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.

A reference to a set of rules that were followed when the resource was constructed, and which must be understood when processing the content. Often, this is a reference to an implementation guide that defines the special rules along with other profiles etc.

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. Often, when used, the URL is a reference to an implementation guide that defines these special rules as part of its narrative along with other profiles, value sets, etc.

These resources do not have an independent existence apart from the resource that contains them - they cannot be identified independently, nor can they have their own independent transaction scope. This is allowed to be a Parameters resource if and only if it is referenced by a resource that provides context/meaning.

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. Contained resources may have profiles and tags in their meta elements, but SHALL NOT have security labels.

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 and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer 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.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

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.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

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.

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.

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

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.

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.

Support human navigation and code generation.

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

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

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

The lifecycle status of an artifact.

Defines the kind of structure that this definition is describing.

Defines the type of structure that a definition is describing.

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.

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.

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.

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'.

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

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.

How the type relates to the baseDefinition.

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).

How a type relates to its baseDefinition.

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

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 in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

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.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

Captures constraints on each element within the resource.

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.

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

Within the context of the FHIR RESTful interactions, the resource has an id except for cases like the create and conditional update. Otherwise, the use of the resouce id depends on the given use case.

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

A reference to a set of rules that were followed when the resource was constructed, and which must be understood when processing the content. Often, this is a reference to an implementation guide that defines the special rules along with other profiles etc.

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. Often, when used, the URL is a reference to an implementation guide that defines these special rules as part of its narrative along with other profiles, value sets, etc.

The base language in which the resource is written.

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).

IETF language tag for a human language

A human-readable narrative that contains a summary of the resource and can 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.

Contained resources do not have a 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 information is added later.

These resources do not have an independent existence apart from the resource that contains them - they cannot be identified independently, nor can they have their own independent transaction scope. This is allowed to be a Parameters resource if and only if it is referenced by a resource that provides context/meaning.

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. Contained resources may have profiles and tags in their meta elements, but SHALL NOT have security labels.

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

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.

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 and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer 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.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

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.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

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.

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.

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

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.

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.

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

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').

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.

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

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.

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.

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.

Support human navigation and code generation.

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

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.

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

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

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

The lifecycle status of an artifact.

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.

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

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

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.

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

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.

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

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

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

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

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

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).

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.

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

Assist in searching for appropriate content.

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

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.)

Countries and regions within which this artifact is targeted for use.

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

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.

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.

...

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

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').

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.

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

(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.

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

Codes for the meaning of the defined structure (SNOMED CT and LOINC codes, as an example).

Assist in searching for appropriate StructureDefinitions.

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.

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.

All published FHIR Versions.

An external specification that the content is mapped to.

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

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

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.

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 in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

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.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

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

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

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

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

A name for the specification that is being mapped to.

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

Defines the kind of structure that this definition is describing.

Defines the type of structure that a definition is describing.

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.

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.

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.

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

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

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.

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 in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

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.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

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

How an extension context is interpreted.

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

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.

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.

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.

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'.

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

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.

How the type relates to the baseDefinition.

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).

How a type relates to its baseDefinition.

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

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

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

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.

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 in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

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.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

Captures constraints on each element within the resource.

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

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

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

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.

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 in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

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.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

Captures constraints on each element within the resource.

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

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

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.

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 in which it is contained and/or the understanding of the containing element's descendants. Usually modifier elements provide negation or qualification. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

Modifier extensions SHALL NOT change the meaning of any elements on Resource or DomainResource (including cannot change the meaning of modifierExtension itself).

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.

Modifier extensions allow for extensions that cannot be safely ignored to be clearly distinguished from the vast majority of extensions which can be safely ignored. This promotes interoperability by eliminating the need for implementers to prohibit the presence of extensions. For further information, see the definition of modifier extensions.

The path identifies the element and is expressed as a "."-separated list of ancestor elements, beginning with the name of the resource or extension.

Codes that define how this element is represented in instances, when the deviation varies from the normal case. No extensions are allowed on elements with a representation of 'xmlAttr', no matter what FHIR serialization format is used.

