eHealth Infrastructure (v2020.8)

StructureDefinition: ehealth-definedquestion - Detailed Descriptions

Definitions for the ehealth-definedquestion Profile.

1. StructureDefinition
Definition

A definition of a FHIR structure. This resource is used to describe the underlying resources, data types defined in FHIR, and also for describing extensions and constraints on resources and data types.

Control0..*
Alternate NamesTemplate, Profile
InvariantsDefined on this element
dom-1: If the resource is contained in another resource, it SHALL NOT contain any narrative (: contained.text.empty())
dom-2: If the resource is contained in another resource, it SHALL NOT contain nested Resources (: contained.contained.empty())
dom-3: If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource (: contained.where(('#'+id in %resource.descendants().reference).not()).empty())
dom-4: If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated (: contained.meta.versionId.empty() and contained.meta.lastUpdated.empty())
sdf-1: Element paths must be unique unless the structure is a constraint (: derivation = 'constraint' or snapshot.element.select(path).isDistinct())
sdf-11: If there's a type, its content must match the path name in the first element of a snapshot (: snapshot.empty() or snapshot.element.first().path = type)
sdf-14: All element definitions must have an id (: snapshot.element.all(id.exists()) and differential.element.all(id.exists()))
sdf-16: All element definitions must have unique ids (snapshot) (: snapshot.element.id.trace('ids').isDistinct())
sdf-17: All element definitions must have unique ids (diff) (: differential.element.id.trace('ids').isDistinct())
sdf-18: Context Invariants can only be used for extensions (: contextInvariant.exists() implies type = 'Extension')
sdf-19: Custom types can only be used in logical models (: kind = 'logical' or (differential.element.type.code.all(hasValue() implies matches('^[a-zA-Z0-9]+$')) and snapshot.element.type.code.all(hasValue() implies matches('^[a-zA-Z0-9]+$'))))
sdf-4: If the structure is not abstract, then there SHALL be a baseDefinition (: abstract = true or baseDefinition.exists())
sdf-5: If the structure defines an extension then the structure must have context information (: type != 'Extension' or derivation = 'specialization' or (context.exists() and contextType.exists()))
sdf-6: A structure must have either a differential, or a snapshot (or both) (: snapshot.exists() or differential.exists())
sdf-7: If the structure describes a base Resource or Type, the URL has to start with "http://hl7.org/fhir/StructureDefinition/" and the tail must match the id (: (derivation = 'constraint') or (kind = 'logical') or (url = 'http://hl7.org/fhir/StructureDefinition/'+id))
sdf-9: In any snapshot or differential, no label, code or requirements on the an element without a "." in the path (e.g. the first element) (: children().element.where(path.contains('.').not()).label.empty() and children().element.where(path.contains('.').not()).code.empty() and children().element.where(path.contains('.').not()).requirements.empty())
2. StructureDefinition.id
Definition

The logical id of the resource, as used in the URL for the resource. Once assigned, this value never changes.

Control0..1
Typeid
Comments

The only time that a resource does not have an id is when it is being submitted to the server using a create operation.

3. StructureDefinition.meta
Definition

The metadata about the resource. This is content that is maintained by the infrastructure. Changes to the content may not always be associated with version changes to the resource.

Control0..1
TypeMeta
4. StructureDefinition.implicitRules
Definition

A reference to a set of rules that were followed when the resource was constructed, and which must be understood when processing the content.

Control0..1
Typeuri
Is Modifiertrue
Comments

Asserting this rule set restricts the content to be only understood by a limited set of trading partners. This inherently limits the usefulness of the data in the long term. However, the existing health eco-system is highly fractured, and not yet ready to define, collect, and exchange data in a generally computable sense. Wherever possible, implementers and/or specification writers should avoid using this element.

This element is labelled as a modifier because the implicit rules may provide additional knowledge about the resource that modifies it's meaning or interpretation.

5. StructureDefinition.language
Definition

The base language in which the resource is written.

Control0..1
BindingThe codes SHALL be taken from Common Languages; other codes may be used where these codes are not suitable
Max Binding: All Languages A human language.

Typecode
Comments

Language is provided to support indexing and accessibility (typically, services such as text to speech use the language tag). The html language tag in the narrative applies to the narrative. The language tag on the resource may be used to specify the language of other presentations generated from the data in the resource Not all the content has to be in the base language. The Resource.language should not be assumed to apply to the narrative automatically. If a language is specified, it should it also be specified on the div element in the html (see rules in HTML5 for information about the relationship between xml:lang and the html lang attribute).

