A request to convey information; e.g. the CDS system proposes that an alert be sent to a responsible provider, the CDS system proposes that the public health agency be notified about a reportable condition.

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 it's narrative along with other profiles, value sets, etc.

An Extension

STU3: CommunicationRequest.topic (new:Reference(Resource))

Element CommunicationRequest.topic has a context of CommunicationRequest based on following the parent source element upwards and mapping to CommunicationRequest. Element CommunicationRequest.topic has no mapping targets in FHIR R4B. Typically, this is because the element has been added (is a new element).

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 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.

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 status of the proposal or order.

The status of the communication request.

If true indicates that the CommunicationRequest is asking for the specified action to not occur.

The attributes provided with the request qualify what is not to be done.

STU3: CommunicationRequest.meta additional types (Meta) additional types from child elements (lastUpdated, profile, security, tag, versionId)

Element CommunicationRequest.meta is mapped to FHIR R4B element CommunicationRequest.meta as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.meta do not cover the following types: Meta. The mappings for CommunicationRequest.meta do not cover the following types based on type expansion: lastUpdated, profile, security, tag, versionId.

STU3: CommunicationRequest.text additional types (Narrative) additional types from child elements (div, status)

Element CommunicationRequest.text is mapped to FHIR R4B element CommunicationRequest.text as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.text do not cover the following types: Narrative. The mappings for CommunicationRequest.text do not cover the following types based on type expansion: div, status. 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.

STU3: CommunicationRequest.topic (new:Reference(Resource))

Element CommunicationRequest.topic has a context of CommunicationRequest based on following the parent source element upwards and mapping to CommunicationRequest. Element CommunicationRequest.topic has no mapping targets in FHIR R4B. Typically, this is because the element has been added (is a new element).

STU3: CommunicationRequest.identifier additional types (Identifier) additional types from child elements (assigner, period, system, type, use, value)

Element CommunicationRequest.identifier is mapped to FHIR R4B element CommunicationRequest.identifier as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.identifier do not cover the following types: Identifier. The mappings for CommunicationRequest.identifier do not cover the following types based on type expansion: assigner, period, system, type, use, value.

STU3: CommunicationRequest.basedOn additional types from child elements (display, identifier, reference)

Element CommunicationRequest.basedOn is mapped to FHIR R4B element CommunicationRequest.basedOn as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.basedOn do not cover the following types based on type expansion: display, identifier, reference. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.basedOn with unmapped reference targets: Resource.

STU3: CommunicationRequest.replaces additional types from child elements (display, identifier, reference)

Element CommunicationRequest.replaces is mapped to FHIR R4B element CommunicationRequest.replaces as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.replaces do not cover the following types based on type expansion: display, identifier, reference. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.replaces with unmapped reference targets: CommunicationRequest. The replacement could be because the initial request was immediately rejected (due to an issue) or because the previous request was completed, but the need for the action described by the request remains ongoing.

STU3: CommunicationRequest.groupIdentifier additional types (Identifier) additional types from child elements (assigner, period, system, type, use, value)

Element CommunicationRequest.groupIdentifier is mapped to FHIR R4B element CommunicationRequest.groupIdentifier as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.groupIdentifier do not cover the following types: Identifier. The mappings for CommunicationRequest.groupIdentifier do not cover the following types based on type expansion: assigner, period, system, type, use, value. Requests are linked either by a "basedOn" relationship (i.e. one request is fulfilling another) or by having a common requisition. Requests that are part of the same requisition are generally treated independently from the perspective of changing their state or maintaining them after initial creation.

STU3: CommunicationRequest.subject additional types from child elements (display, identifier, reference)

Element CommunicationRequest.subject is mapped to FHIR R4B element CommunicationRequest.subject as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.subject do not cover the following types based on type expansion: display, identifier, reference. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.subject with unmapped reference targets: Group, Patient.

STU3: CommunicationRequest.context additional types from child elements (display, identifier, reference)

Element CommunicationRequest.context is mapped to FHIR R4B element CommunicationRequest.encounter as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.context do not cover the following types based on type expansion: display, identifier, reference. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.context with unmapped reference targets: Encounter, EpisodeOfCare.

