Release 5

This page is part of the FHIR Specification (v5.0.0: R5 - STU). This is the current published version. For a full list of available versions, see the Directory of published versions . Page versions: R5 R4B R4 R3 R2

FHIR Infrastructure icon Work GroupMaturity Level: N Normative (from v4.0.0)Security Category: Anonymous Compartments: No 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.

Short DisplayStructural Definition
Cardinality0..*
TypeCanonicalResource
Alternate NamesTemplate; Profile
Summaryfalse
Invariants
Defined on this element
cnl-0Warning Name should be usable as an identifier for the module by machine processing applications such as code generationname.exists() implies name.matches('^[A-Z]([A-Za-z0-9_]){1,254}$')
sdf-1Rule Element paths must be unique unless the structure is a constraintderivation = 'constraint' or snapshot.element.select(path).isDistinct()
sdf-4Rule If the structure is not abstract, then there SHALL be a baseDefinitionabstract = true or baseDefinition.exists()
sdf-5Rule If the structure defines an extension then the structure must have context informationtype != 'Extension' or derivation = 'specialization' or (context.exists())
sdf-6Rule A structure must have either a differential, or a snapshot (or both)snapshot.exists() or differential.exists()
sdf-11Rule If there's a type, its content must match the path name in the first element of a snapshotkind != 'logical' implies snapshot.empty() or snapshot.element.first().path = type
sdf-14Rule All element definitions must have an idsnapshot.element.all(id.exists()) and differential.element.all(id.exists())
sdf-15Rule The first element in a snapshot has no type unless model is a logical model.kind!='logical' implies snapshot.element.first().type.empty()
sdf-15aRule If the first element in a differential has no "." in the path and it's not a logical model, it has no type(kind!='logical' and differential.element.first().path.contains('.').not()) implies differential.element.first().type.empty()
sdf-9Rule In any snapshot or differential, no label, code or requirements on 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()
sdf-16Rule All element definitions must have unique ids (snapshot)snapshot.element.all(id.exists()) and snapshot.element.id.trace('ids').isDistinct()
sdf-17Rule All element definitions must have unique ids (diff)differential.element.all(id.exists()) and differential.element.id.trace('ids').isDistinct()
sdf-18Rule Context Invariants can only be used for extensionscontextInvariant.exists() implies type = 'Extension'
sdf-19Rule FHIR Specification models only use FHIR defined typesurl.startsWith('http://hl7.org/fhir/StructureDefinition') implies (differential | snapshot).element.type.code.all(matches('^[a-zA-Z0-9]+$') or matches('^http:\\/\\/hl7\\.org\\/fhirpath\\/System\\.[A-Z][A-Za-z]+$'))
sdf-21Rule Default values can only be specified on specializationsdifferential.element.defaultValue.exists() implies (derivation = 'specialization')
sdf-22Rule FHIR Specification models never have default valuesurl.startsWith('http://hl7.org/fhir/StructureDefinition') implies (snapshot.element.defaultValue.empty() and differential.element.defaultValue.empty())
sdf-23Rule No slice name on root(snapshot | differential).element.all(path.contains('.').not() implies sliceName.empty())
sdf-27Rule If there's a base definition, there must be a derivation baseDefinition.exists() implies derivation.exists()
sdf-29Warning Elements in Resources must have a min cardinality or 0 or 1 and a max cardinality of 1 or *((kind in 'resource' | 'complex-type') and (derivation = 'specialization')) implies differential.element.where((min != 0 and min != 1) or (max != '1' and max != '*')).empty()
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 an authoritative instance of this structure definition is (or will be) published. This URL can be the target of a canonical reference. It SHALL remain the same when the structure definition is stored on different servers.

Short DisplayCanonical identifier for this structure definition, represented as a URI (globally unique)
Cardinality1..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 determination of when to create a new version of a resource (same url, new version) vs. defining a new artifact is up to the author. Considerations for making this decision are found in Technical and Business Versions.