6. StructureDefinition.text
Definition

A human-readable narrative that contains a summary of the resource, and may be used to represent the content of the resource to a human. The narrative need not encode all the structured data, but is required to contain sufficient detail to make it "clinically safe" for a human to just read the narrative. Resource definitions may define what content should be represented in the narrative to ensure clinical safety.

Control0..1 This element is affected by the following invariants: dom-1
TypeNarrative
Alternate Namesnarrative, html, xhtml, display
Comments

Contained resources do not have narrative. Resources that are not contained SHOULD have a narrative. In some cases, a resource may only have text with little or no additional discrete data (as long as all minOccurs=1 elements are satisfied). This may be necessary for data from legacy systems where information is captured as a "text blob" or where text is additionally entered raw or narrated and encoded in formation is added later.

7. StructureDefinition.contained
Definition

These resources do not have an independent existence apart from the resource that contains them - they cannot be identified independently, and nor can they have their own independent transaction scope.

Control0..*
TypeResource
Alternate Namesinline resources, anonymous resources, contained resources
Comments

This should never be done when the content can be identified properly, as once identification is lost, it is extremely difficult (and context dependent) to restore it again.

8. StructureDefinition.extension
Definition

May be used to represent additional information that is not part of the basic definition of the resource. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

Control0..*
TypeExtension
Alternate Namesextensions, 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.

9. StructureDefinition.modifierExtension
Definition

May be used to represent additional information that is not part of the basic definition of the resource, and that modifies the understanding of the element that contains it. Usually modifier elements provide negation or qualification. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Control0..*
TypeExtension
Is Modifiertrue
Alternate Namesextensions, 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.

10. StructureDefinition.url
Definition

An absolute URI that is used to identify this structure definition when it is referenced in a specification, model, design or an instance. This SHALL be a URL, SHOULD be globally unique, and SHOULD be an address at which this structure definition is (or will be) published. The URL SHOULD include the major version of the structure definition. For more information see Technical and Business Versions.

Control1..1
Typeuri
Requirements

Allows the structure definition to be referenced by a single globally unique identifier.

Alternate Namesurl, authoritative-url, destination, identity
Comments

Can be a urn:uuid: or a urn:oid:, but real http: addresses are preferred. Multiple instances may share the same url if they have a distinct version.

11. StructureDefinition.identifier
Definition

A formal identifier that is used to identify this structure definition when it is represented in other formats, or referenced in a specification, model, design or an instance.

NoteThis is a business identifier, not a resource identifier (see discussion)
Control0..*
TypeIdentifier
Requirements

Allows externally provided and/or usable business identifiers to be easily associated with the module.

Comments

Typically, this is used for identifiers that can go in an HL7 V3 II (instance identifier) data type, e.g., to identify this structure definition outside of FHIR, where it is not possible to use the logical URI.

12. StructureDefinition.version
Definition

The identifier that is used to identify this version of the structure definition when it is referenced in a specification, model, design or instance. This is an arbitrary value managed by the structure definition author and is not expected to be globally unique. For example, it might be a timestamp (e.g. yyyymmdd) if a managed version is not available. There is also no expectation that versions can be placed in a lexicographical sequence.

NoteThis is a business versionId, not a resource version id (see discussion)
Control0..1
Typestring
Comments

There may be different structure definition instances that have the same identifier but different versions. The version can be appended to the url in a reference to allow a refrence to a particular business version of the structure definition with the format [url]|[version].

13. StructureDefinition.name
Definition

A natural language name identifying the structure definition. This name should be usable as an identifier for the module by machine processing applications such as code generation.

Control1..1
Typestring
Requirements

Support human navigation and code generation.

Comments

The name is not expected to be globally unique. The name should be a simple alpha-numeric type name to ensure that it is computable friendly.

14. StructureDefinition.title
Definition

A short, descriptive, user-friendly title for the structure definition.

Control0..1
Typestring
Comments

This name does not need to be machine-processing friendly and may contain punctuation, white-space, etc. Applications don't have to use this name, but can always fall back to it. The title also corresponds to the label for the root element.

15. StructureDefinition.status
Definition

The status of this structure definition. Enables tracking the life-cycle of the content.

Control1..1
BindingThe codes SHALL be taken from PublicationStatus The lifecycle status of a Value Set or Concept Map.