In resources, this is rarely used except for special cases where the representation deviates from the normal, and can only be done in the base standard (and profiles must reproduce what the base standard does). This element is used quite commonly in Logical models when the logical models represent a specific serialization format (e.g. CDA, v2 etc.).

How a property is represented when serialized.

The name of this element definition slice, when slicing is working. The name must be a token with no dots or spaces. This is a unique name referring to a specific set of constraints applied to this element, used to provide a name to different slices of the same element.

The name SHALL be unique within the structure within the context of the constrained resource element. (Though to avoid confusion, uniqueness across all elements is recommended.).

May also be used for code generation purposes.

If true, indicates that this slice definition is constraining a slice definition with the same name in an inherited profile. If false, the slice is not overriding any slice in an inherited profile. If missing, the slice might or might not be overriding a slice in an inherited profile, depending on the sliceName.

If set to true, an ancestor profile SHALL have a slicing definition with this name. If set to false, no ancestor profile is permitted to have a slicing definition with this name.

Allows detection of a situation where an ancestor profile adds or removes slicing with the same name where that might impact the child profile.

A single preferred label which is the text to display beside the element indicating its meaning or to use to prompt for the element in a user display or form.

See also the extension http://hl7.org/fhir/StructureDefinition/elementdefinition-question.

A code that has the same meaning as the element in a particular terminology.

The concept SHALL be properly aligned with the data element definition and other constraints, as defined in the code system, including relationships, of any code listed here. Where multiple codes exist in a terminology that could correspond to the data element, the most granular code(s) should be selected, so long as they are not more restrictive than the data element itself. The mappings may be used to provide more or less granular or structured equivalences in the code system.

Codes that indicate the meaning of a data element.

Links the meaning of an element to an external terminology, and is very useful for searching and indexing.

Indicates that the element is sliced into a set of alternative definitions (i.e. in a structure definition, there are multiple different constraints on a single element in the base resource). Slicing can be used in any resource that has cardinality ..* on the base resource, or any resource with a choice of types. The set of slices is any elements that come after this in the element sequence that have the same path, until a shorter path occurs (the shorter path terminates the set).

The first element in the sequence, the one that carries the slicing, is the definition that applies to all the slices. This is based on the unconstrained element, but can apply any constraints as appropriate. This may include the common constraints on the children of the element.

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

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

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.

Designates which child elements are used to discriminate between the slices when processing an instance. If one or more discriminators are provided, the value of the child elements in the instance data SHALL completely distinguish which slice the element in the resource matches based on the allowed values for those elements in each of the slices.

If there is no discriminator, the content is hard to process, so this should be avoided.

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

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

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.

How the element value is interpreted when discrimination is evaluated.

'pattern' is deprecated - it works exactly the same as 'value'.

How an element value is interpreted when discrimination is evaluated.

A FHIRPath expression, using the simple subset of FHIRPath, that is used to identify the element on which discrimination is based.

A human-readable text description of how the slicing works. If there is no discriminator, this is required to be present to provide whatever information is possible about how the slices can be differentiated.

If it's really not possible to differentiate them, the design should be re-evaluated to make the content usable.

If the matching elements have to occur in the same order as defined in the profile.

Order should only be required when it is a pressing concern for presentation. Profile authors should consider making the order a feature of the rules about the narrative, not the rules about the data - requiring ordered data makes the profile much less re-usable.

Whether additional slices are allowed or not. When the slices are ordered, profile authors can also say that additional slices are only allowed at the end.

Allowing additional elements makes for a much for flexible template - it's open for use in wider contexts, but also means that the content of the resource is not closed, and applications have to decide how to handle content not described by the profile.

How slices are interpreted when evaluating an instance.

A concise description of what this element means (e.g. for use in autogenerated summaries).

It is easy for a different short definition to change the meaning of an element and this can have nasty downstream consequences. Please be careful when providing short definitions in a profile.

Provides a complete explanation of the meaning of the data element for human readability. For the case of elements derived from existing elements (e.g. constraints), the definition SHALL be consistent with the base definition, but convey the meaning of the element in the particular context of use of the resource. (Note: The text you are reading is specified in ElementDefinition.definition).

It is easy for a different definition to change the meaning of an element and this can have nasty downstream consequences. Please be careful when providing definitions in a profile.