STU3: CommunicationRequest.payload.content[x] additional types (Attachment)

Element CommunicationRequest.payload.content[x] is mapped to FHIR R4B element CommunicationRequest.payload.content[x] as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.payload.content[x] do not cover the following types: Attachment. The target context CommunicationRequest.payload.content[x] is a choice-type element and cannot directly hold extensions. The context is moved up to parent element CommunicationRequest.payload. The standard extension alternate-reference has been mapped as PART of the representation of FHIR STU3 element CommunicationRequest.payload.content[x] with unmapped reference targets: Resource. Source element CommunicationRequest.payload.content[x] has unmapped reference types. While the target element CommunicationRequest.payload.content[x] is a choice type and does not allow extensions, the alternate-reference extension can be applied to Reference values within it.

STU3: CommunicationRequest.payload.content[x] additional types (Attachment)

Element CommunicationRequest.payload.content[x] is mapped to FHIR R4B element CommunicationRequest.payload.content[x] as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.payload.content[x] do not cover the following types: Attachment. The target context CommunicationRequest.payload.content[x] is a choice-type element and cannot directly hold extensions. The context is moved up to parent element CommunicationRequest.payload. The standard extension alternate-reference has been mapped as PART of the representation of FHIR STU3 element CommunicationRequest.payload.content[x] with unmapped reference targets: Resource. Source element CommunicationRequest.payload.content[x] has unmapped reference types. While the target element CommunicationRequest.payload.content[x] is a choice type and does not allow extensions, the alternate-reference extension can be applied to Reference values within it.

STU3: CommunicationRequest.requester.agent

Element CommunicationRequest.requester.agent is mapped to FHIR R4B element CommunicationRequest.requester as SourceIsBroaderThanTarget. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.requester.agent with unmapped reference targets: Device, Organization, Patient, Practitioner, RelatedPerson.

STU3: CommunicationRequest.requester.onBehalfOf (new:Reference(Organization))

Element CommunicationRequest.requester.onBehalfOf has a context of CommunicationRequest.requester based on following the parent source element upwards and mapping to CommunicationRequest. Element CommunicationRequest.requester.onBehalfOf has no mapping targets in FHIR R4B. Typically, this is because the element has been added (is a new element).

STU3: CommunicationRequest.recipient

Element CommunicationRequest.recipient is mapped to FHIR R4B element CommunicationRequest.recipient as SourceIsBroaderThanTarget. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.recipient with unmapped reference targets: CareTeam, Device, Group, Organization, Patient, Practitioner, RelatedPerson.

STU3: CommunicationRequest.sender

Element CommunicationRequest.sender is mapped to FHIR R4B element CommunicationRequest.sender as SourceIsBroaderThanTarget. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.sender with unmapped reference targets: Device, Organization, Patient, Practitioner, RelatedPerson.

STU3: CommunicationRequest.reasonReference additional types from child elements (display, identifier, reference)

Element CommunicationRequest.reasonReference is mapped to FHIR R4B element CommunicationRequest.reasonReference as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.reasonReference do not cover the following types based on type expansion: display, identifier, reference. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.reasonReference with unmapped reference targets: Condition, Observation.

STU3: CommunicationRequest.note additional types (Annotation) additional types from child elements (author[x], text, time)

Element CommunicationRequest.note is mapped to FHIR R4B element CommunicationRequest.note as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.note do not cover the following types: Annotation. The mappings for CommunicationRequest.note do not cover the following types based on type expansion: author[x], text, time.

A request to convey information; e.g. the CDS system proposes that an alert be sent to a responsible provider, the CDS system proposes that the public health agency be notified about a reportable condition.

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 might not always be associated with version changes to the resource.

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

An Extension

STU3: CommunicationRequest.meta additional types (Meta) additional types from child elements (lastUpdated, profile, security, tag, versionId)

Element CommunicationRequest.meta is mapped to FHIR R4B element CommunicationRequest.meta as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.meta do not cover the following types: Meta. The mappings for CommunicationRequest.meta do not cover the following types based on type expansion: lastUpdated, profile, security, tag, versionId.

The version specific identifier, as it appears in the version portion of the URL. This value changes when the resource is created, updated, or deleted.

