US Core Implementation Guide (Release 1.1.0 Ballot )

This page is part of the US Core (v1.1.0: STU2 Ballot 1) based on FHIR R3. The current version which supercedes this version is 5.0.1. For a full list of available versions, see the Directory of published versions

D.4.1.4 StructureDefinition: - Detailed Descriptions

Definitions for the StructureDefinition-us-core-documentreference Profile.

DocumentReference
Definition

This is a basic constraint on DocumentRefernce for use in the US Core IG.

Control0..*
Comments

Usually, this is used for documents other than those defined by FHIR.

InvariantsDefined on this element
dom-1: If the resource is contained in another resource, it SHALL NOT contain any narrative (: contained.text.empty())
dom-2: If the resource is contained in another resource, it SHALL NOT contain nested Resources (: contained.contained.empty())
dom-3: If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource (: contained.where(('#'+id in %resource.descendants().reference).not()).empty())
dom-4: If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated (: contained.meta.versionId.empty() and contained.meta.lastUpdated.empty())
DocumentReference.id
Definition

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

Control0..1
Typeid
Comments

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

DocumentReference.meta
Definition

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

Control0..1
TypeMeta
DocumentReference.implicitRules
Definition

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

Control0..1
Typeuri
Is Modifiertrue
Comments

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

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

DocumentReference.language
Definition

The base language in which the resource is written.

Control0..1
BindingA human language.
The codes SHALL be taken from Common Languages; other codes may be used where these codes are not suitable
Typecode
Comments

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

DocumentReference.text
Definition

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

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

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

DocumentReference.contained
Definition

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

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

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

DocumentReference.extension
Definition

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

Control0..*
TypeExtension
Alternate Namesextensions, user content
Comments

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

DocumentReference.modifierExtension
Definition

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

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

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

DocumentReference.masterIdentifier
Definition

Document identifier as assigned by the source of the document. This identifier is specific to this version of the document. This unique identifier may be used elsewhere to identify this version of the document.

Control0..1
TypeIdentifier
Requirements

The structure and format of this Id shall be consistent with the specification corresponding to the formatCode attribute. (e.g. for a DICOM standard document a 64-character numeric UID, for an HL7 CDA format a serialization of the CDA Document Id extension and root in the form "oid^extension", where OID is a 64 digits max, and the Id is a 16 UTF-8 char max. If the OID is coded without the extension then the '^' character shall not be included.).

Comments

CDA Document Id extension and root.

DocumentReference.identifier
Definition

Other identifiers associated with the document, including version independent identifiers.

NoteThis is a business identifer, not a resource identifier (see discussion)
Control0..1
TypeIdentifier
Must Supporttrue
DocumentReference.status
Definition

The status of this document reference.

Control1..1
BindingThe codes SHALL be taken from DocumentReferenceStatus
Typecode
Is Modifiertrue
Must Supporttrue
Comments

This is the status of the DocumentReference object, which might be independent from the docStatus element.

This element is labeled as a modifier because the status contains the codes that mark the document or reference as not currently valid.

DocumentReference.docStatus
Definition

The status of the underlying document.

Control0..1
BindingStatus of the underlying document.
The codes SHALL be taken from CompositionStatus
Typecode
Comments

The document that is pointed to might be in various lifecycle states.

DocumentReference.type
Definition

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

Control1..1
BindingProvider role codes consisting of NUCC Health Care Provider Taxonomy Code Set for providers.
The codes SHALL be taken from Document Type Value Set
TypeCodeableConcept
Must Supporttrue
Comments

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

DocumentReference.class
Definition

A categorization for the type of document referenced - helps for indexing and searching. This may be implied by or derived from the code specified in the DocumentReference.type.

Control0..1
BindingHigh-level kind of a clinical document at a macro level.
For example codes, see Document Class Value Set
TypeCodeableConcept
Requirements

Helps humans to assess whether the document is of interest when viewing a list of documents.

Alternate Nameskind
Comments

This is a metadata field from XDS/MHD.

DocumentReference.subject
Definition

Who or what the document is about. The document 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 farm animals, or a set of patients that share a common exposure).

