index: 22
      valueExpression: {type: Expression, choiceOf: value, index: 23}
    required: [value, valueExpression]
  human:
    url: null
    type: Extension
    short: Human-readable rule
    _required: true
    index: 24
    extensions: {}
    elements:
      extension: {index: 25}
      url:
        type: uri
        pattern: {type: uri, value: human}
        index: 26
      value:
        choices: [valueString]
        index: 28
      valueString: {type: string, choiceOf: value, index: 29}
    required: [value, valueString]
  location:
    url: null
    type: Extension
    short: Relative path to elements
    array: true
    index: 30
    extensions: {}
    elements:
      extension: {index: 31}
      url:
        type: uri
        pattern: {type: uri, value: location}
        index: 32
      value:
        choices: [valueString]
        index: 34
      valueString: {type: string, choiceOf: value, index: 35}
    required: [value, valueString]
class: extension
kind: complex-type
url: http://hl7.org/fhir/StructureDefinition/targetConstraint
base: http://hl7.org/fhir/StructureDefinition/Extension
version: 5.3.0-ballot-tc1
required: [extension]