HL7.FHIR.UV.EXTENSIONS\Target invariant - Definitions

This page is part of the FHIR Core Extensions Registry (v5.1.0: Release 5.1) based on FHIR (HL7® FHIR® Standard) v5.0.0. This is the current published version in its permanent home (it will always be available at this URL). For a full list of available versions, see the Directory of published versions

Extension: TargetInvariant - Detailed Descriptions

Page standards status: Deprecated

Maturity Level: 2

Definitions for the cqf-targetInvariant extension.

Differential Elements Table
Key Elements Table
Snapshot Elements Table

Guidance on how to interpret the contents of this table can be found here

0. Extension
Definition	Specifies an invariant that is enforced in the context of an instantiated resource.
Short	A constraint on the target resource
Comments	Can be used on any definitional artifact to define an invariant that is enforced in the context of an instantiated resource. The invariant expression will have access to `%target` and `%definition` variables, where target is the instantiated resource, and definition is the definition used to instantiate.
Control	0..*
2. Extension.extension:key
Slice Name	key
Definition	A unique identifier for the invariant (unique in the context of the resource).
Short	Unique identifier
Comments	Any error or outcome messages or warnings should include this id to allow the source of the message to be determined.
Control	1..1
Type	Extension
4. Extension.extension:key.extension
Control	0..0
6. Extension.extension:key.url
Type	uri
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Fixed Value	`key`
8. Extension.extension:key.value[x]
Control	1..?
Type	id
[x] Note	See Choice of Data Types for further information about how to use [x]
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
10. Extension.extension:requirements
Slice Name	requirements
Definition	A brief description of why the invariant is necessary or appropriate.
Short	Why the invariant is defined
Control	0..1
Type	Extension
12. Extension.extension:requirements.extension
Control	0..0
14. Extension.extension:requirements.url
Type	uri
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Fixed Value	`requirements`
16. Extension.extension:requirements.value[x]
Control	1..?
Type	string
[x] Note	See Choice of Data Types for further information about how to use [x]
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
18. Extension.extension:severity
Slice Name	severity
Definition	Whether the invariant indicates an error condition or a warning.
Short	error \| warning
Control	1..1
Type	Extension
20. Extension.extension:severity.extension
Control	0..0
22. Extension.extension:severity.url
Type	uri
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Fixed Value	`severity`
24. Extension.extension:severity.value[x]
Control	1..?
Binding	The codes SHALL be taken from ConstraintSeverity (required to `http://hl7.org/fhir/ValueSet/constraint-severity`)
Type	code
[x] Note	See Choice of Data Types for further information about how to use [x]
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
26. Extension.extension:expression
Slice Name	expression
Definition	An expression providing a formal representation of the invariant condition.
Short	The invariant expression
Comments	The expression will have access to `%target` (the resource that was instantiated) and `%definition` (the definition for the instantiated resource).
Control	1..1
Type	Extension
28. Extension.extension:expression.extension
Control	0..0
30. Extension.extension:expression.url
Type	uri
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Fixed Value	`expression`
32. Extension.extension:expression.value[x]
Control	1..?
Type	Expression
[x] Note	See Choice of Data Types for further information about how to use [x]
34. Extension.url
Fixed Value	`http://hl7.org/fhir/StructureDefinition/cqf-targetInvariant`
36. Extension.value[x]
Control	0..0