Control1..1
TypeReference(US Core Patient Profile)
Must Supporttrue
DocumentReference.created
Definition

When the document was created.

Control0..1
TypedateTime
Must Supporttrue
Comments

Creation time is used for tracking, organizing versions and searching. This is the creation time of the document, not the source material on which it is based.

DocumentReference.indexed
Definition

When the document reference was created.

Control1..1
Typeinstant
Comments

Referencing/indexing time is used for tracking, organizing versions and searching.

DocumentReference.author
Definition

Identifies who is responsible for adding the information to the document.

Control0..*
TypeChoice of: Reference(Practitioner), Reference(Organization), Reference(Device), Reference(Patient), Reference(RelatedPerson)
Comments

Not necessarily who did the actual data entry (i.e. typist) it in or who was the source (informant).

DocumentReference.authenticator
Definition

Which person or organization authenticates that this document is valid.

Control0..1
TypeChoice of: Reference(Practitioner), Reference(Organization)
Comments

Represents a participant within the author institution who has legally authenticated or attested the document. Legal authentication implies that a document has been signed manually or electronically by the legal Authenticator.

DocumentReference.custodian
Definition

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

Control0..1
TypeReference(Organization)
Comments

Identifies the logical organization to go to find the current version, where to report issues, etc. This is different from the physical location of the document, which is the technical location of the document, which host may be delegated to the management of some other organization.

DocumentReference.relatesTo
Definition

Relationships that this document has with other document references that already exist.

Control0..*
TypeBackboneElement
Is Modifiertrue
Comments

This element is labeled as a modifier because documents that append to other documents are incomplete on their own.

InvariantsDefined on this element
ele-1: All FHIR elements must have a @value or children (: hasValue() | (children().count() > id.count()))
DocumentReference.relatesTo.id
Definition

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

Control0..1
Typestring
DocumentReference.relatesTo.extension
Definition

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

Control0..*
TypeExtension
Alternate Namesextensions, user content
Comments

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

DocumentReference.relatesTo.modifierExtension
Definition

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

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

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

DocumentReference.relatesTo.code
Definition

The type of relationship that this document has with anther document.

Control1..1
BindingThe type of relationship between documents.
The codes SHALL be taken from DocumentRelationshipType
Typecode
Comments

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

DocumentReference.relatesTo.target
Definition

The target document of this relationship.

Control1..1
TypeReference(DocumentReference)
DocumentReference.description
Definition

Human-readable description of the source document. This is sometimes known as the "title".

Control0..1
Typestring
Requirements

Helps humans to assess whether the document is of interest.

Comments

What the document is about, rather than a terse summary of the document. It is commonly the case that records do not have a title and are collectively referred to by the display name of Record code (e.g. a "consultation" or "progress note").

DocumentReference.securityLabel
Definition

A set of Security-Tag codes specifying the level of privacy/security of the Document. Note that DocumentReference.meta.security contains the security labels of the "reference" to the document, while DocumentReference.securityLabel contains a snapshot of the security labels on the document the reference refers to.

Control0..*
BindingSecurity Labels from the Healthcare Privacy and Security Classification System.
The codes SHALL be taken from All Security Labels; other codes may be used where these codes are not suitable
TypeCodeableConcept
Requirements

Use of the Health Care Privacy/Security Classification (HCS) system of security-tag use is recommended.

Comments

The confidentiality codes can carry multiple vocabulary items. HL7 has developed an understanding of security and privacy tags that might be desirable in a Document Sharing environment, called HL7 Healthcare Privacy and Security Classification System (HCS). The following specification is recommended but not mandated, as the vocabulary bindings are an administrative domain responsibility. The use of this method is up to the policy domain such as the XDS Affinity Domain or other Trust Domain where all parties including sender and recipients are trusted to appropriately tag and enforce. In the HL7 Healthcare Privacy and Security Classification (HCS) there are code systems specific to Confidentiality, Sensitivity, Integrity, and Handling Caveats. Some values would come from a local vocabulary as they are related to workflow roles and special projects.

DocumentReference.content
Definition

The document and format referenced. There may be multiple content element repetitions, each with a different format.