In some cases, the resource can no longer be found at the stated url, but the url itself cannot change. Implementations can use the meta.source element to indicate where the current master source of the resource can be found.

Invariants
Defined on this element
cnl-1Warning URL should not contain | or # - these characters make processing canonical references problematicexists() implies matches('^[^|# ]+$')
Affect this element
sdf-19Rule FHIR Specification models only use FHIR defined typesurl.startsWith('http://hl7.org/fhir/StructureDefinition') implies (differential | snapshot).element.type.code.all(matches('^[a-zA-Z0-9]+$') or matches('^http:\\/\\/hl7\\.org\\/fhirpath\\/System\\.[A-Z][A-Za-z]+$'))
sdf-22Rule FHIR Specification models never have default valuesurl.startsWith('http://hl7.org/fhir/StructureDefinition') implies (snapshot.element.defaultValue.empty() and differential.element.defaultValue.empty())
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.

Short DisplayAdditional identifier for the structure definition
NoteThis is a business identifier, not a resource identifier (see discussion)
Cardinality0..*
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. There is no expectation that versions can be placed in a lexicographical sequence, so authors are encouraged to populate the StructureDefinition.versionAlgorithm[x] element to enable comparisons. If there is no managed version available, authors can consider using ISO date/time syntax (e.g., '2023-01-01').

Short DisplayBusiness version of the structure definition
NoteThis is a business versionId, not a resource version id (see discussion)
Cardinality0..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]. The version SHOULD NOT contain a '#' - see Business Version.

StructureDefinition.versionAlgorithm[x]
Element IdStructureDefinition.versionAlgorithm[x]
Definition

Indicates the mechanism used to compare versions to determine which is more current.

Short DisplayHow to compare versions
Cardinality0..1
Terminology BindingVersion Algorithm (Extensible)
Typestring|Coding
[x] NoteSee Choice of Datatypes for further information about how to use [x]
Summarytrue
Comments

If set as a string, this is a FHIRPath expression that has two additional context variables passed in - %version1 and %version2 and will return a negative number if version1 is newer, a positive number if version2 and a 0 if the version ordering can't be successfully be determined.

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.

Short DisplayName for this structure definition (computer friendly)
Cardinality1..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.Some Examples:

  • O2SatObservation
  • PresentationReport
  • Immunization2
  • AcmeAdmissionRecordOld.
Invariants
Affect this element
cnl-0Warning Name should be usable as an identifier for the module by machine processing applications such as code generationname.exists() implies name.matches('^[A-Z]([A-Za-z0-9_]){1,254}$')
StructureDefinition.title
Element IdStructureDefinition.title
Definition

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

Short DisplayName for this structure definition (human friendly)
Cardinality0..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.

Short Displaydraft | active | retired | unknown
Cardinality1..1
Terminology BindingPublicationStatus (Required)
Typecode
Is Modifiertrue (Reason: This is labeled as "Is Modifier" because applications should not use a retired {{title}} without due consideration)
Summarytrue
Comments

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

See guidance around (not) making local changes to elements here.

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.

Short DisplayFor testing purposes, not real usage
Cardinality0..1
Typeboolean
Meaning if MissingIf absent, this resource is treated as though it is not experimental.
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 last significantly changed. 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.

Short DisplayDate last changed
Cardinality0..1
TypedateTime
Alternate NamesRevision Date
Summarytrue
Comments

The date is often not tracked until the resource is published, but may be present on draft content. 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.

See guidance around (not) making local changes to elements here.

StructureDefinition.publisher
Element IdStructureDefinition.publisher
Definition

The name of the organization or individual responsible for the release and ongoing maintenance of the structure definition.

Short DisplayName of the publisher/steward (organization or individual)
Cardinality0..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.

Short DisplayContact details for the publisher
Cardinality0..*
TypeContactDetail
Summarytrue
Comments

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

See guidance around (not) making local changes to elements here.

