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FHIR Infrastructure Work GroupMaturity Level: 5 Normative Compartments: Not linked to any defined compartments

Detailed Descriptions for the elements in the StructureDefinition resource.

StructureDefinition
Element IdStructureDefinition
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.

Control1..1
Alternate NamesTemplate; Profile
InvariantsDefined on this element
sdf-1: Element paths must be unique unless the structure is a constraint (expression : derivation = 'constraint' or snapshot.element.select(path).isDistinct(), xpath: (f:derivation/@value = 'constraint') or (count(f:snapshot/f:element) = count(distinct-values(f:snapshot/f:element/f:path/@value))))
sdf-11: If there's a type, its content must match the path name in the first element of a snapshot (expression : kind != 'logical' implies snapshot.empty() or snapshot.element.first().path = type, xpath: (f:kind/@value = 'logical') or not(exists(f:snapshot)) or (f:type/@value = f:snapshot/f:element[1]/f:path/@value))
sdf-12: element.base cannot appear if there is no base on the structure definition (expression : snapshot.exists() implies (snapshot.element.base.exists() = baseDefinition.exists()), xpath: f:baseDefinition or not(exists(f:snapshot/f:element/f:base) or exists(f:differential/f:element/f:base)))
sdf-14: All element definitions must have an id (expression : snapshot.element.all(id.exists()) and differential.element.all(id.exists()), xpath: count(*/f:element)=count(*/f:element/@id))
sdf-15: The first element in a snapshot has no type unless model is a logical model. (expression : kind!='logical' implies snapshot.element.first().type.empty(), xpath: f:kind/@value='logical' or not(f:snapshot/f:element[1]/f:type))
sdf-15a: If the first element in a differential has no "." in the path and it's not a logical model, it has no type (expression : (kind!='logical' and differential.element.first().path.contains('.').not()) implies differential.element.first().type.empty(), xpath: f:kind/@value='logical' or not(f:differential/f:element[1][not(contains(f:path/@value, '.'))]/f:type))
sdf-16: All element definitions must have unique ids (snapshot) (expression : snapshot.element.all(id) and snapshot.element.id.trace('ids').isDistinct(), xpath: count(f:snapshot/f:element)=count(f:snapshot/f:element/@id) and (count(f:snapshot/f:element)=count(distinct-values(f:snapshot/f:element/@id))))
sdf-17: All element definitions must have unique ids (diff) (expression : differential.element.all(id) and differential.element.id.trace('ids').isDistinct(), xpath: count(f:differential/f:element)=count(f:differential/f:element/@id) and (count(f:differential/f:element)=count(distinct-values(f:differential/f:element/@id))))
sdf-18: Context Invariants can only be used for extensions (expression : contextInvariant.exists() implies type = 'Extension', xpath: not(exists(f:contextInvariant)) or (f:type/@value = 'Extension'))
sdf-19: Custom types can only be used in logical models (expression : kind = 'logical' or (differential.element.type.code.all(hasValue() implies matches('^[a-zA-Z0-9]+$')) and snapshot.element.type.code.all(hasValue() implies matches('^[a-zA-Z0-9]+$'))), xpath: f:kind/@value = 'logical' or count(f:differential/f:element/f:type/f:code[@value and not(matches(string(@value), '^[a-zA-Z0-9]+$'))]|f:snapshot/f:element/f:type/f:code[@value and not(matches(string(@value), '^[a-zA-Z0-9]+$'))]) =0)
sdf-21: Default values can only be specified on logical models (expression : (snapshot.element.defaultValue.exists() or differential.element.defaultValue.exists()) implies ((kind = 'logical') and (derivation = 'specialization')), xpath: (not(exists(f:snapshot/f:element/*[starts-with(local-name(), 'defaultValue')])) and not(exists(f:differential/f:element/*[starts-with(local-name(), 'defaultValue')]))) or ((f:kind/@value = 'logical') and (f:derivation/@value = 'specialization')))
sdf-4: If the structure is not abstract, then there SHALL be a baseDefinition (expression : abstract = true or baseDefinition.exists(), xpath: (f:abstract/@value=true()) or exists(f:baseDefinition))
sdf-5: If the structure defines an extension then the structure must have context information (expression : type != 'Extension' or derivation = 'specialization' or (context.exists()), xpath: not(f:type/@value = 'extension') or (f:derivation/@value = 'specialization') or (exists(f:context)))
sdf-6: A structure must have either a differential, or a snapshot (or both) (expression : snapshot.exists() or differential.exists(), xpath: exists(f:snapshot) or exists(f:differential))
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 (expression : (derivation = 'constraint') or (kind = 'logical') or (url = 'http://hl7.org/fhir/StructureDefinition/'+id), xpath: (f:derivation/@value = 'constraint') or (f:kind/@value = 'logical') or (f:url/@value=concat('http://hl7.org/fhir/StructureDefinition/', f:id/@value)))
sdf-9: In any snapshot or differential, no label, code or requirements on an element without a "." in the path (e.g. the first element) (expression : 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(), xpath: not(exists(f:snapshot/f:element[not(contains(f:path/@value, '.')) and (f:label or f:code or f:requirements)])) and not(exists(f:differential/f:element[not(contains(f:path/@value, '.')) and (f:label or f:code or f:requirements)])))
StructureDefinition.url
Element IdStructureDefinition.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; also called its canonical identifier. This SHOULD be globally unique and SHOULD be a literal address at which this structure definition is (or will be) published.