Control1..1
TypeBackboneElement
Must Supporttrue
InvariantsDefined on this element
ele-1: All FHIR elements must have a @value or children (: hasValue() | (children().count() > id.count()))
DocumentReference.content.id
Definition

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

Control0..1
Typestring
DocumentReference.content.extension
Definition

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

Control0..*
TypeExtension
Alternate Namesextensions, user content
Comments

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

DocumentReference.content.modifierExtension
Definition

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

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

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

DocumentReference.content.attachment
Definition

The document or URL of the document along with critical metadata to prove content has integrity.

Control1..1
TypeAttachment
Must Supporttrue
DocumentReference.content.attachment.id
Definition

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

Control0..1
Typestring
DocumentReference.content.attachment.extension
Definition

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

Control0..*
TypeExtension
Alternate Namesextensions, user content
Comments

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

DocumentReference.content.attachment.contentType
Definition

Identifies the type of the data in the attachment and allows a method to be chosen to interpret or render the data. Includes mime type parameters such as charset where appropriate.

Control1..1
BindingThe mime type of an attachment. Any valid mime type is allowed.
The codes SHALL be taken from http://www.rfc-editor.org/bcp/bcp13.txt
Typecode
Must Supporttrue
Requirements

Processors of the data need to be able to know how to interpret the data.

Example
General:text/plain; charset=UTF-8, image/png
DocumentReference.content.attachment.language
Definition

The human language of the content. The value can be any valid value according to BCP 47.

Control0..1
BindingA human language.
The codes SHALL be taken from Common Languages; other codes may be used where these codes are not suitable
Typecode
Requirements

Users need to be able to choose between the languages in a set of attachments.

Example
General:en-AU
DocumentReference.content.attachment.data
Definition

The actual data of the attachment - a sequence of bytes. In XML, represented using base64.

Control0..1
Typebase64Binary
Requirements

The data needs to able to be transmitted inline.

Comments

The base64-encoded data SHALL be expressed in the same character set as the base resource XML or JSON.

DocumentReference.content.attachment.url
Definition

An alternative location where the data can be accessed.

Control1..1
Typeuri
Must Supporttrue
Requirements

The data needs to be transmitted by reference.

Comments

If both data and url are provided, the url SHALL point to the same content as the data contains. Urls may be relative references or may reference transient locations such as a wrapping envelope using cid: though this has ramifications for using signatures. Relative URLs are interpreted relative to the service url, like a resource reference, rather than relative to the resource itself. If a URL is provided, it SHALL resolve to actual data.

Example
General:http://www.acme.com/logo-small.png
DocumentReference.content.attachment.size
Definition

The number of bytes of data that make up this attachment (before base64 encoding, if that is done).

Control0..1
TypeunsignedInt
Requirements

Representing the size allows applications to determine whether they should fetch the content automatically in advance, or refuse to fetch it at all.

Comments

The number of bytes is redundant if the data is provided as a base64binary, but is useful if the data is provided as a url reference.

DocumentReference.content.attachment.hash
Definition

The calculated hash of the data using SHA-1. Represented using base64.

Control0..1
Typebase64Binary
Requirements

Included so that applications can verify that the contents of a location have not changed and so that a signature of the content can implicitly sign the content of an image without having to include the data in the instance or reference the url in the signature.

Comments

The hash is calculated on the data prior to base64 encoding, if the data is based64 encoded.

DocumentReference.content.attachment.title
Definition

A label or set of text to display in place of the data.

Control0..1
Typestring
Requirements

Applications need a label to display to a human user in place of the actual data if the data cannot be rendered or perceived by the viewer.

Example
General:Official Corporate Logo
DocumentReference.content.attachment.creation
Definition

The date that the attachment was first created.

Control0..1
TypedateTime
Requirements

This is often tracked as an integrity issue for use of the attachment.

DocumentReference.content.format
Definition

An identifier of the document encoding, structure, and template that the document conforms to beyond the base format indicated in the mimeType.

Control1..1
BindingThe codes SHALL be taken from DocumentReference Format Code Set; other codes may be used where these codes are not suitable
TypeCoding
Must Supporttrue
Comments

Note that while IHE mostly issues URNs for format types, not all documents can be identified by a URI.