Guidance on how to interpret the contents of this table can be found here

0. Extension
Definition	Specifies an invariant that is enforced in the context of an instantiated resource. Optional Extension Element - found in all resources.
Short	A constraint on the target resourceOptional Extensions Element
Comments	Can be used on any definitional artifact to define an invariant that is enforced in the context of an instantiated resource. The invariant expression will have access to `%target` and `%definition` variables, where target is the instantiated resource, and definition is the definition used to instantiate.
Control	0..*
Is Modifier	false
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
2. Extension.extension
Definition	May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.
Short	Additional content defined by implementations
Comments	There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
Control	Changed:30..*
Type	Extension
Is Modifier	false
Summary	false
Alternate Names	extensions, user content
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
Slicing	This element introduces a set of slices on `Extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
4. Extension.extension:key
Slice Name	key
Definition	A unique identifier for the invariant (unique in the context of the resource).
Short	Unique identifierAdditional content defined by implementations
Comments	Any error or outcome messages or warnings should include this id to allow the source of the message to be determined.
Control	10..1*
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
6. Extension.extension:key.extension
Definition	An Extension May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.
Short	ExtensionAdditional content defined by implementations
Comments	There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
Control	0..0*
Type	Extension
Is Modifier	false
Summary	false
Alternate Names	extensions, user content
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
Slicing	This element introduces a set of slices on `Extension.extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
8. Extension.extension:key.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Short	identifies the meaning of the extension
Comments	The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control	1..1
Type	uri
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
Fixed Value	`key`
10. Extension.extension:key.value[x]
Definition	Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short	Value of extension
Control	10..1 This element is affected by the following invariants: ext-1
Type	id, date, Meta, Address, Attachment, integer, Count, DataRequirement, Dosage, uuid, Identifier, RatioRange, Coding, SampledData, positiveInt, Distance, Availability, integer64, Period, Duration, canonical, Range, RelatedArtifact, base64Binary, UsageContext, Timing, decimal, ExtendedContactDetail, CodeableConcept, ParameterDefinition, dateTime, code, string, oid, instant, ContactPoint, HumanName, Money, markdown, Ratio, Age, Reference, TriggerDefinition, Quantity, uri, url, Annotation, ContactDetail, boolean, Expression, CodeableReference, Signature, unsignedInt, time
[x] Note	See Choice of Data Types for further information about how to use [x]
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
12. Extension.extension:requirements
Slice Name	requirements
Definition	A brief description of why the invariant is necessary or appropriate.
Short	Why the invariant is definedAdditional content defined by implementations
Control	0..1*
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
14. Extension.extension:requirements.extension
Definition	An Extension May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.
Short	ExtensionAdditional content defined by implementations
Comments	There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
Control	0..0*
Type	Extension
Is Modifier	false
Summary	false
Alternate Names	extensions, user content
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
Slicing	This element introduces a set of slices on `Extension.extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
16. Extension.extension:requirements.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Short	identifies the meaning of the extension
Comments	The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control	1..1
Type	uri
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
Fixed Value	`requirements`
18. Extension.extension:requirements.value[x]
Definition	Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short	Value of extension
Control	10..1 This element is affected by the following invariants: ext-1
Type	string, date, Meta, Address, Attachment, integer, Count, DataRequirement, Dosage, uuid, Identifier, RatioRange, Coding, SampledData, id, positiveInt, Distance, Availability, integer64, Period, Duration, canonical, Range, RelatedArtifact, base64Binary, UsageContext, Timing, decimal, ExtendedContactDetail, CodeableConcept, ParameterDefinition, dateTime, code, oid, instant, ContactPoint, HumanName, Money, markdown, Ratio, Age, Reference, TriggerDefinition, Quantity, uri, url, Annotation, ContactDetail, boolean, Expression, CodeableReference, Signature, unsignedInt, time
[x] Note	See Choice of Data Types for further information about how to use [x]
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
20. Extension.extension:severity
Slice Name	severity
Definition	Whether the invariant indicates an error condition or a warning.