Control1..1
Typeuri
Requirements

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

Alternate Namesurl; authoritative-url; destination; identity
Summarytrue
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.

The URL SHOULD include the major version of the structure definition. For more information see Technical and Business Versions.

StructureDefinition.identifier
Element IdStructureDefinition.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 identifer, not a resource identifier (see discussion)
Control0..*
TypeIdentifier
Requirements

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

Summarytrue
Comments

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

StructureDefinition.version
Element IdStructureDefinition.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
Summarytrue
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 reference to a particular business version of the structure definition with the format [url]|[version].

StructureDefinition.name
Element IdStructureDefinition.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.

Summarytrue
Comments

The name is not expected to be globally unique. The name should be a simple alphanumeric type name to ensure that it is machine-processing friendly.

StructureDefinition.title
Element IdStructureDefinition.title
Definition

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

Control0..1
Typestring
Summarytrue
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.

StructureDefinition.status
Element IdStructureDefinition.status
Definition

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

Control1..1
Terminology BindingPublicationStatus (Required)
Typecode
Is Modifiertrue (Reason: null)
Summarytrue
Comments

Allows filtering of structure definitions that are appropriate for use versus not.

StructureDefinition.experimental
Element IdStructureDefinition.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 (Reason: null)
Requirements

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

Summarytrue
Comments

Allows filtering of structure definitions that are appropriate for use versus not.

StructureDefinition.date
Element IdStructureDefinition.date
Definition

The date (and optionally time) when the structure definition was published. The date must change 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
Summarytrue
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.

StructureDefinition.publisher
Element IdStructureDefinition.publisher
Definition

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

Control0..1
Typestring
Requirements

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

Summarytrue
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.

StructureDefinition.contact
Element IdStructureDefinition.contact
Definition

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

Control0..*
TypeContactDetail
Summarytrue
Comments

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

StructureDefinition.description
Element IdStructureDefinition.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).

StructureDefinition.useContext
Standards StatusThis element has a standards status of "Trial Use" which is different to the status of the whole resource
Element IdStructureDefinition.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.

Summarytrue
Comments

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

StructureDefinition.jurisdiction
Element IdStructureDefinition.jurisdiction
Definition

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

Control0..*
Terminology BindingJurisdiction ValueSet (Extensible)
TypeCodeableConcept
Summarytrue
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.

StructureDefinition.purpose
Element IdStructureDefinition.purpose
Definition

Explanation 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.