To allow a user to state the usage of an element in a particular context.

Explanatory notes and implementation guidance about the data element, including notes about how to use the data properly, exceptions to proper use, etc. (Note: The text you are reading is specified in ElementDefinition.comment).

If it is possible to capture usage rules using constraints, that mechanism should be used in preference to this element.

This element is for traceability of why the element was created and why the constraints exist as they do. This may be used to point to source materials or specifications that drove the structure of this element.

This element does not describe the usage of the element (that's done in comments), rather it's for traceability of why the element is either needed or why the constraints exist as they do. This may be used to point to source materials or specifications that drove the structure of this data element.

Identifies additional names by which this element might also be known.

Allows for better easier recognition of the element by multiple communities, including international communities.

The minimum number of times this element SHALL appear in the instance.

The maximum number of times this element is permitted to appear in the instance.

Information about the base definition of the element, provided to make it unnecessary for tools to trace the deviation of the element through the derived and related profiles. When the element definition is not the original definition of an element - e.g. either in a constraint on another type, or for elements from a super type in a snap shot - then the information in provided in the element definition may be different to the base definition. On the original definition of the element, it will be same.

The base information does not carry any information that could not be determined from the path and related profiles, but making this determination requires both that the related profiles are available, and that the algorithm to determine them be available. For tooling simplicity, the base information must always be populated in element definitions in snap shots, even if it is the same.

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

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

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.

The Path that identifies the base element - this matches the ElementDefinition.path for that element. Across FHIR, there is only one base definition of any element - that is, an element definition on a StructureDefinition without a StructureDefinition.base.

Minimum cardinality of the base element identified by the path.

This is provided for consistency with max, and may affect code generation of mandatory elements of the base resource are generated differently (some reference implementations have done this).

Maximum cardinality of the base element identified by the path.

This is provided to code generation, since the serialization representation in JSON differs depending on whether the base element has max > 1. Also, some forms of code generation may differ.

Identifies an element defined elsewhere in the definition whose content rules should be applied to the current element. ContentReferences bring across all the rules that are in the ElementDefinition for the element, including definitions, cardinality constraints, bindings, invariants etc.

ContentReferences can only be defined in specializations, not constrained types, and they cannot be changed and always reference the non-constrained definition.

The data type or resource that the value of this element is permitted to be.

The Type of the element can be left blank in a differential constraint, in which case the type is inherited from the resource. Abstract types are not permitted to appear as a type when multiple types are listed. (I.e. Abstract types cannot be part of a choice).

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

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

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.

URL of Data type or Resource that is a(or the) type used for this element. 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.

If the element is a reference to another resource, this element contains "Reference", and the targetProfile element defines what resources can be referenced. The targetProfile may be a reference to the general definition of a resource (e.g. http://hl7.org/fhir/StructureDefinition/Patient).

Identifies a profile structure or implementation Guide that applies to the datatype this element refers to. If any profiles are specified, then the content must conform to at least one of them. The URL can be a local reference - to a contained StructureDefinition, or a reference to another StructureDefinition or Implementation Guide by a canonical URL. When an implementation guide is specified, the type SHALL conform to at least one profile defined in the implementation guide.

It is possible to profile backbone element (e.g. part of a resource), using the http://hl7.org/fhir/StructureDefinition/elementdefinition-profile-element extension.

Used when the type is "Reference" or "canonical", and identifies a profile structure or implementation Guide that applies to the target of the reference this element refers to. If any profiles are specified, then the content must conform to at least one of them. The URL can be a local reference - to a contained StructureDefinition, or a reference to another StructureDefinition or Implementation Guide by a canonical URL. When an implementation guide is specified, the target resource SHALL conform to at least one profile defined in the implementation guide.

If the type is a reference to another resource, how the resource is or can be aggregated - is it a contained resource, or a reference, and if the context is a bundle, is it included in the bundle.

See Aggregation Rules for further clarification.

How resource references can be aggregated.

Whether this reference needs to be version specific or version independent, or whether either can be used.

The base specification never makes a rule as to which form is allowed, but implementation guides may do this. See Aggregation Rules for further clarification.