The server assigns this value, and ignores what the client specifies, except in the case that the server is imposing version integrity on updates/deletes.

When the resource last changed - e.g. when the version changed.

This value is always populated except when the resource is first being created. The server / resource manager sets this value; what a client provides is irrelevant. This is equivalent to the HTTP Last-Modified and SHOULD have the same value on a read interaction.

A uri that identifies the source system of the resource. This provides a minimal amount of Provenance information that can be used to track or differentiate the source of information in the resource. The source may identify another FHIR server, document, message, database, etc.

In the provenance resource, this corresponds to Provenance.entity.what[x]. The exact use of the source (and the implied Provenance.entity.role) is left to implementer discretion. Only one nominated source is allowed; for additional provenance details, a full Provenance resource should be used.

This element can be used to indicate where the current master source of a resource that has a canonical URL if the resource is no longer hosted at the canonical URL.

A list of profiles (references to StructureDefinition resources) that this resource claims to conform to. The URL is a reference to StructureDefinition.url.

It is up to the server and/or other infrastructure of policy to determine whether/how these claims are verified and/or updated over time. The list of profile URLs is a set.

Security labels applied to this resource. These tags connect specific resources to the overall security policy and infrastructure.

The security labels can be updated without changing the stated version of the resource. The list of security labels is a set. Uniqueness is based the system/code, and version and display are ignored.

Tags applied to this resource. Tags are intended to be used to identify and relate resources to process and workflow, and applications are not required to consider the tags when interpreting the meaning of a resource.

The tags can be updated without changing the stated version of the resource. The list of tags is a set. Uniqueness is based the system/code, and version and display are ignored.

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 it's 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

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 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.

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

An Extension

STU3: CommunicationRequest.text additional types (Narrative) additional types from child elements (div, status)

Element CommunicationRequest.text is mapped to FHIR R4B element CommunicationRequest.text as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.text do not cover the following types: Narrative. The mappings for CommunicationRequest.text do not cover the following types based on type expansion: div, status. 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.

The status of the narrative - whether it's entirely generated (from just the defined data or the extensions too), or whether a human authored it and it may contain additional data.

The actual narrative content, a stripped down version of XHTML.

The contents of the html element are an XHTML fragment containing only the basic html formatting elements described in chapters 7-11 and 15 of the HTML 4.0 standard, <a> elements (either name or href), images and internally contained stylesheets. The XHTML content SHALL NOT contain a head, a body, external stylesheet references, scripts, forms, base/link/xlink, frames, iframes and objects.

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

An Extension

STU3: CommunicationRequest.topic (new:Reference(Resource))

Element CommunicationRequest.topic has a context of CommunicationRequest based on following the parent source element upwards and mapping to CommunicationRequest. Element CommunicationRequest.topic has no mapping targets in FHIR R4B. Typically, this is because the element has been added (is a new element).

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 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.

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.

Business identifiers assigned to this communication request by the performer or other systems which remain constant as the resource is updated and propagates from server to server.

This is a business identifier, not a resource identifier (see discussion). It is best practice for the identifier to only appear on a single resource instance, however business practices may occasionally dictate that multiple resource instances with the same identifier can exist - possibly even with different resource types. For example, multiple Patient and a Person resource instance might share the same social insurance number.

Allows identification of the communication request as it is known by various participating systems and in a way that remains consistent across servers.

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

An Extension

STU3: CommunicationRequest.identifier additional types (Identifier) additional types from child elements (assigner, period, system, type, use, value)

Element CommunicationRequest.identifier is mapped to FHIR R4B element CommunicationRequest.identifier as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.identifier do not cover the following types: Identifier. The mappings for CommunicationRequest.identifier do not cover the following types based on type expansion: assigner, period, system, type, use, value.

The purpose of this identifier.

Applications can assume that an identifier is permanent unless it explicitly says that it is temporary.

Allows the appropriate identifier for a particular context of use to be selected from among a set of identifiers.

A coded type for the identifier that can be used to determine which identifier to use for a specific purpose.

This element deals only with general categories of identifiers. It SHOULD not be used for codes that correspond 1..1 with the Identifier.system. Some identifiers may fall into multiple categories due to common usage. Where the system is known, a type is unnecessary because the type is always part of the system definition. However systems often need to handle identifiers where the system is not known. There is not a 1:1 relationship between type and system, since many different systems have the same type.