StructureDefinition.copyright
Element IdStructureDefinition.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
StructureDefinition.keyword
Element IdStructureDefinition.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..*
Terminology BindingStructure Definition Codes (Example)
TypeCoding
Requirements

Assist in searching for appropriate StructureDefinitions.

Summarytrue
StructureDefinition.fhirVersion
Element IdStructureDefinition.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 3.4.0 for this version.

Control0..1
Terminology BindingAll Published FHIR versions (Required)
Typeid
Summarytrue
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.

StructureDefinition.mapping
Element IdStructureDefinition.mapping
Definition

An external specification that the content is mapped to.

Control0..*
InvariantsDefined on this element
sdf-2: Must have at least a name or a uri (or both) (expression : name.exists() or uri.exists(), xpath: exists(f:uri) or exists(f:name))
StructureDefinition.mapping.identity
Element IdStructureDefinition.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.

StructureDefinition.mapping.uri
Element IdStructureDefinition.mapping.uri
Definition

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

Control0..1
Typeuri
Comments

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

InvariantsAffect this element
sdf-2: Must have at least a name or a uri (or both) (expression : name.exists() or uri.exists(), xpath: exists(f:uri) or exists(f:name))
StructureDefinition.mapping.name
Element IdStructureDefinition.mapping.name
Definition

A name for the specification that is being mapped to.

Control0..1
Typestring
InvariantsAffect this element
sdf-2: Must have at least a name or a uri (or both) (expression : name.exists() or uri.exists(), xpath: exists(f:uri) or exists(f:name))
StructureDefinition.mapping.comment
Element IdStructureDefinition.mapping.comment
Definition

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

Control0..1
Typestring
StructureDefinition.kind
Element IdStructureDefinition.kind
Definition

Defines the kind of structure that this definition is describing.

Control1..1
Terminology BindingStructureDefinitionKind (Required)
Typecode
Summarytrue
StructureDefinition.abstract
Element IdStructureDefinition.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
Summarytrue
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 specialize Element.

StructureDefinition.context
Element IdStructureDefinition.context
Definition

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

Control0..*
Summarytrue
InvariantsAffect this element
sdf-5: If the structure defines an extension then the structure must have context information (expression : type != 'Extension' or derivation = 'specialization' or (context.exists()), xpath: not(f:type/@value = 'extension') or (f:derivation/@value = 'specialization') or (exists(f:context)))
StructureDefinition.context.type
Element IdStructureDefinition.context.type
Definition

Defines how to interpret the expression that defines what the context of the extension is.

Control1..1
Terminology BindingExtensionContextType (Required)
Typecode
Summarytrue
StructureDefinition.context.expression
Element IdStructureDefinition.context.expression
Definition

An expression that defines where an extension can be used in resources.

Control1..1
Typestring
Summarytrue
StructureDefinition.contextInvariant
Element IdStructureDefinition.contextInvariant
Definition

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

Control0..*
Typestring
Summarytrue
Comments

The rules are only evaluated when the extension is present. When evaluating the invariant, the FHIRPath focus is the element that holds the extension, and %extension refers to the extension itself.

InvariantsAffect this element
sdf-18: Context Invariants can only be used for extensions (expression : contextInvariant.exists() implies type = 'Extension', xpath: not(exists(f:contextInvariant)) or (f:type/@value = 'Extension'))
StructureDefinition.type
Element IdStructureDefinition.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). References are URLs that are relative to http://hl7.org/fhir/StructureDefinition e.g. "string" is a reference to http://hl7.org/fhir/StructureDefinition/string. Absolute URLs are only allowed in logical models.

Control1..1
Terminology BindingFHIRDefinedType (Extensible)
Typeuri
Summarytrue
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.

The type must match the elements defined in the differential and the snapshot. For all FHIR defined types, the path name of the element will start with the type name. For logical models, where the type is a URL, the type name SHOULD start with the tail of the type URL where required.

