A set of healthcare-related information that is assembled together into a single logical document that provides a single coherent statement of meaning, establishes its own context and that has clinical attestation with regard to who is making the statement. While a Composition defines the structure, it does not actually contain the content: rather the full content of a document is contained in a Bundle, of which the Composition is the first resource contained.

While the focus of this specification is on patient-specific clinical statements, this resource can also apply to other healthcare-related statements such as study protocol designs, healthcare invoices and other activities that are not necessarily patient-specific or clinical.

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

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

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

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

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 workflow/clinical status of this composition. The status is a marker for the clinical standing of the document.

If a composition is marked as withdrawn, the compositions/documents in the series, or data from the composition or document series, should never be displayed to a user without being clearly marked as untrustworthy. The flag "entered-in-error" is why this element is labeled as a modifier of other elements.

Some reporting work flows require that the original narrative of a final document never be altered; instead, only new narrative can be added. The composition resource has no explicit status for explicitly noting whether this business rule is in effect. This would be handled by an extension if required.

The workflow/clinical status of the composition.

Need to be able to mark interim, amended, or withdrawn compositions or documents.

Specifies the particular kind of composition (e.g. History and Physical, Discharge Summary, Progress Note). This usually equates to the purpose of making the composition.

For Composition type, LOINC is ubiquitous and strongly endorsed by HL7. Most implementation guides will require a specific LOINC code, or use LOINC as an extensible binding.

Type of a composition.

Key metadata element describing the composition, used in searching/filtering.

Who or what the composition is about. The composition can be about a person, (patient or healthcare practitioner), a device (e.g. a machine) or even a group of subjects (such as a document about a herd of livestock, or a set of patients that share a common exposure).

For clinical documents, this is usually the patient.

Essential metadata for searching for the composition. Identifies who and/or what the composition/document is about.

The composition editing time, when the composition was last logically changed by the author.

The Last Modified Date on the composition may be after the date of the document was attested without being changed.

dateTime is used for tracking, organizing versions and searching.

Identifies who is responsible for the information in the composition, not necessarily who typed it in.

Identifies who is responsible for the content.

An Extension

R4: Composition.author

Element Composition.author is mapped to FHIR STU3 element Composition.author as SourceIsBroaderThanTarget. The standard extension alternate-reference has been mapped as the representation of FHIR R4 element Composition.author with unmapped reference targets: Organization, PractitionerRole.

Official human-readable label for the composition.

For many compositions, the title is the same as the text or a display name of Composition.type (e.g. a "consultation" or "progress note"). Note that CDA does not make title mandatory, but there are no known cases where it is useful for title to be omitted, so it is mandatory here. Feedback on this requirement is welcome during the trial use period.

The code specifying the level of confidentiality of the Composition.

The exact use of this element, and enforcement and issues related to highly sensitive documents are out of scope for the base specification, and delegated to implementation profiles (see security section).

This element is labeled as a modifier because highly confidential documents must not be treated as if they are not.

Codes specifying the level of confidentiality of the composition.

R4: Composition.author

Element Composition.author is mapped to FHIR STU3 element Composition.author as SourceIsBroaderThanTarget. The standard extension alternate-reference has been mapped as the representation of FHIR R4 element Composition.author with unmapped reference targets: Organization, PractitionerRole.

R4: Composition.attester.party

Element Composition.attester.party is mapped to FHIR STU3 element Composition.attester.party as SourceIsBroaderThanTarget. The standard extension alternate-reference has been mapped as the representation of FHIR R4 element Composition.attester.party with unmapped reference targets: PractitionerRole, RelatedPerson.

R4: Composition.section.author (new:Reference(Practitioner,PractitionerRole,Device,Patient,RelatedPerson,Organization))

Element Composition.section.author has a context of Composition.section based on following the parent source element upwards and mapping to Composition. Element Composition.section.author has no mapping targets in FHIR STU3. Typically, this is because the element has been added (is a new element).

R4: Composition.section.focus (new:Reference(Resource))

Element Composition.section.focus has a context of Composition.section based on following the parent source element upwards and mapping to Composition. Element Composition.section.focus has no mapping targets in FHIR STU3. Typically, this is because the element has been added (is a new element). Typically, sections in a doument are about the subject of the document, whether that is a patient, or group of patients, location, or device, or whatever. For some kind of documents, some sections actually contain data about related entities. Typical examples are a section in a newborn discharge summary concerning the mother, or family history documents, with a section about each family member, though there are many other examples.