Whether a reference needs to be version specific or version independent, or whether either can be used.

The value that should be used if there is no value stated in the instance (e.g. 'if not otherwise specified, the abstract is false').

Specifying a default value means that the property can never been unknown - it must always have a value. Further, the default value can never be changed, or changed in constraints on content models. Defining default values creates many difficulties in implementation (e.g. when is a value missing?). For these reasons, default values are (and should be) used extremely sparingly.

No default values are ever defined in the FHIR specification, nor can they be defined in constraints ("profiles") on data types or resources. This element only exists so that default values may be defined in logical models.

The Implicit meaning that is to be understood when this element is missing (e.g. 'when this element is missing, the period is ongoing').

Implicit meanings for missing values can only be specified on a resource, data type, or extension definition, and never in a profile that applies to one of these. An implicit meaning for a missing value can never be changed, and specifying one has the consequence that constraining its use in profiles eliminates use cases as possibilities, not merely moving them out of scope.

If present, indicates that the order of the repeating element has meaning and describes what that meaning is. If absent, it means that the order of the element has no meaning.

This element can only be asserted on repeating elements and can only be introduced when defining resources or data types. It can be further refined profiled elements but if absent in the base type, a profile cannot assert meaning.

Specifies a value that SHALL be exactly the value for this element in the instance, if present. For purposes of comparison, non-significant whitespace is ignored, and all values must be an exact match (case and accent sensitive). Missing elements/attributes must also be missing.

This is not recommended for Coding and CodeableConcept since these often have highly contextual properties such as version or display.

Specifies a value that each occurrence of the element in the instance SHALL follow - that is, any value in the pattern must be found in the instance, if the element has a value. Other additional values may be found too. This is effectively constraint by example.

When pattern[x] is used to constrain a primitive, it means that the value provided in the pattern[x] must match the instance value exactly.

When an element within a pattern[x] is used to constrain an array, it means that each element provided in the pattern[x] must (recursively) match at least one element from the instance array.

When pattern[x] is used to constrain a complex object, it means that each property in the pattern must be present in the complex object, and its value must recursively match -- i.e.,

1. If primitive: it must match exactly the pattern value
2. If a complex object: it must match (recursively) the pattern value
3. If an array: it must match (recursively) the pattern value

If a pattern[x] is declared on a repeating element, the pattern applies to all repetitions. If the desire is for a pattern to apply to only one element or a subset of elements, slicing must be used. See Examples of Patterns for examples of pattern usage and the effect it will have.

Mostly used for fixing values of CodeableConcept. In general, pattern[x] is not intended for use with primitive types, where is has the same meaning as fixed[x].

A sample value for this element demonstrating the type of information that would typically be found in the element.

Examples will most commonly be present for data where it's not implicitly obvious from either the data type or value set what the values might be. (I.e. Example values for dates or quantities would generally be unnecessary.) If the example value is fully populated, the publication tool can generate an instance automatically.

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

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

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.

Describes the purpose of this example among the set of examples.

The actual value for the element, which must be one of the types allowed for this element.

The minimum allowed value for the element. The value is inclusive. This is allowed for the types date, dateTime, instant, time, decimal, integer, and Quantity.

Except for date/date/instant, the type of the minValue[x] SHALL be the same as the specified type of the element. For the date/dateTime/instant values, the type of minValue[x] SHALL be either the same, or a Duration which specifies a relative time limit to the current time. The duration value is positive, and is subtracted from the current clock to determine the minimum allowable value. A minimum value for a Quantity is interpreted as a canonical minimum - e.g. you cannot provide 100mg if the minimum value is 10g.

The maximum allowed value for the element. The value is inclusive. This is allowed for the types date, dateTime, instant, time, decimal, integer, and Quantity.

Except for date/date/instant, the type of the maxValue[x] SHALL be the same as the specified type of the element. For the date/dateTime/instant values, the type of maxValue[x] SHALL be either the same, or a Duration which specifies a relative time limit to the current time. The duration value is positive, and is added to the current clock to determine the maximum allowable value. A maximum value for a Quantity is interpreted as a canonical maximum - e.g. you cannot provide 10g if the maximum value is 50mg.