Allows users to make use of identifiers when the identifier system is not known.

Establishes the namespace for the value - that is, a URL that describes a set values that are unique.

Identifier.system is always case sensitive.

There are many sets of identifiers. To perform matching of two identifiers, we need to know what set we're dealing with. The system identifies a particular set of unique identifiers.

The portion of the identifier typically relevant to the user and which is unique within the context of the system.

If the value is a full URI, then the system SHALL be urn:ietf:rfc:3986. The value's primary purpose is computational mapping. As a result, it may be normalized for comparison purposes (e.g. removing non-significant whitespace, dashes, etc.) A value formatted for human display can be conveyed using the Rendered Value extension. Identifier.value is to be treated as case sensitive unless knowledge of the Identifier.system allows the processer to be confident that non-case-sensitive processing is safe.

Time period during which identifier is/was valid for use.

Organization that issued/manages the identifier.

The Identifier.assigner may omit the .reference element and only contain a .display element reflecting the name or other textual information about the assigning organization.

A plan or proposal that is fulfilled in whole or in part by this request.

Allows tracing of authorization for the request and tracking whether proposals/recommendations were acted upon.

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

An Extension

STU3: CommunicationRequest.basedOn additional types from child elements (display, identifier, reference)

Element CommunicationRequest.basedOn is mapped to FHIR R4B element CommunicationRequest.basedOn as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.basedOn do not cover the following types based on type expansion: display, identifier, reference. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.basedOn with unmapped reference targets: Resource.

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.

The expected type of the target of the reference. If both Reference.type and Reference.reference are populated and Reference.reference is a FHIR URL, both SHALL be consistent.

The type is the Canonical URL of Resource Definition that is the type this reference refers to. References are URLs that are relative to http://hl7.org/fhir/StructureDefinition/ e.g. "Patient" is a reference to http://hl7.org/fhir/StructureDefinition/Patient. Absolute URLs are only allowed for logical models (and can only be used in references in logical models, not resources).

This element is used to indicate the type of the target of the reference. This may be used which ever of the other elements are populated (or not). In some cases, the type of the target may be determined by inspection of the reference (e.g. a RESTful URL) or by resolving the target of the reference; if both the type and a reference is provided, the reference SHALL resolve to a resource of the same type as that specified.

An identifier for the target resource. This is used when there is no way to reference the other resource directly, either because the entity it represents 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.

Reference is intended to point to a structure that can potentially be expressed as a FHIR resource, though there is no need for it to exist as an actual FHIR resource instance - except in as much as an application wishes to actual find the target of the reference. The content referred to be the identifier must meet the logical constraints implied by any limitations on what resource types are permitted for the reference. For example, it would not be legitimate to send the identifier for a drug prescription if the type were Reference(Observation|DiagnosticReport). One of the use-cases for Reference.identifier is the situation where no FHIR representation exists (where the type is Reference (Any).

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.

Completed or terminated request(s) whose function is taken by this new request.

The replacement could be because the initial request was immediately rejected (due to an issue) or because the previous request was completed, but the need for the action described by the request remains ongoing.

Allows tracing the continuation of a therapy or administrative process instantiated through multiple requests.

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

An Extension

STU3: CommunicationRequest.replaces additional types from child elements (display, identifier, reference)

Element CommunicationRequest.replaces is mapped to FHIR R4B element CommunicationRequest.replaces as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.replaces do not cover the following types based on type expansion: display, identifier, reference. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.replaces with unmapped reference targets: CommunicationRequest. The replacement could be because the initial request was immediately rejected (due to an issue) or because the previous request was completed, but the need for the action described by the request remains ongoing.

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.

The expected type of the target of the reference. If both Reference.type and Reference.reference are populated and Reference.reference is a FHIR URL, both SHALL be consistent.

The type is the Canonical URL of Resource Definition that is the type this reference refers to. References are URLs that are relative to http://hl7.org/fhir/StructureDefinition/ e.g. "Patient" is a reference to http://hl7.org/fhir/StructureDefinition/Patient. Absolute URLs are only allowed for logical models (and can only be used in references in logical models, not resources).