StructureDefinition.description
Element IdStructureDefinition.description
Definition

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

Short DisplayNatural language description of the structure definition
Cardinality0..1
Typemarkdown
Summaryfalse
Comments

This description can be used to capture details such as 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 structure definition is presumed to be the predominant language in the place the structure definition was created).

StructureDefinition.useContext
Element IdStructureDefinition.useContext
Definition

The content was developed with a focus and intent of supporting the contexts that are listed. These contexts may be general categories (gender, age, ...) or may be references to specific programs (insurance plans, studies, ...) and may be used to assist with indexing and searching for appropriate structure definition instances.

Short DisplayThe context that the content is intended to support
Cardinality0..*
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
Standards StatusThis element has a standards status of "Deprecated" which is different from the status of the whole resource
Element IdStructureDefinition.jurisdiction
Definition

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

Short DisplayIntended jurisdiction for structure definition (if applicable)
Cardinality0..*
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.

DEPRECATION NOTE: For consistency, implementations are encouraged to migrate to using the new 'jurisdiction' code in the useContext element. (I.e. useContext.code indicating http://terminology.hl7.org/CodeSystem/usage-context-type#jurisdiction and useContext.valueCodeableConcept indicating the jurisdiction.)

StructureDefinition.purpose
Element IdStructureDefinition.purpose
Definition

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

Short DisplayWhy this structure definition is defined
Cardinality0..1
Typemarkdown
Summaryfalse
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. The short copyright declaration (e.g. (c) '2015+ xyz organization' should be sent in the copyrightLabel element.

Short DisplayUse and/or publishing restrictions
Cardinality0..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
Summaryfalse
Comments

...

StructureDefinition.copyrightLabel
Element IdStructureDefinition.copyrightLabel
Definition

A short string (<50 characters), suitable for inclusion in a page footer that identifies the copyright holder, effective period, and optionally whether rights are resctricted. (e.g. 'All rights reserved', 'Some rights reserved').

Short DisplayCopyright holder and year(s)
Cardinality0..1
Typestring
Requirements

Defines the content expected to be rendered in all representations of the artifact.

Summaryfalse
Comments

The (c) symbol should NOT be included in this string. It will be added by software when rendering the notation. Full details about licensing, restrictions, warrantees, etc. goes in the more general 'copyright' element.

StructureDefinition.keyword
Standards StatusThis element has a standards status of "Deprecated" which is different from the status of the whole resource

Use the artifact-topic extension instead

Element IdStructureDefinition.keyword
Definition

(DEPRECATED) A set of key words or terms from external terminologies that may be used to assist with indexing and searching of templates nby describing the use of this structure definition, or the content it describes.

Short DisplayAssist with indexing and finding
Cardinality0..*
Terminology BindingStructure Definition Use Codes / Keywords (Extensible)
TypeCoding
Requirements

Assist in searching for appropriate StructureDefinitions.

Summarytrue
Comments

Note that this element is deprecated. Use the http://hl7.org/fhir/StructureDefinition/artifact-topic extension instead.

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 4.6.0. for this version.

Short DisplayFHIR Version this StructureDefinition targets
Cardinality0..1
Terminology BindingFHIRVersion (Required)
Typecode
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.

Short DisplayExternal specification that the content is mapped to
Cardinality0..*
Summaryfalse
Invariants
Defined on this element
sdf-2Rule Must have at least a name or a uri (or both)name.exists() or uri.exists()
StructureDefinition.mapping.identity
Element IdStructureDefinition.mapping.identity
Definition

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

Short DisplayInternal id when this mapping is used
Cardinality1..1
Typeid
Summaryfalse
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.

Short DisplayIdentifies what this mapping refers to
Cardinality0..1
Typeuri
Summaryfalse
Comments

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

Invariants
Affect this element
sdf-2Rule Must have at least a name or a uri (or both)name.exists() or uri.exists()
StructureDefinition.mapping.name
Element IdStructureDefinition.mapping.name
Definition

A name for the specification that is being mapped to.