DocumentReference.context
Definition

The clinical context in which the document was prepared.

Control0..1
TypeBackboneElement
Must Supporttrue
Comments

These values are primarily added to help with searching for interesting/relevant documents.

InvariantsDefined on this element
ele-1: All FHIR elements must have a @value or children (: hasValue() | (children().count() > id.count()))
DocumentReference.context.id
Definition

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

Control0..1
Typestring
DocumentReference.context.extension
Definition

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

Control0..*
TypeExtension
Alternate Namesextensions, user content
Comments

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

DocumentReference.context.modifierExtension
Definition

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

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

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

DocumentReference.context.encounter
Definition

Describes the clinical encounter or type of care that the document content is associated with.

Control0..1
TypeReference(US Core Encounter Profile)
Must Supporttrue
DocumentReference.context.event
Definition

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.

Control0..*
BindingThis list of codes represents the main clinical acts being documented.
For example codes, see v3 Code System ActCode
TypeCodeableConcept
Comments

An event can further specialize the act inherent in the type, such as where it is simply "Procedure Report" and the procedure was a "colonoscopy". If one or more event codes are included, they shall not conflict with the values inherent in the class or type elements as such a conflict would create an ambiguous situation.

DocumentReference.context.period
Definition

The time period over which the service that is described by the document was provided.

Control0..1
TypePeriod
DocumentReference.context.facilityType
Definition

The kind of facility where the patient was seen.

Control0..1
BindingXDS Facility Type.
For example codes, see Facility Type Code Value Set
TypeCodeableConcept
DocumentReference.context.practiceSetting
Definition

This property may convey specifics about the practice setting where the content was created, often reflecting the clinical specialty.

Control0..1
BindingAdditional details about where the content was created (e.g. clinical specialty).
For example codes, see Practice Setting Code Value Set
TypeCodeableConcept
Requirements

This is an important piece of metadata that providers often rely upon to quickly sort and/or filter out to find specific content.

Comments

The value set for this content has an example binding because it is a value set decided by community policy. Other examples exist for consideration: * HITSP created the table HITSP/C80 Table 2-148 Clinical Specialty Value Set (a value set based upon SNOMED CT which is referenced by Direct (XDR and XDM for Direct Messaging Specification, Version 1), as well as Nationwide Health Information Network (NHIN). Query for Documents, Web Service Interface Specification, V 3.0, 07/27/2011 * ELGA (Austria) (ELGA CDA Implementie-rungsleitfäden Registrierung von CDA Dokumenten für ELGA mit IHE Cross-Enterprise Document Sharing: XDS Metadaten (XDSDocumentEntry), [1.2.40.0.34.7.6.3] * XDS Connect-a-thon practiceSettingCode.

DocumentReference.context.sourcePatientInfo
Definition

The Patient Information as known when the document was published. May be a reference to a version specific, or contained.

Control0..1
TypeReference(Patient)
DocumentReference.context.related
Definition

Related identifiers or resources associated with the DocumentReference.

Control0..*
TypeBackboneElement
Comments

May be identifiers or resources that caused the DocumentReference or referenced Document to be created.

InvariantsDefined on this element
ele-1: All FHIR elements must have a @value or children (: hasValue() | (children().count() > id.count()))
DocumentReference.context.related.id
Definition

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

Control0..1
Typestring
DocumentReference.context.related.extension
Definition

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

Control0..*
TypeExtension
Alternate Namesextensions, user content
Comments

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

DocumentReference.context.related.modifierExtension
Definition

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

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

There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.

DocumentReference.context.related.identifier
Definition

Related identifier to this DocumentReference. If both id and ref are present they shall refer to the same thing.

NoteThis is a business identifer, not a resource identifier (see discussion)
Control0..1
TypeIdentifier
Comments

Order numbers, accession numbers, XDW workflow numbers.

DocumentReference.context.related.ref
Definition

Related Resource to this DocumentReference. If both id and ref are present they shall refer to the same thing.

Control0..1
TypeReference(Resource)
Comments

Order, ProcedureRequest, Procedure, EligibilityRequest, etc.