A set of healthcare-related information that is assembled together into a single logical document that provides a single coherent statement of meaning, establishes its own context and that has clinical attestation with regard to who is making the statement. While a Composition defines the structure, it does not actually contain the content: rather the full content of a document is contained in a Bundle, of which the Composition is the first resource contained.

While the focus of this specification is on patient-specific clinical statements, this resource can also apply to other healthcare-related statements such as study protocol designs, healthcare invoices and other activities that are not necessarily patient-specific or clinical.

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

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

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

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

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

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

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).

A human language.

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

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

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

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.

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

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. Usually modifier elements provide negation or qualification. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

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.

Logical identifier for the composition, assigned when created. This identifier stays constant as the composition is changed over time.

See discussion in resource definition for how these relate.

The workflow/clinical status of this composition. The status is a marker for the clinical standing of the document.

If a composition is marked as withdrawn, the compositions/documents in the series, or data from the composition or document series, should never be displayed to a user without being clearly marked as untrustworthy. The flag "entered-in-error" is why this element is labeled as a modifier of other elements.

Some reporting work flows require that the original narrative of a final document never be altered; instead, only new narrative can be added. The composition resource has no explicit status for explicitly noting whether this business rule is in effect. This would be handled by an extension if required.

The workflow/clinical status of the composition.

Need to be able to mark interim, amended, or withdrawn compositions or documents.

Specifies the particular kind of composition (e.g. History and Physical, Discharge Summary, Progress Note). This usually equates to the purpose of making the composition.

For Composition type, LOINC is ubiquitous and strongly endorsed by HL7. Most implementation guides will require a specific LOINC code, or use LOINC as an extensible binding.

Type of a composition.

Key metadata element describing the composition, used in searching/filtering.

A categorization for the type of the composition - helps for indexing and searching. This may be implied by or derived from the code specified in the Composition Type.

This is a metadata field from XDS/MHD.

High-level kind of a clinical document at a macro level.

Helps humans to assess whether the composition is of interest when viewing an index of compositions or documents.

Who or what the composition is about. The composition can be about a person, (patient or healthcare practitioner), a device (e.g. a machine) or even a group of subjects (such as a document about a herd of livestock, or a set of patients that share a common exposure).

For clinical documents, this is usually the patient.

Essential metadata for searching for the composition. Identifies who and/or what the composition/document is about.

Describes the clinical encounter or type of care this documentation is associated with.

Provides context for the composition and supports searching.

The composition editing time, when the composition was last logically changed by the author.

The Last Modified Date on the composition may be after the date of the document was attested without being changed.

dateTime is used for tracking, organizing versions and searching.

Identifies who is responsible for the information in the composition, not necessarily who typed it in.

Identifies who is responsible for the content.

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

An Extension

R4: Composition.author

Element Composition.author is mapped to FHIR STU3 element Composition.author as SourceIsBroaderThanTarget. The standard extension alternate-reference has been mapped as the representation of FHIR R4 element Composition.author with unmapped reference targets: Organization, PractitionerRole.

A reference to a location at which the other resource is found. The reference may be a relative reference, in which case it is relative to the service base URL, or an absolute URL that resolves to the location where the resource is found. The reference may be version specific or not. If the reference is not to a FHIR RESTful server, then it should be assumed to be version specific. Internal fragment references (start with '#') refer to contained resources.

Using absolute URLs provides a stable scalable approach suitable for a cloud/web context, while using relative/logical references provides a flexible approach suitable for use when trading across closed eco-system boundaries. Absolute URLs do not need to point to a FHIR RESTful server, though this is the preferred approach. If the URL conforms to the structure "/[type]/[id]" then it should be assumed that the reference is to a FHIR RESTful server.

An identifier for the other resource. This is used when there is no way to reference the other resource directly, either because the entity is not available through a FHIR server, or because there is no way for the author of the resource to convert a known identifier to an actual location. There is no requirement that a Reference.identifier point to something that is actually exposed as a FHIR instance, but it SHALL point to a business concept that would be expected to be exposed as a FHIR instance, and that instance would need to be of a FHIR resource type allowed by the reference.

When an identifier is provided in place of a reference, any system processing the reference will only be able to resolve the identifier to a reference if it understands the business context in which the identifier is used. Sometimes this is global (e.g. a national identifier) but often it is not. For this reason, none of the useful mechanisms described for working with references (e.g. chaining, includes) are possible, nor should servers be expected to be able resolve the reference. Servers may accept an identifier based reference untouched, resolve it, and/or reject it - see CapabilityStatement.rest.resource.referencePolicy.