InvariantsAffect this element
sdf-11: If there's a type, its content must match the path name in the first element of a snapshot (expression : kind != 'logical' implies snapshot.empty() or snapshot.element.first().path = type, xpath: (f:kind/@value = 'logical') or not(exists(f:snapshot)) or (f:type/@value = f:snapshot/f:element[1]/f:path/@value))
StructureDefinition.baseDefinition
Element IdStructureDefinition.baseDefinition
Definition

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

Control0..1
Typecanonical(StructureDefinition)
HierarchyThis reference is part of a strict Hierarchy
Summarytrue
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.

InvariantsAffect this element
sdf-4: If the structure is not abstract, then there SHALL be a baseDefinition (expression : abstract = true or baseDefinition.exists(), xpath: (f:abstract/@value=true()) or exists(f:baseDefinition))
StructureDefinition.derivation
Element IdStructureDefinition.derivation
Definition

How the type relates to the baseDefinition.

Control0..1
Terminology BindingTypeDerivationRule (Required)
Typecode
Summarytrue
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 cannot define new elements, it can only make new rules about existing content (see Profiling Resources).

StructureDefinition.snapshot
Element IdStructureDefinition.snapshot
Definition

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

Control0..1
InvariantsDefined on this element
sdf-3: Each element definition in a snapshot must have a formal definition and cardinalities (expression : element.all(definition.exists() and min.exists() and max.exists()), xpath: count(f:element) = count(f:element[exists(f:definition) and exists(f:min) and exists(f:max)]))
sdf-8: All snapshot elements must be in the StructureDefinition's specified type (expression : element.first().path = %resource.type and element.tail().all(path.startsWith(%resource.type&'.')), xpath: f:element[1]/f:path/@value=parent::f:StructureDefinition/f:type/@value and count(f:element[position()!=1])=count(f:element[position()!=1][starts-with(f:path/@value, concat(ancestor::f:StructureDefinition/f:type/@value, '.'))]))
sdf-8b: All snapshot elements must have a base definition (expression : element.all(base.exists()), xpath: count(f:element) = count(f:element/f:base))
Affect this element
sdf-6: A structure must have either a differential, or a snapshot (or both) (expression : snapshot.exists() or differential.exists(), xpath: exists(f:snapshot) or exists(f:differential))
StructureDefinition.snapshot.element
Element IdStructureDefinition.snapshot.element
Definition

Captures constraints on each element within the resource.

Control1..*
TypeElementDefinition
InvariantsDefined on this element
sdf-10: provide either a binding reference or a description (or both) (expression : binding.empty() or binding.valueSet.exists() or binding.description.exists(), xpath: not(exists(f:binding)) or exists(f:binding/f:valueSet) or exists(f:binding/f:description))
Affect this element
sdf-3: Each element definition in a snapshot must have a formal definition and cardinalities (expression : element.all(definition.exists() and min.exists() and max.exists()), xpath: count(f:element) = count(f:element[exists(f:definition) and exists(f:min) and exists(f:max)]))
StructureDefinition.differential
Element IdStructureDefinition.differential
Definition

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

Control0..1
InvariantsDefined on this element
sdf-20: No slicing on the root element (expression : element.where(path.contains('.').not()).slicing.empty(), xpath: not(f:element[1]/f:slicing))
sdf-8a: In any differential, all the elements must be in the specified type (expression : element.first().path.startsWith(%resource.type) and (element.tail().not() or element.tail().all(path.startsWith(%resource.type&'.'))), xpath: count(f:element)=count(f:element[f:path/@value=ancestor::f:StructureDefinition/f:type/@value or starts-with(f:path/@value, concat(ancestor::f:StructureDefinition/f:type/@value, '.'))]))
Affect this element
sdf-6: A structure must have either a differential, or a snapshot (or both) (expression : snapshot.exists() or differential.exists(), xpath: exists(f:snapshot) or exists(f:differential))
StructureDefinition.differential.element
Element IdStructureDefinition.differential.element
Definition

Captures constraints on each element within the resource.

Control1..*
TypeElementDefinition