Typecode
Is Modifiertrue
Comments

Allows filtering of structure definitions that are appropriate for use vs. not.
This is labeled as "Is Modifier" because applications should not use a retired structure definition without due consideration.

16. StructureDefinition.experimental
Definition

A boolean value to indicate that this structure definition is authored for testing purposes (or education/evaluation/marketing), and is not intended to be used for genuine usage.

Control0..1
Typeboolean
Is Modifiertrue
Requirements

Enables experimental content to be developed following the same lifecycle that would be used for a production-level structure definition.

Comments

Allows filtering of structure definition that are appropriate for use vs. not. This is labeled as "Is Modifier" because applications should not use an experimental structure definition in production.

17. StructureDefinition.date
Definition

The date (and optionally time) when the structure definition was published. The date must change if and when the business version changes and it must change if the status code changes. In addition, it should change when the substantive content of the structure definition changes.

Control0..1
TypedateTime
Alternate NamesRevision Date
Comments

Note that this is not the same as the resource last-modified-date, since the resource may be a secondary representation of the structure definition. Additional specific dates may be added as extensions or be found by consulting Provenances associated with past versions of the resource.

18. StructureDefinition.publisher
Definition

The name of the individual or organization that published the structure definition.

Control0..1
Typestring
Requirements

Helps establish the "authority/credibility" of the structure definition. May also allow for contact.

Comments

Usually an organization, but may be an individual. The publisher (or steward) of the structure definition is the organization or individual primarily responsible for the maintenance and upkeep of the structure definition. This is not necessarily the same individual or organization that developed and initially authored the content. The publisher is the primary point of contact for questions or issues with the structure definition. This item SHOULD be populated unless the information is available from context.

19. StructureDefinition.contact
Definition

Contact details to assist a user in finding and communicating with the publisher.

Control0..*
TypeContactDetail
Comments

May be a web site, an email address, a telephone number, etc.

20. StructureDefinition.description
Definition

A free text natural language description of the structure definition from a consumer's perspective.

Control0..1
Typemarkdown
Comments

This description can be used to capture details such as why the structure definition was built, comments about misuse, instructions for clinical use and interpretation, literature references, examples from the paper world, etc. It is not a rendering of the structure definition as conveyed in the 'text' field of the resource itself. This item SHOULD be populated unless the information is available from context (e.g. the language of the profile is presumed to be the predominant language in the place the profile was created).

21. StructureDefinition.useContext
Definition

The content was developed with a focus and intent of supporting the contexts that are listed. These terms may be used to assist with indexing and searching for appropriate structure definition instances.

Control0..*
TypeUsageContext
Requirements

Assist in searching for appropriate content.

Comments

When multiple useContexts are specified, there is no expectation whether all or any of the contexts apply.

22. StructureDefinition.jurisdiction
Definition

A legal or geographic region in which the structure definition is intended to be used.

Control0..*
BindingThe codes SHALL be taken from Jurisdiction ValueSet; other codes may be used where these codes are not suitable Countries and regions within which this artifact is targeted for use

TypeCodeableConcept
Comments

It may be possible for the structure definition to be used in jurisdictions other than those for which it was originally designed or intended.

23. StructureDefinition.purpose
Definition

Explaination of why this structure definition is needed and why it has been designed as it has.

Control0..1
Typemarkdown
Comments

This element does not describe the usage of the structure definition Instead it provides traceability of ''why'' the resource is either needed or ''why'' it is defined as it is. This may be used to point to source materials or specifications that drove the structure of this structure definition.

24. StructureDefinition.copyright
Definition

A copyright statement relating to the structure definition and/or its contents. Copyright statements are generally legal restrictions on the use and publishing of the structure definition.

Control0..1
Typemarkdown
Requirements

Consumers must be able to determine any legal restrictions on the use of the structure definition and/or its content.

Alternate NamesLicense, Restrictions
25. StructureDefinition.keyword
Definition

A set of key words or terms from external terminologies that may be used to assist with indexing and searching of templates.

Control0..*
BindingFor example codes, see Structure Definition Codes Codes for the meaning of the defined structure (SNOMED CT and LOINC codes, as an example).

TypeCoding
Requirements

Assist in searching for appropriate StructureDefinitions.

26. StructureDefinition.fhirVersion
Definition

The version of the FHIR specification on which this StructureDefinition is based - this is the formal version of the specification, without the revision number, e.g. [publication].[major].[minor], which is 3.0.2 for this version.