Short DisplayNames what this mapping refers to
Cardinality0..1
Typestring
Summaryfalse
Invariants
Affect this element
sdf-2Rule Must have at least a name or a uri (or both)name.exists() or uri.exists()
StructureDefinition.mapping.comment
Element IdStructureDefinition.mapping.comment
Definition

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

Short DisplayVersions, Issues, Scope limitations etc
Cardinality0..1
Typestring
Summaryfalse
StructureDefinition.kind
Element IdStructureDefinition.kind
Definition

Defines the kind of structure that this definition is describing.

Short Displayprimitive-type | complex-type | resource | logical
Cardinality1..1
Terminology BindingStructure Definition Kind (Required)
Typecode
Summarytrue
Invariants
Affect this element
sdf-15aRule If the first element in a differential has no "." in the path and it's not a logical model, it has no type(kind!='logical' and differential.element.first().path.contains('.').not()) implies differential.element.first().type.empty()
sdf-15Rule The first element in a snapshot has no type unless model is a logical model.kind!='logical' implies snapshot.element.first().type.empty()
sdf-11Rule If there's a type, its content must match the path name in the first element of a snapshotkind != 'logical' implies snapshot.empty() or snapshot.element.first().path = type
sdf-29Warning Elements in Resources must have a min cardinality or 0 or 1 and a max cardinality of 1 or *((kind in 'resource' | 'complex-type') and (derivation = 'specialization')) implies differential.element.where((min != 0 and min != 1) or (max != '1' and max != '*')).empty()
sdf-8Rule All snapshot elements must start with the StructureDefinition's specified type for non-logical models, or with the same type name for logical models(%resource.kind = 'logical' or element.first().path = %resource.type) and element.tail().all(path.startsWith(%resource.snapshot.element.first().path&'.'))
sdf-3Rule Each element definition in a snapshot must have a formal definition and cardinalities, unless model is a logical model%resource.kind = 'logical' or element.all(definition.exists() and min.exists() and max.exists())
sdf-8aRule In any differential, all the elements must start with the StructureDefinition's specified type for non-logical models, or with the same type name for logical models(%resource.kind = 'logical' or element.first().path.startsWith(%resource.type)) and (element.tail().empty() or element.tail().all(path.startsWith(%resource.differential.element.first().path.replaceMatches('\\..*','')&'.')))
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.

Short DisplayWhether the structure is abstract
Cardinality1..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 StructureDefinition, but have children described, are anonymous concrete types that specialize Element.

Invariants
Affect this element
sdf-4Rule If the structure is not abstract, then there SHALL be a baseDefinitionabstract = true or baseDefinition.exists()
StructureDefinition.context
Element IdStructureDefinition.context
Definition

Identifies the types of resource or data type elements to which the extension can be applied. For more guidance on using the 'context' element, see the defining extensions page.

Short DisplayIf an extension, where it can be used in instances
Cardinality0..*
Summarytrue
Invariants
Affect this element
sdf-5Rule If the structure defines an extension then the structure must have context informationtype != 'Extension' or derivation = 'specialization' or (context.exists())
StructureDefinition.context.type
Element IdStructureDefinition.context.type
Definition

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

Short Displayfhirpath | element | extension
Cardinality1..1
Terminology BindingExtension Context Type (Required)
Typecode
Summarytrue
StructureDefinition.context.expression
Element IdStructureDefinition.context.expression
Definition

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

Short DisplayWhere the extension can be used in instances
Cardinality1..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.

Short DisplayFHIRPath invariants - when the extension can be used
Cardinality0..*
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.

Invariants
Affect this element
sdf-18Rule Context Invariants can only be used for extensionscontextInvariant.exists() implies type = '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, where they are required.

Short DisplayType defined or constrained by this structure
Cardinality1..1
Terminology BindingAll FHIR Types (Extensible)
Typeuri
Summarytrue
Comments

Note that in the case of constraints, the type could be determined by chasing through the baseDefinition references until a type defining 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 SHALL be a fully specified URL, the type name SHOULD start with the final path segment of the type URL where required. E.g. If the type was "http://example.org/fhir/MyLogicalModelType", the type name should start with 'MyLogicalModelType'.

