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

This page is part of the FHIR Core Extensions Registry (v0.1.0: Releases Draft) based on FHIR v5.0.0. . For a full list of available versions, see the Directory of published versions

Extension: targetInvariant - Detailed Descriptions

Page standards status: Trial-use

Maturity Level: 1

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.

1. Extension
Definition	Specifies an invariant that is enforced in the context of an instantiated resource. Optional Extension Element - found in all resources.
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.
2. Extension.extension:key
SliceName	key
Definition	A unique identifier for the invariant (unique in the context of the resource).
Control	1..1
Type	Extension
Comments	Any error or outcome messages or warnings should include this id to allow the source of the message to be determined.
3. Extension.extension:key.extension
Control	0..0
4. Extension.extension:key.url
Control	0..?
Type	uri
Fixed Value	key
5. Extension.extension:key.value[x]
Control	1..?
Type	id
[x] Note	See Choice of Data Types for further information about how to use [x]
6. Extension.extension:requirements
SliceName	requirements
Definition	A brief description of why the invariant is necessary or appropriate.
Control	0..1
Type	Extension
7. Extension.extension:requirements.extension
Control	0..0
8. Extension.extension:requirements.url
Control	0..?
Type	uri
Fixed Value	requirements
9. Extension.extension:requirements.value[x]
Control	1..?
Type	string
[x] Note	See Choice of Data Types for further information about how to use [x]
10. Extension.extension:severity
SliceName	severity
Definition	Whether the invariant indicates an error condition or a warning.
Control	1..1
Type	Extension
11. Extension.extension:severity.extension
Control	0..0
12. Extension.extension:severity.url
Control	0..?
Type	uri
Fixed Value	severity
13. Extension.extension:severity.value[x]
Control	1..?
Binding	The codes SHALL be taken from ConstraintSeverity
Type	code
[x] Note	See Choice of Data Types for further information about how to use [x]
14. Extension.extension:expression
SliceName	expression
Definition	An expression providing a formal representation of the invariant condition.
Control	1..1
Type	Extension
Comments	The expression will have access to `%target` (the resource that was instantiated) and `%definition` (the definition for the instantiated resource).
15. Extension.extension:expression.extension
Control	0..0
16. Extension.extension:expression.url
Control	0..?
Type	uri
Fixed Value	expression
17. Extension.extension:expression.value[x]
Control	1..?
Type	Expression
[x] Note	See Choice of Data Types for further information about how to use [x]
18. Extension.url
Fixed Value	http://hl7.org/fhir/StructureDefinition/cqf-targetInvariant
19. Extension.value[x]
Control	0..01
[x] Note	See Choice of Data Types for further information about how to use [x]

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

1. Extension
Definition	Specifies an invariant that is enforced in the context of an instantiated resource. Optional Extension Element - found in all resources.
Control	0..*
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.
Invariants	Defined on this element 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:key
SliceName	key
Definition	A unique identifier for the invariant (unique in the context of the resource). 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.
Control	10..1*
Type	Extension
Summary	false
Alternate Names	extensions, user content
Comments	Any error or outcome messages or warnings should include this id to allow the source of the message to be determined. 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.
Invariants	Defined on this element 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())
3. 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.
Control	0..0*
Type	Extension
Summary	false
Alternate Names	extensions, user content
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.
Invariants	Defined on this element 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 are unordered and Open, and can be differentiated using the following discriminators: value @ url
4. Extension.extension:key.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Control	1..1
Type	uri
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
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.
Fixed Value	key
5. 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).
Control	10..1 This element is affected by the following invariants: ext-1
Type	Choice of: 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]
Summary	false
Invariants	Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count()))
6. Extension.extension:requirements
SliceName	requirements
Definition	A brief description of why the invariant is necessary or appropriate. 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.
Control	0..1*
Type	Extension
Summary	false
Alternate Names	extensions, user content
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.
Invariants	Defined on this element 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())
7. 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.
Control	0..0*
Type	Extension
Summary	false
Alternate Names	extensions, user content
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.
Invariants	Defined on this element 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 are unordered and Open, and can be differentiated using the following discriminators: value @ url
8. Extension.extension:requirements.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Control	1..1
Type	uri
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
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.
Fixed Value	requirements
9. 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).
Control	10..1 This element is affected by the following invariants: ext-1
Type	Choice of: 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]
Summary	false
Invariants	Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count()))
10. Extension.extension:severity
SliceName	severity
Definition	Whether the invariant indicates an error condition or a warning. 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.
Control	10..1*
Type	Extension
Summary	false
Alternate Names	extensions, user content
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.
Invariants	Defined on this element 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())
11. 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.
Control	0..0*
Type	Extension
Summary	false
Alternate Names	extensions, user content
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.
Invariants	Defined on this element 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 are unordered and Open, and can be differentiated using the following discriminators: value @ url
12. Extension.extension:severity.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Control	1..1
Type	uri
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
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.
Fixed Value	severity
13. 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).
Control	10..1 This element is affected by the following invariants: ext-1
Binding	The codes SHALL be taken from ConstraintSeverityFor codes, see (unbound)
Type	Choice of: 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]
Summary	false
Invariants	Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count()))
14. Extension.extension:expression
SliceName	expression
Definition	An expression providing a formal representation of the invariant condition. 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.
Control	10..1*
Type	Extension
Summary	false
Alternate Names	extensions, user content
Comments	The expression will have access to `%target` (the resource that was instantiated) and `%definition` (the definition for the instantiated resource). 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.
Invariants	Defined on this element 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())
15. 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.
Control	0..0*
Type	Extension
Summary	false
Alternate Names	extensions, user content
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.
Invariants	Defined on this element 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 are unordered and Open, and can be differentiated using the following discriminators: value @ url
16. Extension.extension:expression.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Control	1..1
Type	uri
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
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.
Fixed Value	expression
17. 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).
Control	10..1 This element is affected by the following invariants: ext-1
Type	Choice of: 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]
Summary	false
Invariants	Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count()))
18. Extension.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Control	1..1
Type	uri
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
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.
Fixed Value	http://hl7.org/fhir/StructureDefinition/cqf-targetInvariant
19. Extension.value[x]
Definition	Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
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
[x] Note	See Choice of Data Types for further information about how to use [x]
Summary	false
Invariants	Defined on this element 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.