Control0..1
Typeid
Comments

A StructureDefinition does not need to specify the target it applies to,as StructureDefinitions will often be valid across multiple versions of FHIR. FHIR tooling can determine whether a StructureDefinition is consistent with a particular StructureDefinition if desired.

27. StructureDefinition.mapping
Definition

An external specification that the content is mapped to.

Control0..*
TypeBackboneElement
InvariantsDefined on this element
ele-1: All FHIR elements must have a @value or children (: hasValue() | (children().count() > id.count()))
sdf-2: Must have at least a name or a uri (or both) (: name.exists() or uri.exists())
28. StructureDefinition.mapping.id
Definition

unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

Control0..1
Typestring
29. StructureDefinition.mapping.extension
Definition

May be used to represent additional information that is not part of the basic definition of the element. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

Control0..*
TypeExtension
Alternate Namesextensions, 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.

30. StructureDefinition.mapping.modifierExtension
Definition

May be used to represent additional information that is not part of the basic definition of the element, and that modifies the understanding of the element that contains it. Usually modifier elements provide negation or qualification. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Control0..*
TypeExtension
Is Modifiertrue
Alternate Namesextensions, user content, modifiers
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.

31. StructureDefinition.mapping.identity
Definition

An Internal id that is used to identify this mapping set when specific mappings are made.

Control1..1
Typeid
Comments

The specification is described once, with general comments, and then specific mappings are made that reference this declaration.

32. StructureDefinition.mapping.uri
Definition

An absolute URI that identifies the specification that this mapping is expressed to.

Control0..1 This element is affected by the following invariants: sdf-2
Typeuri
Comments

A formal identity for the specification being mapped to helps with identifying maps consistently.

33. StructureDefinition.mapping.name
Definition

A name for the specification that is being mapped to.

Control0..1 This element is affected by the following invariants: sdf-2
Typestring
34. StructureDefinition.mapping.comment
Definition

Comments about this mapping, including version notes, issues, scope limitations, and other important notes for usage.

Control0..1
Typestring
35. StructureDefinition.kind
Definition

Defines the kind of structure that this definition is describing.

Control1..1
BindingThe codes SHALL be taken from StructureDefinitionKind Defines the type of structure that a definition is describing.

Typecode
36. StructureDefinition.abstract
Definition

Whether structure this definition describes is abstract or not - that is, whether the structure is not intended to be instantiated. For Resources and Data types, abstract types will never be exchanged between systems.

Control1..1
Typeboolean
Comments

Abstract Resources cannot be instantiated - a concrete sub-type must be used. Abstract datatypes and extensions cannot be used in an instance. For logical models, the exact implication of "abstract" will rest with the author, depending how the logical model is used. Flagging a constraint structure as abstract conveys design intent but makes no difference to how the structure definition is handled. Note that inline declared elements that are given the type "Element" in the profile, but have children described, are anonymous concrete types that specialise Element.

37. StructureDefinition.contextType
Definition

If this is an extension, Identifies the context within FHIR resources where the extension can be used.

Control0..1 This element is affected by the following invariants: sdf-5
BindingThe codes SHALL be taken from ExtensionContext How an extension context is interpreted.

Typecode
38. StructureDefinition.context
Definition

Identifies the types of resource or data type elements to which the extension can be applied.

Control0..* This element is affected by the following invariants: sdf-5
Typestring
Comments

If the context is an element that can have multiple types, then use (e.g.) value[x] if the extension works on all choice types, or otherwise an enumeration of explicitly named elements if not. Note that a context of "string" doesn't mean that the extension can be used with one of the string patterns such as "id" etc.

39. StructureDefinition.contextInvariant
Definition

A set of rules as Fluent Invariants about when the extension can be used (e.g. co-occurrence variants for the extension).

Control0..* This element is affected by the following invariants: sdf-18
Typestring
Comments

All the rules must be true. When evaluating the invariant, the fluentpath focus is the element that holds the extension, and %extension refers to the extension itself.

40. StructureDefinition.type
Definition

The type this structure describes. If the derivation kind is 'specialization' then this is the master definition for a type, and there is always one of these (a data type, an extension, a resource, including abstract ones). Otherwise the structure definition is a constraint on the stated type (and in this case, the type cannot be an abstract type).