This element is used to indicate the type of the target of the reference. This may be used which ever of the other elements are populated (or not). In some cases, the type of the target may be determined by inspection of the reference (e.g. a RESTful URL) or by resolving the target of the reference; if both the type and a reference is provided, the reference SHALL resolve to a resource of the same type as that specified.

An identifier for the target resource. This is used when there is no way to reference the other resource directly, either because the entity it represents 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.

Reference is intended to point to a structure that can potentially be expressed as a FHIR resource, though there is no need for it to exist as an actual FHIR resource instance - except in as much as an application wishes to actual find the target of the reference. The content referred to be the identifier must meet the logical constraints implied by any limitations on what resource types are permitted for the reference. For example, it would not be legitimate to send the identifier for a drug prescription if the type were Reference(Observation|DiagnosticReport). One of the use-cases for Reference.identifier is the situation where no FHIR representation exists (where the type is Reference (Any).

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.

A shared identifier common to all requests that were authorized more or less simultaneously by a single author, representing the identifier of the requisition, prescription or similar form.

Requests are linked either by a "basedOn" relationship (i.e. one request is fulfilling another) or by having a common requisition. Requests that are part of the same requisition are generally treated independently from the perspective of changing their state or maintaining them after initial creation.

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

An Extension

STU3: CommunicationRequest.groupIdentifier additional types (Identifier) additional types from child elements (assigner, period, system, type, use, value)

Element CommunicationRequest.groupIdentifier is mapped to FHIR R4B element CommunicationRequest.groupIdentifier as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.groupIdentifier do not cover the following types: Identifier. The mappings for CommunicationRequest.groupIdentifier do not cover the following types based on type expansion: assigner, period, system, type, use, value. Requests are linked either by a "basedOn" relationship (i.e. one request is fulfilling another) or by having a common requisition. Requests that are part of the same requisition are generally treated independently from the perspective of changing their state or maintaining them after initial creation.

The purpose of this identifier.

Applications can assume that an identifier is permanent unless it explicitly says that it is temporary.

Allows the appropriate identifier for a particular context of use to be selected from among a set of identifiers.

A coded type for the identifier that can be used to determine which identifier to use for a specific purpose.

This element deals only with general categories of identifiers. It SHOULD not be used for codes that correspond 1..1 with the Identifier.system. Some identifiers may fall into multiple categories due to common usage. Where the system is known, a type is unnecessary because the type is always part of the system definition. However systems often need to handle identifiers where the system is not known. There is not a 1:1 relationship between type and system, since many different systems have the same type.

Allows users to make use of identifiers when the identifier system is not known.

Establishes the namespace for the value - that is, a URL that describes a set values that are unique.

Identifier.system is always case sensitive.

There are many sets of identifiers. To perform matching of two identifiers, we need to know what set we're dealing with. The system identifies a particular set of unique identifiers.

The portion of the identifier typically relevant to the user and which is unique within the context of the system.

If the value is a full URI, then the system SHALL be urn:ietf:rfc:3986. The value's primary purpose is computational mapping. As a result, it may be normalized for comparison purposes (e.g. removing non-significant whitespace, dashes, etc.) A value formatted for human display can be conveyed using the Rendered Value extension. Identifier.value is to be treated as case sensitive unless knowledge of the Identifier.system allows the processer to be confident that non-case-sensitive processing is safe.

Time period during which identifier is/was valid for use.

Organization that issued/manages the identifier.

The Identifier.assigner may omit the .reference element and only contain a .display element reflecting the name or other textual information about the assigning organization.

The status of the proposal or order.

The status of the communication request.

Captures the reason for the current state of the CommunicationRequest.

This is generally only used for "exception" statuses such as "suspended" or "cancelled". The reason why the CommunicationRequest was created at all is captured in reasonCode, not here. [distinct reason codes for different statuses can be enforced using invariants if they are universal bindings].

Codes identifying the reason for the current state of a request.

The type of message to be sent such as alert, notification, reminder, instruction, etc.

There may be multiple axes of categorization and one communication request may serve multiple purposes.

Codes for general categories of communications such as alerts, instruction, etc.