Invariants
Affect this element
sdf-18Rule Context Invariants can only be used for extensionscontextInvariant.exists() implies type = 'Extension'
sdf-11Rule If there's a type, its content must match the path name in the first element of a snapshotkind != 'logical' implies snapshot.empty() or snapshot.element.first().path = type
sdf-5Rule If the structure defines an extension then the structure must have context informationtype != 'Extension' or derivation = 'specialization' or (context.exists())
sdf-8Rule All snapshot elements must start with the StructureDefinition's specified type for non-logical models, or with the same type name for logical models(%resource.kind = 'logical' or element.first().path = %resource.type) and element.tail().all(path.startsWith(%resource.snapshot.element.first().path&'.'))
sdf-8aRule In any differential, all the elements must start with the StructureDefinition's specified type for non-logical models, or with the same type name for logical models(%resource.kind = 'logical' or element.first().path.startsWith(%resource.type)) and (element.tail().empty() or element.tail().all(path.startsWith(%resource.differential.element.first().path.replaceMatches('\\..*','')&'.')))
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.

Short DisplayDefinition that this type is constrained/specialized from
Cardinality0..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 "Base", "Element" or another logical model.

Invariants
Affect this element
sdf-4Rule If the structure is not abstract, then there SHALL be a baseDefinitionabstract = true or baseDefinition.exists()
sdf-27Rule If there's a base definition, there must be a derivation baseDefinition.exists() implies derivation.exists()
StructureDefinition.derivation
Element IdStructureDefinition.derivation
Definition

How the type relates to the baseDefinition.

Short Displayspecialization | constraint - How relates to base definition
Cardinality0..1
Terminology BindingType Derivation Rule (Required)
Typecode
Summarytrue
Comments

If the definition is a specialization, then it adds to the differential new elements and optionally additional rules to an existing concrete type, and the snapshot includes the inherited elements and rules. If the definition is a constraint, then it cannot define new elements, it can only make new rules about existing content (see Profiling Resources).

Invariants
Affect this element
sdf-1Rule Element paths must be unique unless the structure is a constraintderivation = 'constraint' or snapshot.element.select(path).isDistinct()
sdf-21Rule Default values can only be specified on specializationsdifferential.element.defaultValue.exists() implies (derivation = 'specialization')
sdf-5Rule If the structure defines an extension then the structure must have context informationtype != 'Extension' or derivation = 'specialization' or (context.exists())
sdf-27Rule If there's a base definition, there must be a derivation baseDefinition.exists() implies derivation.exists()
sdf-29Warning Elements in Resources must have a min cardinality or 0 or 1 and a max cardinality of 1 or *((kind in 'resource' | 'complex-type') and (derivation = 'specialization')) implies differential.element.where((min != 0 and min != 1) or (max != '1' and max != '*')).empty()
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.

Short DisplaySnapshot view of the structure
Cardinality0..1
Summaryfalse
Invariants
Defined on this element
sdf-3Rule Each element definition in a snapshot must have a formal definition and cardinalities, unless model is a logical model%resource.kind = 'logical' or element.all(definition.exists() and min.exists() and max.exists())
sdf-8Rule All snapshot elements must start with the StructureDefinition's specified type for non-logical models, or with the same type name for logical models(%resource.kind = 'logical' or element.first().path = %resource.type) and element.tail().all(path.startsWith(%resource.snapshot.element.first().path&'.'))
sdf-24Rule For CodeableReference elements, target profiles must be listed on the CodeableReference, not the CodeableReference.referenceelement.where(type.where(code='Reference').exists() and path.endsWith('.reference') and type.targetProfile.exists() and (path.substring(0,$this.path.length()-10) in %context.element.where(type.where(code='CodeableReference').exists()).path)).exists().not()
sdf-25Rule For CodeableReference elements, bindings must be listed on the CodeableReference, not the CodeableReference.conceptelement.where(type.where(code='CodeableConcept').exists() and path.endsWith('.concept') and binding.exists() and (path.substring(0,$this.path.length()-8) in %context.element.where(type.where(code='CodeableReference').exists()).path)).exists().not()
sdf-26Guideline The root element of a profile should not have mustSupport = true$this.where(element[0].mustSupport='true').exists().not()
This is (only) a best practice guideline because:

It is bad practice to set the root element of a profile to 'mustSupport' as mustSupport should always be determined by the element referencing a type. The designer of a StructureDefinition cannot know all circumstances in which a type or profile might be used

sdf-8bRule All snapshot elements must have a base definitionelement.all(base.exists())
Affect this element
sdf-11Rule If there's a type, its content must match the path name in the first element of a snapshotkind != 'logical' implies snapshot.empty() or snapshot.element.first().path = type
sdf-1Rule Element paths must be unique unless the structure is a constraintderivation = 'constraint' or snapshot.element.select(path).isDistinct()
sdf-6Rule A structure must have either a differential, or a snapshot (or both)snapshot.exists() or differential.exists()
StructureDefinition.snapshot.element
Element IdStructureDefinition.snapshot.element
Definition

Captures constraints on each element within the resource.

Short DisplayDefinition of elements in the resource (if no StructureDefinition)
Cardinality1..*
TypeElementDefinition
Summaryfalse
Invariants
Defined on this element
sdf-10Rule provide either a binding reference or a description (or both)binding.empty() or binding.valueSet.exists() or binding.description.exists()
sdf-28Rule If there are no discriminators, there must be a definitionslicing.exists().not() or (slicing.discriminator.exists() or slicing.description.exists())
Affect this element
sdf-9Rule In any snapshot or differential, no label, code or requirements on 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()
sdf-19Rule FHIR Specification models only use FHIR defined typesurl.startsWith('http://hl7.org/fhir/StructureDefinition') implies (differential | snapshot).element.type.code.all(matches('^[a-zA-Z0-9]+$') or matches('^http:\\/\\/hl7\\.org\\/fhirpath\\/System\\.[A-Z][A-Za-z]+$'))
sdf-16Rule All element definitions must have unique ids (snapshot)snapshot.element.all(id.exists()) and snapshot.element.id.trace('ids').isDistinct()
sdf-15Rule The first element in a snapshot has no type unless model is a logical model.kind!='logical' implies snapshot.element.first().type.empty()
sdf-23Rule No slice name on root(snapshot | differential).element.all(path.contains('.').not() implies sliceName.empty())
sdf-11Rule If there's a type, its content must match the path name in the first element of a snapshotkind != 'logical' implies snapshot.empty() or snapshot.element.first().path = type
sdf-22Rule FHIR Specification models never have default valuesurl.startsWith('http://hl7.org/fhir/StructureDefinition') implies (snapshot.element.defaultValue.empty() and differential.element.defaultValue.empty())
sdf-14Rule All element definitions must have an idsnapshot.element.all(id.exists()) and differential.element.all(id.exists())
sdf-1Rule Element paths must be unique unless the structure is a constraintderivation = 'constraint' or snapshot.element.select(path).isDistinct()
sdf-8Rule All snapshot elements must start with the StructureDefinition's specified type for non-logical models, or with the same type name for logical models(%resource.kind = 'logical' or element.first().path = %resource.type) and element.tail().all(path.startsWith(%resource.snapshot.element.first().path&'.'))
sdf-3Rule Each element definition in a snapshot must have a formal definition and cardinalities, unless model is a logical model%resource.kind = 'logical' or element.all(definition.exists() and min.exists() and max.exists())
sdf-8bRule All snapshot elements must have a base definitionelement.all(base.exists())
sdf-24Rule For CodeableReference elements, target profiles must be listed on the CodeableReference, not the CodeableReference.referenceelement.where(type.where(code='Reference').exists() and path.endsWith('.reference') and type.targetProfile.exists() and (path.substring(0,$this.path.length()-10) in %context.element.where(type.where(code='CodeableReference').exists()).path)).exists().not()
sdf-25Rule For CodeableReference elements, bindings must be listed on the CodeableReference, not the CodeableReference.conceptelement.where(type.where(code='CodeableConcept').exists() and path.endsWith('.concept') and binding.exists() and (path.substring(0,$this.path.length()-8) in %context.element.where(type.where(code='CodeableReference').exists()).path)).exists().not()
sdf-26Guideline The root element of a profile should not have mustSupport = true$this.where(element[0].mustSupport='true').exists().not()
This is (only) a best practice guideline because:

It is bad practice to set the root element of a profile to 'mustSupport' as mustSupport should always be determined by the element referencing a type. The designer of a StructureDefinition cannot know all circumstances in which a type or profile might be used

StructureDefinition.differential
Element IdStructureDefinition.differential
Definition

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

Short DisplayDifferential view of the structure
Cardinality0..1
Summaryfalse
Invariants
Defined on this element
sdf-20Rule No slicing on the root elementelement.where(path.contains('.').not()).slicing.empty()
sdf-8aRule In any differential, all the elements must start with the StructureDefinition's specified type for non-logical models, or with the same type name for logical models(%resource.kind = 'logical' or element.first().path.startsWith(%resource.type)) and (element.tail().empty() or element.tail().all(path.startsWith(%resource.differential.element.first().path.replaceMatches('\\..*','')&'.')))
Affect this element
sdf-6Rule A structure must have either a differential, or a snapshot (or both)snapshot.exists() or differential.exists()
StructureDefinition.differential.element
Element IdStructureDefinition.differential.element
Definition

Captures constraints on each element within the resource.

Short DisplayDefinition of elements in the resource (if no StructureDefinition)
Cardinality1..*
TypeElementDefinition
Summaryfalse
Invariants
Affect this element
sdf-9Rule In any snapshot or differential, no label, code or requirements on 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()
sdf-15aRule If the first element in a differential has no "." in the path and it's not a logical model, it has no type(kind!='logical' and differential.element.first().path.contains('.').not()) implies differential.element.first().type.empty()
sdf-19Rule FHIR Specification models only use FHIR defined typesurl.startsWith('http://hl7.org/fhir/StructureDefinition') implies (differential | snapshot).element.type.code.all(matches('^[a-zA-Z0-9]+$') or matches('^http:\\/\\/hl7\\.org\\/fhirpath\\/System\\.[A-Z][A-Za-z]+$'))
sdf-17Rule All element definitions must have unique ids (diff)differential.element.all(id.exists()) and differential.element.id.trace('ids').isDistinct()
sdf-23Rule No slice name on root(snapshot | differential).element.all(path.contains('.').not() implies sliceName.empty())
sdf-22Rule FHIR Specification models never have default valuesurl.startsWith('http://hl7.org/fhir/StructureDefinition') implies (snapshot.element.defaultValue.empty() and differential.element.defaultValue.empty())
sdf-14Rule All element definitions must have an idsnapshot.element.all(id.exists()) and differential.element.all(id.exists())
sdf-21Rule Default values can only be specified on specializationsdifferential.element.defaultValue.exists() implies (derivation = 'specialization')
sdf-29Warning Elements in Resources must have a min cardinality or 0 or 1 and a max cardinality of 1 or *((kind in 'resource' | 'complex-type') and (derivation = 'specialization')) implies differential.element.where((min != 0 and min != 1) or (max != '1' and max != '*')).empty()
sdf-20Rule No slicing on the root elementelement.where(path.contains('.').not()).slicing.empty()
sdf-8aRule In any differential, all the elements must start with the StructureDefinition's specified type for non-logical models, or with the same type name for logical models(%resource.kind = 'logical' or element.first().path.startsWith(%resource.type)) and (element.tail().empty() or element.tail().all(path.startsWith(%resource.differential.element.first().path.replaceMatches('\\..*','')&'.')))