1. Extension
Definition	Specifies an invariant that is enforced in the context of an instantiated resource.
Control	0..*
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.
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.
Control	0..1 This element is affected by the following invariants: ele-1
Type	id
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
3. 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.
Control	0..*
Type	Extension
Summary	false
Alternate Names	extensions, user content
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.
Invariants	Defined on this element 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 are unordered and Open, and can be differentiated using the following discriminators: value @ url
4. Extension.extension:key
SliceName	key
Definition	A unique identifier for the invariant (unique in the context of the resource).
Control	1..1
Type	Extension
Summary	false
Comments	Any error or outcome messages or warnings should include this id to allow the source of the message to be determined.
Invariants	Defined on this element 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())
5. 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.
Control	0..1 This element is affected by the following invariants: ele-1
Type	id
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
6. Extension.extension:key.extension
Definition	An Extension
Control	0..0
Type	Extension
Summary	false
Invariants	Defined on this element 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 are unordered and Open, and can be differentiated using the following discriminators: value @ url
7. Extension.extension:key.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Control	1..1
Type	uri
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
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.
Fixed Value	key
8. 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).
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]
Summary	false
Invariants	Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count()))
9. Extension.extension:requirements
SliceName	requirements
Definition	A brief description of why the invariant is necessary or appropriate.
Control	0..1
Type	Extension
Summary	false
Invariants	Defined on this element 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())
10. 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.
Control	0..1 This element is affected by the following invariants: ele-1
Type	id
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
11. Extension.extension:requirements.extension
Definition	An Extension
Control	0..0
Type	Extension
Summary	false
Invariants	Defined on this element 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 are unordered and Open, and can be differentiated using the following discriminators: value @ url
12. Extension.extension:requirements.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Control	1..1
Type	uri
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
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.
Fixed Value	requirements
13. 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).
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]
Summary	false
Invariants	Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count()))
14. Extension.extension:severity
SliceName	severity
Definition	Whether the invariant indicates an error condition or a warning.
Control	1..1
Type	Extension
Summary	false
Invariants	Defined on this element 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())
15. 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.
Control	0..1 This element is affected by the following invariants: ele-1
Type	id
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
16. Extension.extension:severity.extension
Definition	An Extension
Control	0..0
Type	Extension
Summary	false
Invariants	Defined on this element 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 are unordered and Open, and can be differentiated using the following discriminators: value @ url
17. Extension.extension:severity.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Control	1..1
Type	uri
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
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.
Fixed Value	severity
18. 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).
Control	1..1 This element is affected by the following invariants: ext-1
Binding	The codes SHALL be taken from ConstraintSeverity
Type	code
[x] Note	See Choice of Data Types for further information about how to use [x]
Summary	false
Invariants	Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count()))
19. Extension.extension:expression
SliceName	expression
Definition	An expression providing a formal representation of the invariant condition.
Control	1..1
Type	Extension
Summary	false
Comments	The expression will have access to `%target` (the resource that was instantiated) and `%definition` (the definition for the instantiated resource).
Invariants	Defined on this element 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())
20. 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.
Control	0..1 This element is affected by the following invariants: ele-1
Type	id
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
21. Extension.extension:expression.extension
Definition	An Extension
Control	0..0
Type	Extension
Summary	false
Invariants	Defined on this element 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 are unordered and Open, and can be differentiated using the following discriminators: value @ url
22. Extension.extension:expression.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Control	1..1
Type	uri
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
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.
Fixed Value	expression
23. 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).
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]
Summary	false
Invariants	Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count()))
24. Extension.url
Definition	Source of the definition for the extension code - a logical name or a URL.
Control	1..1
Type	uri
XML Representation	In the XML format, this property is represented as an attribute.
Summary	false
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.
Fixed Value	http://hl7.org/fhir/StructureDefinition/cqf-targetInvariant
25. Extension.value[x]
Definition	Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).
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
[x] Note	See Choice of Data Types for further information about how to use [x]
Summary	false
Invariants	Defined on this element ele-1: All FHIR elements must have a @value or children (: hasValue() or (children().count() > id.count()))