Characterizes how quickly the proposed act must be initiated. Includes concepts such as stat, urgent, routine.

Codes indicating the relative importance of a communication request.

If true indicates that the CommunicationRequest is asking for the specified action to not occur.

The attributes provided with the request qualify what is not to be done.

A channel that was used for this communication (e.g. email, fax).

Codes for communication mediums such as phone, fax, email, in person, etc.

The patient or group that is the focus of this communication request.

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

An Extension

STU3: CommunicationRequest.subject additional types from child elements (display, identifier, reference)

Element CommunicationRequest.subject is mapped to FHIR R4B element CommunicationRequest.subject as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.subject do not cover the following types based on type expansion: display, identifier, reference. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.subject with unmapped reference targets: Group, Patient.

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.

The expected type of the target of the reference. If both Reference.type and Reference.reference are populated and Reference.reference is a FHIR URL, both SHALL be consistent.

The type is the Canonical URL of Resource Definition that is the type this reference refers to. References are URLs that are relative to http://hl7.org/fhir/StructureDefinition/ e.g. "Patient" is a reference to http://hl7.org/fhir/StructureDefinition/Patient. Absolute URLs are only allowed for logical models (and can only be used in references in logical models, not resources).

This element is used to indicate the type of the target of the reference. This may be used which ever of the other elements are populated (or not). In some cases, the type of the target may be determined by inspection of the reference (e.g. a RESTful URL) or by resolving the target of the reference; if both the type and a reference is provided, the reference SHALL resolve to a resource of the same type as that specified.

An identifier for the target resource. This is used when there is no way to reference the other resource directly, either because the entity it represents 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.

Reference is intended to point to a structure that can potentially be expressed as a FHIR resource, though there is no need for it to exist as an actual FHIR resource instance - except in as much as an application wishes to actual find the target of the reference. The content referred to be the identifier must meet the logical constraints implied by any limitations on what resource types are permitted for the reference. For example, it would not be legitimate to send the identifier for a drug prescription if the type were Reference(Observation|DiagnosticReport). One of the use-cases for Reference.identifier is the situation where no FHIR representation exists (where the type is Reference (Any).

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.

Other resources that pertain to this communication request and to which this communication request should be associated.

Don't use CommunicationRequest.about element when a more specific element exists, such as basedOn, reasonReference, or replaces.

The Encounter during which this CommunicationRequest was created or to which the creation of this record is tightly associated.

This will typically be the encounter the event occurred within, but some activities may be initiated prior to or after the official completion of an encounter but still be tied to the context of the encounter.

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

An Extension

STU3: CommunicationRequest.context additional types from child elements (display, identifier, reference)

Element CommunicationRequest.context is mapped to FHIR R4B element CommunicationRequest.encounter as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.context do not cover the following types based on type expansion: display, identifier, reference. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.context with unmapped reference targets: Encounter, EpisodeOfCare.

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.

The expected type of the target of the reference. If both Reference.type and Reference.reference are populated and Reference.reference is a FHIR URL, both SHALL be consistent.

The type is the Canonical URL of Resource Definition that is the type this reference refers to. References are URLs that are relative to http://hl7.org/fhir/StructureDefinition/ e.g. "Patient" is a reference to http://hl7.org/fhir/StructureDefinition/Patient. Absolute URLs are only allowed for logical models (and can only be used in references in logical models, not resources).

This element is used to indicate the type of the target of the reference. This may be used which ever of the other elements are populated (or not). In some cases, the type of the target may be determined by inspection of the reference (e.g. a RESTful URL) or by resolving the target of the reference; if both the type and a reference is provided, the reference SHALL resolve to a resource of the same type as that specified.

An identifier for the target resource. This is used when there is no way to reference the other resource directly, either because the entity it represents 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.

Reference is intended to point to a structure that can potentially be expressed as a FHIR resource, though there is no need for it to exist as an actual FHIR resource instance - except in as much as an application wishes to actual find the target of the reference. The content referred to be the identifier must meet the logical constraints implied by any limitations on what resource types are permitted for the reference. For example, it would not be legitimate to send the identifier for a drug prescription if the type were Reference(Observation|DiagnosticReport). One of the use-cases for Reference.identifier is the situation where no FHIR representation exists (where the type is Reference (Any).