When both an identifier and a literal reference are provided, the literal reference is preferred. Applications processing the resource are allowed - but not required - to check that the identifier matches the literal reference

Applications converting a logical reference to a literal reference may choose to leave the logical reference present, or remove it.

Plain text narrative that identifies the resource in addition to the resource reference.

This is generally not the same as the Resource.text of the referenced resource. The purpose is to identify what's being referenced, not to fully describe it.

Official human-readable label for the composition.

For many compositions, the title is the same as the text or a display name of Composition.type (e.g. a "consultation" or "progress note"). Note that CDA does not make title mandatory, but there are no known cases where it is useful for title to be omitted, so it is mandatory here. Feedback on this requirement is welcome during the trial use period.

The code specifying the level of confidentiality of the Composition.

The exact use of this element, and enforcement and issues related to highly sensitive documents are out of scope for the base specification, and delegated to implementation profiles (see security section).

This element is labeled as a modifier because highly confidential documents must not be treated as if they are not.

Codes specifying the level of confidentiality of the composition.

A participant who has attested to the accuracy of the composition/document.

Only list each attester once.

Identifies responsibility for the accuracy of the composition content.

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. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

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 that contains it. Usually modifier elements provide negation or qualification. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

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 type of attestation the authenticator offers.

Use more than one code where a single attester has more than one mode (professional and legal are often paired).

The way in which a person authenticated a composition.

Indicates the level of authority of the attestation.

When the composition was attested by the party.

Identifies when the information in the composition was deemed accurate. (Things may have changed since then.).

Who attested the composition in the specified way.

Identifies who has taken on the responsibility for accuracy of the composition content.

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

An Extension

R4: Composition.attester.party

Element Composition.attester.party is mapped to FHIR STU3 element Composition.attester.party as SourceIsBroaderThanTarget. The standard extension alternate-reference has been mapped as the representation of FHIR R4 element Composition.attester.party with unmapped reference targets: PractitionerRole, RelatedPerson.

A reference to a location at which the other resource is found. The reference may be a relative reference, in which case it is relative to the service base URL, or an absolute URL that resolves to the location where the resource is found. The reference may be version specific or not. If the reference is not to a FHIR RESTful server, then it should be assumed to be version specific. Internal fragment references (start with '#') refer to contained resources.

Using absolute URLs provides a stable scalable approach suitable for a cloud/web context, while using relative/logical references provides a flexible approach suitable for use when trading across closed eco-system boundaries. Absolute URLs do not need to point to a FHIR RESTful server, though this is the preferred approach. If the URL conforms to the structure "/[type]/[id]" then it should be assumed that the reference is to a FHIR RESTful server.

An identifier for the other resource. This is used when there is no way to reference the other resource directly, either because the entity is not available through a FHIR server, or because there is no way for the author of the resource to convert a known identifier to an actual location. There is no requirement that a Reference.identifier point to something that is actually exposed as a FHIR instance, but it SHALL point to a business concept that would be expected to be exposed as a FHIR instance, and that instance would need to be of a FHIR resource type allowed by the reference.

When an identifier is provided in place of a reference, any system processing the reference will only be able to resolve the identifier to a reference if it understands the business context in which the identifier is used. Sometimes this is global (e.g. a national identifier) but often it is not. For this reason, none of the useful mechanisms described for working with references (e.g. chaining, includes) are possible, nor should servers be expected to be able resolve the reference. Servers may accept an identifier based reference untouched, resolve it, and/or reject it - see CapabilityStatement.rest.resource.referencePolicy.

When both an identifier and a literal reference are provided, the literal reference is preferred. Applications processing the resource are allowed - but not required - to check that the identifier matches the literal reference

Applications converting a logical reference to a literal reference may choose to leave the logical reference present, or remove it.

Plain text narrative that identifies the resource in addition to the resource reference.

This is generally not the same as the Resource.text of the referenced resource. The purpose is to identify what's being referenced, not to fully describe it.

Identifies the organization or group who is responsible for ongoing maintenance of and access to the composition/document information.

This is useful when documents are derived from a composition - provides guidance for how to get the latest version of the document. This is optional because this is sometimes not known by the authoring system, and can be inferred by context. However, it is important that this information be known when working with a derived document, so providing a custodian is encouraged.

Identifies where to go to find the current version, where to report issues, etc.

Relationships that this composition has with other compositions or documents that already exist.

A document is a version specific composition.

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. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

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 that contains it. Usually modifier elements provide negation or qualification. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

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 type of relationship that this composition has with anther composition or document.

If this document appends another document, then the document cannot be fully understood without also accessing the referenced document.

The type of relationship between documents.