Short	error \| warningAdditional content defined by implementations
Control	10..1*
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
22. Extension.extension:severity.extension
Definition	An Extension May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.
Short	ExtensionAdditional content defined by implementations
Comments	There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
Control	0..0*
Type	Extension
Is Modifier	false
Summary	false
Alternate Names	extensions, user content
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
Slicing	This element introduces a set of slices on `Extension.extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
24. Extension.extension:severity.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Short	identifies the meaning of the extension
Comments	The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control	1..1
Type	uri
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
Fixed Value	`severity`
26. Extension.extension:severity.value[x]
Definition	Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short	Value of extension
Control	10..1 This element is affected by the following invariants: ext-1
Binding	The codes SHALL be taken from For codes, see ConstraintSeverity (required to `http://hl7.org/fhir/ValueSet/constraint-severity`)
Type	code, date, Meta, Address, Attachment, integer, Count, DataRequirement, Dosage, uuid, Identifier, RatioRange, Coding, SampledData, id, positiveInt, Distance, Availability, integer64, Period, Duration, canonical, Range, RelatedArtifact, base64Binary, UsageContext, Timing, decimal, ExtendedContactDetail, CodeableConcept, ParameterDefinition, dateTime, string, oid, instant, ContactPoint, HumanName, Money, markdown, Ratio, Age, Reference, TriggerDefinition, Quantity, uri, url, Annotation, ContactDetail, boolean, Expression, CodeableReference, Signature, unsignedInt, time
[x] Note	See Choice of Data Types for further information about how to use [x]
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
28. Extension.extension:expression
Slice Name	expression
Definition	An expression providing a formal representation of the invariant condition.
Short	The invariant expressionAdditional content defined by implementations
Comments	The expression will have access to `%target` (the resource that was instantiated) and `%definition` (the definition for the instantiated resource).
Control	10..1*
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
30. Extension.extension:expression.extension
Definition	An Extension May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.
Short	ExtensionAdditional content defined by implementations
Comments	There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
Control	0..0*
Type	Extension
Is Modifier	false
Summary	false
Alternate Names	extensions, user content
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count())) ext-1: Must have either extensions or value[x], not both (extension.exists() != value.exists())
Slicing	This element introduces a set of slices on `Extension.extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
32. Extension.extension:expression.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Short	identifies the meaning of the extension
Comments	The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control	1..1
Type	uri
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
Fixed Value	`expression`
34. Extension.extension:expression.value[x]
Definition	Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short	Value of extension
Control	10..1 This element is affected by the following invariants: ext-1
Type	Expression, date, Meta, Address, Attachment, integer, Count, DataRequirement, Dosage, uuid, Identifier, RatioRange, Coding, SampledData, id, positiveInt, Distance, Availability, integer64, Period, Duration, canonical, Range, RelatedArtifact, base64Binary, UsageContext, Timing, decimal, ExtendedContactDetail, CodeableConcept, ParameterDefinition, dateTime, code, string, oid, instant, ContactPoint, HumanName, Money, markdown, Ratio, Age, Reference, TriggerDefinition, Quantity, uri, url, Annotation, ContactDetail, boolean, CodeableReference, Signature, unsignedInt, time
[x] Note	See Choice of Data Types for further information about how to use [x]
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))
36. Extension.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Short	identifies the meaning of the extension
Comments	The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control	1..1
Type	uri
Is Modifier	false
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
Fixed Value	`http://hl7.org/fhir/StructureDefinition/cqf-targetInvariant`
38. Extension.value[x]
Definition	Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short	Value of extension
Control	0..01 This element is affected by the following invariants: ext-1
Type	Choice of: base64Binary, boolean, canonical, code, date, dateTime, decimal, id, instant, integer, integer64, markdown, oid, positiveInt, string, time, unsignedInt, uri, url, uuid, Address, Age, Annotation, Attachment, CodeableConcept, CodeableReference, Coding, ContactPoint, Count, Distance, Duration, HumanName, Identifier, Money, Period, Quantity, Range, Ratio, RatioRange, Reference, SampledData, Signature, Timing, ContactDetail, DataRequirement, Expression, ParameterDefinition, RelatedArtifact, TriggerDefinition, UsageContext, Availability, ExtendedContactDetail, Dosage, Meta
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (hasValue() or (children().count() > id.count()))