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.

Text, attachment(s), or resource(s) to be communicated to the recipient.

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

An Extension

STU3: CommunicationRequest.payload.content[x] additional types (Attachment)

Element CommunicationRequest.payload.content[x] is mapped to FHIR R4B element CommunicationRequest.payload.content[x] as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.payload.content[x] do not cover the following types: Attachment. The target context CommunicationRequest.payload.content[x] is a choice-type element and cannot directly hold extensions. The context is moved up to parent element CommunicationRequest.payload. The standard extension alternate-reference has been mapped as PART of the representation of FHIR STU3 element CommunicationRequest.payload.content[x] with unmapped reference targets: Resource. Source element CommunicationRequest.payload.content[x] has unmapped reference types. While the target element CommunicationRequest.payload.content[x] is a choice type and does not allow extensions, the alternate-reference extension can be applied to Reference values within it.

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 manageable, 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 communicated content (or for multi-part communications, one portion of the communication).

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 manageable, 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.

STU3: CommunicationRequest.payload.content[x] additional types (Attachment)

Element CommunicationRequest.payload.content[x] is mapped to FHIR R4B element CommunicationRequest.payload.content[x] as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.payload.content[x] do not cover the following types: Attachment. The target context CommunicationRequest.payload.content[x] is a choice-type element and cannot directly hold extensions. The context is moved up to parent element CommunicationRequest.payload. The standard extension alternate-reference has been mapped as PART of the representation of FHIR STU3 element CommunicationRequest.payload.content[x] with unmapped reference targets: Resource. Source element CommunicationRequest.payload.content[x] has unmapped reference types. While the target element CommunicationRequest.payload.content[x] is a choice type and does not allow extensions, the alternate-reference extension can be applied to Reference values within it.

The time when this communication is to occur.

For draft requests, indicates the date of initial creation. For requests with other statuses, indicates the date of activation.

The device, individual, or organization who initiated the request and has responsibility for its activation.

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

An Extension

STU3: CommunicationRequest.requester.agent

Element CommunicationRequest.requester.agent is mapped to FHIR R4B element CommunicationRequest.requester as SourceIsBroaderThanTarget. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.requester.agent with unmapped reference targets: Device, Organization, Patient, Practitioner, RelatedPerson.

STU3: CommunicationRequest.requester.onBehalfOf (new:Reference(Organization))

Element CommunicationRequest.requester.onBehalfOf has a context of CommunicationRequest.requester based on following the parent source element upwards and mapping to CommunicationRequest. Element CommunicationRequest.requester.onBehalfOf has no mapping targets in FHIR R4B. Typically, this is because the element has been added (is a new element).

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.

The expected type of the target of the reference. If both Reference.type and Reference.reference are populated and Reference.reference is a FHIR URL, both SHALL be consistent.

The type is the Canonical URL of Resource Definition that is the type this reference refers to. References are URLs that are relative to http://hl7.org/fhir/StructureDefinition/ e.g. "Patient" is a reference to http://hl7.org/fhir/StructureDefinition/Patient. Absolute URLs are only allowed for logical models (and can only be used in references in logical models, not resources).

This element is used to indicate the type of the target of the reference. This may be used which ever of the other elements are populated (or not). In some cases, the type of the target may be determined by inspection of the reference (e.g. a RESTful URL) or by resolving the target of the reference; if both the type and a reference is provided, the reference SHALL resolve to a resource of the same type as that specified.

An identifier for the target resource. This is used when there is no way to reference the other resource directly, either because the entity it represents 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.

Reference is intended to point to a structure that can potentially be expressed as a FHIR resource, though there is no need for it to exist as an actual FHIR resource instance - except in as much as an application wishes to actual find the target of the reference. The content referred to be the identifier must meet the logical constraints implied by any limitations on what resource types are permitted for the reference. For example, it would not be legitimate to send the identifier for a drug prescription if the type were Reference(Observation|DiagnosticReport). One of the use-cases for Reference.identifier is the situation where no FHIR representation exists (where the type is Reference (Any).

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.

The entity (e.g. person, organization, clinical information system, device, group, or care team) which is the intended target of the communication.