The target composition/document of this relationship.

The clinical service, such as a colonoscopy or an appendectomy, being documented.

The event needs to be consistent with the type element, though can provide further information if desired.

Provides context for the composition and creates a linkage between a resource describing an event and the composition created describing the event.

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. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.

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 that contains it. Usually modifier elements provide negation or qualification. In order to make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer is allowed to define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension. Applications processing a resource are required to check for modifier extensions.

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.

This list of codes represents the main clinical acts, such as a colonoscopy or an appendectomy, being documented. In some cases, the event is inherent in the typeCode, such as a "History and Physical Report" in which the procedure being documented is necessarily a "History and Physical" act.

An event can further specialize the act inherent in the typeCode, such as where it is simply "Procedure Report" and the procedure was a "colonoscopy". If one or more eventCodes are included, they SHALL NOT conflict with the values inherent in the classCode, practiceSettingCode or typeCode, as such a conflict would create an ambiguous situation. This short list of codes is provided to be used as key words for certain types of queries.

This list of codes represents the main clinical acts being documented.

The period of time covered by the documentation. There is no assertion that the documentation is a complete representation for this period, only that it documents events during this time.

The description and/or reference of the event(s) being documented. For example, this could be used to document such a colonoscopy or an appendectomy.

The root of the sections that make up the composition.

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

An Extension

R4: Composition.section.author (new:Reference(Practitioner,PractitionerRole,Device,Patient,RelatedPerson,Organization))

Element Composition.section.author has a context of Composition.section based on following the parent source element upwards and mapping to Composition. Element Composition.section.author has no mapping targets in FHIR STU3. Typically, this is because the element has been added (is a new element).

R4: Composition.section.focus (new:Reference(Resource))

Element Composition.section.focus has a context of Composition.section based on following the parent source element upwards and mapping to Composition. Element Composition.section.focus has no mapping targets in FHIR STU3. Typically, this is because the element has been added (is a new element). Typically, sections in a doument are about the subject of the document, whether that is a patient, or group of patients, location, or device, or whatever. For some kind of documents, some sections actually contain data about related entities. Typical examples are a section in a newborn discharge summary concerning the mother, or family history documents, with a section about each family member, though there are many other examples.

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

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 label for this particular section. This will be part of the rendered content for the document, and is often used to build a table of contents.

The title identifies the section for a human reader. The title must be consistent with the narrative of the resource that is the target of the section.content reference. Generally, sections SHOULD have titles, but in some documents, it is unnecessary or inappropriate. Typically, this is where a section has subsections that have their own adequately distinguishing title, or documents that only have a single section. Most Implementation Guides will make section title to be a required element.

Section headings are often standardized for different types of documents. They give guidance to humans on how the document is organized.

A code identifying the kind of content contained within the section. This must be consistent with the section title.

The code identifies the section for an automated processor of the document. This is particularly relevant when using profiles to control the structure of the document. If the section has content (instead of sub-sections), the section.code does not change the meaning or interpretation of the resource that is the content of the section in the comments for the section.code.

Classification of a section of a composition/document.

Provides computable standardized labels to topics within the document.

A human-readable narrative that contains the attested content of the section, 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.

Document profiles may define what content should be represented in the narrative to ensure clinical safety.

How the entry list was prepared - whether it is a working list that is suitable for being maintained on an ongoing basis, or if it represents a snapshot of a list of items from another source, or whether it is a prepared list where items may be marked as added, modified or deleted.

This element is labeled as a modifier because a change list must not be mis-understood as a complete list.

The processing mode that applies to this section.

Sections are used in various ways, and it must be known in what way it is safe to use the entries in them.

Specifies the order applied to the items in the section entries.

Applications SHOULD render ordered lists in the order provided, but MAY allow users to re-order based on their own preferences as well. If there is no order specified, the order is unknown, though there may still be some order.

What order applies to the items in the entry.

Important for presentation and rendering. Lists may be sorted to place more important information first or to group related entries.

A reference to the actual resource from which the narrative in the section is derived.

If there are no entries in the list, an emptyReason SHOULD be provided.

If the section is empty, why the list is empty. An empty section typically has some text explaining the empty reason.

The various reasons for an empty section make a significant interpretation to its interpretation. Note that this code is for use when the entire section content has been suppressed, and not for when individual items are omitted - implementers may consider using a text note or a flag on an entry in these cases.

If a section is empty, why it is empty.

Allows capturing things like "none exist" or "not asked" which can be important for most lists.

A nested sub-section within this section.

Nested sections are primarily used to help human readers navigate to particular portions of the document.