Control1..1 This element is affected by the following invariants: sdf-4, sdf-11
BindingThe codes SHALL be taken from FHIRDefinedType; other codes may be used where these codes are not suitable Either a resource or a data type, including logical model types

Typecode
Comments

Note that in the case of constraints, the type could be determined by chasing through the baseDefinition references until a concrete structure (derivation = specialization) is reached, or by looking at the path of the first element in the snapshot - if present - but providing the type directly makes for simpler tooling and indexing.

41. StructureDefinition.baseDefinition
Definition

An absolute URI that is the base structure from which this type is derived, either by specialization or constraint.

Control0..1 This element is affected by the following invariants: sdf-4
Typeuri
Comments

If differential constraints are specified in this structure, they are applied to the base in a "differential" fashion. If there is no base, then the differential constraints cannot be provided (snapshot only). Differential structures are useful for the editing perspective, and snapshot structures are suitable for operational use. The FHIR Project provides a number of tools/services to populate snapshots from differential constraints. Logical Models have a base of "Element" or another logical model.

42. StructureDefinition.derivation
Definition

How the type relates to the baseDefinition.

Control0..1
BindingThe codes SHALL be taken from TypeDerivationRule How a type relates to its baseDefinition.

Typecode
Comments

If the definition is a specialization, then it adds new elements in the differential, and the snapshot includes the inherited elements.

If the definition is a constraint, then it can not define new elements, it can only make new rules about existing content (see Profiling Resources).

43. StructureDefinition.snapshot
Definition

A snapshot view is expressed in a stand alone form that can be used and interpreted without considering the base StructureDefinition.

Control0..1 This element is affected by the following invariants: sdf-6
TypeBackboneElement
InvariantsDefined on this element
ele-1: All FHIR elements must have a @value or children (: hasValue() | (children().count() > id.count()))
sdf-15: The first element in a snapshot has no type (: kind!='logical' implies snapshot.element.first().type.empty())
sdf-3: Each element definition in a snapshot must have a formal definition and cardinalities (: element.all(definition and min and max))
sdf-8: In any snapshot, all the elements must be in the specified type (: (%resource.kind = 'logical' or element.first().path = %resource.type) and element.tail().all(path.startsWith(%resource.snapshot.element.first().path&'.')))
44. StructureDefinition.snapshot.id
Definition

unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

Control0..1
Typestring
45. StructureDefinition.snapshot.extension
Definition

May be used to represent additional information that is not part of the basic definition of the element. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

Control0..*
TypeExtension
Alternate Namesextensions, 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.

46. StructureDefinition.snapshot.modifierExtension
Definition

May be used to represent additional information that is not part of the basic definition of the element, and that modifies the understanding of the element that contains it. Usually modifier elements provide negation or qualification. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Control0..*
TypeExtension
Is Modifiertrue
Alternate Namesextensions, user content, modifiers
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.

47. StructureDefinition.snapshot.element
Definition

Captures constraints on each element within the resource.

Control1..* This element is affected by the following invariants: sdf-3
TypeElementDefinition
48. StructureDefinition.differential
Definition

A differential view is expressed relative to the base StructureDefinition - a statement of differences that it applies.

Control0..1 This element is affected by the following invariants: sdf-6
TypeBackboneElement
InvariantsDefined on this element
ele-1: All FHIR elements must have a @value or children (: hasValue() | (children().count() > id.count()))
sdf-15a: If the first element in a differential has no "." in the path, it has no type (: element.first().path.contains('.').not() implies element.first().type.empty())
sdf-20: No slicing on the root element (: element.where(path.contains('.').not()).slicing.empty())
sdf-8a: In any differential, all the elements must be in the specified type (: element.first().path.startsWith(%resource.type) and element.tail().all(path.startsWith(%resource.type&'.')))
49. StructureDefinition.differential.id
Definition

unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.

Control0..1
Typestring
50. StructureDefinition.differential.extension
Definition

May be used to represent additional information that is not part of the basic definition of the element. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

Control0..*
TypeExtension
Alternate Namesextensions, 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.

51. StructureDefinition.differential.modifierExtension
Definition

May be used to represent additional information that is not part of the basic definition of the element, and that modifies the understanding of the element that contains it. Usually modifier elements provide negation or qualification. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Control0..*
TypeExtension
Is Modifiertrue
Alternate Namesextensions, user content, modifiers
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.

52. StructureDefinition.differential.element
Definition

Captures constraints on each element within the resource.

Control1..*
TypeElementDefinition