Guidance on how to interpret the contents of this table can be found here

0. Extension
Definition	Specifies an invariant that is enforced in the context of an instantiated resource.
Short	A constraint on the target resource
Comments	Can be used on any definitional artifact to define an invariant that is enforced in the context of an instantiated resource. The invariant expression will have access to `%target` and `%definition` variables, where target is the instantiated resource, and definition is the definition used to instantiate.
Control	0..*
Is Modifier	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
2. Extension.id
Definition	Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
Short	Unique id for inter-element referencing
Control	0..1 This element is affected by the following invariants: ele-1
Type	id
Is Modifier	false
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
4. Extension.extension
Definition	May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.
Short	Additional content defined by implementations
Comments	There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
Control	Changed:3..*
Type	Extension
Is Modifier	false
Summary	false
Alternate Names	extensions, user content
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
Slicing	This element introduces a set of slices on `Extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
6. Extension.extension:key
Slice Name	key
Definition	A unique identifier for the invariant (unique in the context of the resource).
Short	Unique identifier
Comments	Any error or outcome messages or warnings should include this id to allow the source of the message to be determined.
Control	1..1
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
8. Extension.extension:key.id
Definition	Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
Short	Unique id for inter-element referencing
Control	0..1 This element is affected by the following invariants: ele-1
Type	id
Is Modifier	false
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
10. Extension.extension:key.extension
Definition	An Extension
Short	Extension
Control	0..0
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
Slicing	This element introduces a set of slices on `Extension.extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
12. Extension.extension:key.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Short	identifies the meaning of the extension
Comments	The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control	1..1
Type	uri
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
Fixed Value	`key`
14. Extension.extension:key.value[x]
Definition	Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short	Value of extension
Control	1..1 This element is affected by the following invariants: ext-1
Type	id
[x] Note	See Choice of Data Types for further information about how to use [x]
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`)
16. Extension.extension:requirements
Slice Name	requirements
Definition	A brief description of why the invariant is necessary or appropriate.
Short	Why the invariant is defined
Control	0..1
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
18. Extension.extension:requirements.id
Definition	Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
Short	Unique id for inter-element referencing
Control	0..1 This element is affected by the following invariants: ele-1
Type	id
Is Modifier	false
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
20. Extension.extension:requirements.extension
Definition	An Extension
Short	Extension
Control	0..0
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
Slicing	This element introduces a set of slices on `Extension.extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
22. Extension.extension:requirements.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Short	identifies the meaning of the extension
Comments	The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control	1..1
Type	uri
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
Fixed Value	`requirements`
24. Extension.extension:requirements.value[x]
Definition	Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short	Value of extension
Control	1..1 This element is affected by the following invariants: ext-1
Type	string
[x] Note	See Choice of Data Types for further information about how to use [x]
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`)
26. Extension.extension:severity
Slice Name	severity
Definition	Whether the invariant indicates an error condition or a warning.
Short	error \| warning
Control	1..1
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
28. Extension.extension:severity.id
Definition	Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
Short	Unique id for inter-element referencing
Control	0..1 This element is affected by the following invariants: ele-1
Type	id
Is Modifier	false
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
30. Extension.extension:severity.extension
Definition	An Extension
Short	Extension
Control	0..0
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
Slicing	This element introduces a set of slices on `Extension.extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
32. Extension.extension:severity.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Short	identifies the meaning of the extension
Comments	The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control	1..1
Type	uri
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
Fixed Value	`severity`
34. Extension.extension:severity.value[x]
Definition	Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short	Value of extension
Control	1..1 This element is affected by the following invariants: ext-1
Binding	The codes SHALL be taken from ConstraintSeverity (required to `http://hl7.org/fhir/ValueSet/constraint-severity`)
Type	code
[x] Note	See Choice of Data Types for further information about how to use [x]
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`)
36. Extension.extension:expression
Slice Name	expression
Definition	An expression providing a formal representation of the invariant condition.
Short	The invariant expression
Comments	The expression will have access to `%target` (the resource that was instantiated) and `%definition` (the definition for the instantiated resource).
Control	1..1
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
38. Extension.extension:expression.id
Definition	Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.
Short	Unique id for inter-element referencing
Control	0..1 This element is affected by the following invariants: ele-1
Type	id
Is Modifier	false
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
40. Extension.extension:expression.extension
Definition	An Extension
Short	Extension
Control	0..0
Type	Extension
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`) ext-1: Must have either extensions or value[x], not both (`extension.exists() != value.exists()`)
Slicing	This element introduces a set of slices on `Extension.extension.extension`. The slices areUnordered and Open, and can be differentiated using the following discriminators: value @ url
42. Extension.extension:expression.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Short	identifies the meaning of the extension
Comments	The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control	1..1
Type	uri
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
Fixed Value	`expression`
44. Extension.extension:expression.value[x]
Definition	Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short	Value of extension
Control	1..1 This element is affected by the following invariants: ext-1
Type	Expression
[x] Note	See Choice of Data Types for further information about how to use [x]
Is Modifier	false
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`)
46. Extension.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Short	identifies the meaning of the extension
Comments	The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
Control	1..1
Type	uri
Is Modifier	false
XML Format	In the XML format, this property is represented as an attribute.
Summary	false
Fixed Value	`http://hl7.org/fhir/StructureDefinition/cqf-targetInvariant`
48. Extension.value[x]
Definition	Changed: Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
Short	Value of extension
Control	0..0 This element is affected by the following invariants: ext-1
Type	Choice of: base64Binary, boolean, canonical, code, date, dateTime, decimal, id, instant, integer, integer64, markdown, oid, positiveInt, string, time, unsignedInt, uri, url, uuid, Address, Age, Annotation, Attachment, CodeableConcept, CodeableReference, Coding, ContactPoint, Count, Distance, Duration, HumanName, Identifier, Money, Period, Quantity, Range, Ratio, RatioRange, Reference, SampledData, Signature, Timing, ContactDetail, DataRequirement, Expression, ParameterDefinition, RelatedArtifact, TriggerDefinition, UsageContext, Availability, ExtendedContactDetail, Dosage, Meta
Is Modifier	false
Primitive Value	This primitive element may be present, or absent, or replaced by an extension
Summary	false
Invariants	ele-1: All FHIR elements must have a @value or children (`hasValue() or (children().count() > id.count())`)