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

An Extension

STU3: CommunicationRequest.recipient

Element CommunicationRequest.recipient is mapped to FHIR R4B element CommunicationRequest.recipient as SourceIsBroaderThanTarget. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.recipient with unmapped reference targets: CareTeam, Device, Group, Organization, Patient, Practitioner, 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.

The expected type of the target of the reference. If both Reference.type and Reference.reference are populated and Reference.reference is a FHIR URL, both SHALL be consistent.

The type is the Canonical URL of Resource Definition that is the type this reference refers to. References are URLs that are relative to http://hl7.org/fhir/StructureDefinition/ e.g. "Patient" is a reference to http://hl7.org/fhir/StructureDefinition/Patient. Absolute URLs are only allowed for logical models (and can only be used in references in logical models, not resources).

This element is used to indicate the type of the target of the reference. This may be used which ever of the other elements are populated (or not). In some cases, the type of the target may be determined by inspection of the reference (e.g. a RESTful URL) or by resolving the target of the reference; if both the type and a reference is provided, the reference SHALL resolve to a resource of the same type as that specified.

An identifier for the target resource. This is used when there is no way to reference the other resource directly, either because the entity it represents 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.

Reference is intended to point to a structure that can potentially be expressed as a FHIR resource, though there is no need for it to exist as an actual FHIR resource instance - except in as much as an application wishes to actual find the target of the reference. The content referred to be the identifier must meet the logical constraints implied by any limitations on what resource types are permitted for the reference. For example, it would not be legitimate to send the identifier for a drug prescription if the type were Reference(Observation|DiagnosticReport). One of the use-cases for Reference.identifier is the situation where no FHIR representation exists (where the type is Reference (Any).

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.

The entity (e.g. person, organization, clinical information system, or device) which is to be the source of the communication.

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

An Extension

STU3: CommunicationRequest.sender

Element CommunicationRequest.sender is mapped to FHIR R4B element CommunicationRequest.sender as SourceIsBroaderThanTarget. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.sender with unmapped reference targets: Device, Organization, Patient, Practitioner, 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.

The expected type of the target of the reference. If both Reference.type and Reference.reference are populated and Reference.reference is a FHIR URL, both SHALL be consistent.

The type is the Canonical URL of Resource Definition that is the type this reference refers to. References are URLs that are relative to http://hl7.org/fhir/StructureDefinition/ e.g. "Patient" is a reference to http://hl7.org/fhir/StructureDefinition/Patient. Absolute URLs are only allowed for logical models (and can only be used in references in logical models, not resources).

This element is used to indicate the type of the target of the reference. This may be used which ever of the other elements are populated (or not). In some cases, the type of the target may be determined by inspection of the reference (e.g. a RESTful URL) or by resolving the target of the reference; if both the type and a reference is provided, the reference SHALL resolve to a resource of the same type as that specified.

An identifier for the target resource. This is used when there is no way to reference the other resource directly, either because the entity it represents 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.

Reference is intended to point to a structure that can potentially be expressed as a FHIR resource, though there is no need for it to exist as an actual FHIR resource instance - except in as much as an application wishes to actual find the target of the reference. The content referred to be the identifier must meet the logical constraints implied by any limitations on what resource types are permitted for the reference. For example, it would not be legitimate to send the identifier for a drug prescription if the type were Reference(Observation|DiagnosticReport). One of the use-cases for Reference.identifier is the situation where no FHIR representation exists (where the type is Reference (Any).

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.

Describes why the request is being made in coded or textual form.

Textual reasons can be captured using reasonCode.text.

Codes for describing reasons for the occurrence of a communication.

Indicates another resource whose existence justifies this request.

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

An Extension

STU3: CommunicationRequest.reasonReference additional types from child elements (display, identifier, reference)

Element CommunicationRequest.reasonReference is mapped to FHIR R4B element CommunicationRequest.reasonReference as SourceIsBroaderThanTarget. The mappings for CommunicationRequest.reasonReference do not cover the following types based on type expansion: display, identifier, reference. The standard extension alternate-reference has been mapped as the representation of FHIR STU3 element CommunicationRequest.reasonReference with unmapped reference targets: Condition, Observation.

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.