Complex
Primitive
ActivityDefinition
CapabilityStatement
CodeSystem
Composition
ConceptMap
Encounter
Library
List
Measure
MessageHeader
Observation
Patient
PlanDefinition
Questionnaire
Resource
ServiceDefinition
StructureDefinition
StructureMap
ValueSet
default
Base StructureDefinition for Reference Type
Reference
Path
Reference
Id
Reference
Cardinality
0 - *
Definition
A reference from one resource to another.
Comment
References SHALL be a reference to an actual FHIR resource, and SHALL be resolveable (allowing for access control, temporary unavailability, etc). Resolution can be either by retrieval from the URL, or, where applicable by resource type, by treating an absolute reference as a canonical URL and looking it up in a local registry/repository.
Constraint
ele-1 [error]
All FHIR elements must have a @value or children
ref-1 [error]
SHALL have a contained resource if a local reference is provided
Condition
ele-1
Path
Reference.reference
Id
Reference.reference
Type
Cardinality
0 - 1
Definition
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.
Comment
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.
Condition
ref-1
Path
Reference.identifier
Id
Reference.identifier
Type
Cardinality
0 - 1
Definition
An identifier for the other resource. This is used when there is no way to reference the other resource directly, either because the entity is not available through a FHIR server, or because there is no way for the author of the resource to convert a known identifier to an actual location. There is no requirement that a Reference.identifier point to something that is actually exposed as a FHIR instance, but it SHALL point to a business concept that would be expected to be exposed as a FHIR instance, and that instance would need to be of a FHIR resource type allowed by the reference.
Comment
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.
Path
Reference.identifier.Identifier.use
Id
Identifier.use
Type
Cardinality
0 - 1
Definition
The purpose of this identifier.
Comment
This is labeled as "Is Modifier" because applications should not mistake a temporary id for a permanent one. Applications can assume that an identifier is permanent unless it explicitly says that it is temporary.
Requirements
Allows the appropriate identifier for a particular context of use to be selected from among a set of identifiers.
Path
Reference.identifier.Identifier.type
Id
Identifier.type
Type
Cardinality
0 - 1
Definition
A coded type for the identifier that can be used to determine which identifier to use for a specific purpose.
Comment
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.
Requirements
Allows users to make use of identifiers when the identifier system is not known.
Path
Reference.identifier.Identifier.type.CodeableConcept.coding
Id
CodeableConcept.coding
Type
Cardinality
0 - *
Definition
A reference to a code defined by a terminology system.
Comment
Codes may be defined very casually in enumerations, or code lists, up to very formal definitions such as SNOMED CT - see the HL7 v3 Core Principles for more information. Ordering of codings is undefined and SHALL NOT be used to infer meaning. Generally, at most only one of the coding values will be labeled as UserSelected = true.
Requirements
Allows for translations and alternate encodings within a code system. Also supports communication of the same instance to systems requiring different encodings.
Path
Reference.identifier.Identifier.type.CodeableConcept.coding.Coding.system
Id
Coding.system
Type
Cardinality
0 - 1
Definition
The identification of the code system that defines the meaning of the symbol in the code.
Comment
The URI may be an OID (urn:oid:...) or a UUID (urn:uuid:...). OIDs and UUIDs SHALL be references to the HL7 OID registry. Otherwise, the URI should come from HL7's list of FHIR defined special URIs or it should de-reference to some definition that establish the system clearly and unambiguously.
Requirements
Need to be unambiguous about the source of the definition of the symbol.
Path
Reference.identifier.Identifier.type.CodeableConcept.coding.Coding.version
Id
Coding.version
Type
Cardinality
0 - 1
Definition
The version of the code system which was used when choosing this code. Note that a well-maintained code system does not need the version reported, because the meaning of codes is consistent across versions. However this cannot consistently be assured. and when the meaning is not guaranteed to be consistent, the version SHOULD be exchanged.
Comment
Where the terminology does not clearly define what string should be used to identify code system versions, the recommendation is to use the date (expressed in FHIR date format) on which that version was officially published as the version date.
Path
Reference.identifier.Identifier.type.CodeableConcept.coding.Coding.code
Id
Coding.code
Type
Cardinality
0 - 1
Definition
A symbol in syntax defined by the system. The symbol may be a predefined code or an expression in a syntax defined by the coding system (e.g. post-coordination).
Comment
Requirements
Need to refer to a particular code in the system.
Path
Reference.identifier.Identifier.type.CodeableConcept.coding.Coding.display
Id
Coding.display
Type
Cardinality
0 - 1
Definition
A representation of the meaning of the code in the system, following the rules of the system.
Comment
Requirements
Need to be able to carry a human-readable meaning of the code for readers that do not know the system.
Path
Reference.identifier.Identifier.type.CodeableConcept.coding.Coding.userSelected
Id
Coding.userSelected
Type
Cardinality
0 - 1
Definition
Indicates that this coding was chosen by a user directly - i.e. off a pick list of available items (codes or displays).
Comment
Amongst a set of alternatives, a directly chosen code is the most appropriate starting point for new translations. There is some ambiguity about what exactly 'directly chosen' implies, and trading partner agreement may be needed to clarify the use of this element and its consequences more completely.
Requirements
This has been identified as a clinical safety criterium - that this exact system/code pair was chosen explicitly, rather than inferred by the system based on some rules or language processing.
Path
Reference.identifier.Identifier.system
Id
Identifier.system
Type
Cardinality
0 - 1
Definition
Establishes the namespace for the value - that is, a URL that describes a set values that are unique.
Comment
Requirements
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.
Path
Reference.identifier.Identifier.value
Id
Identifier.value
Type
Cardinality
0 - 1
Definition
The portion of the identifier typically relevant to the user and which is unique within the context of the system.
Comment
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](extension-rendered-value.html).
Path
Reference.identifier.Identifier.period
Id
Identifier.period
Type
Cardinality
0 - 1
Definition
Time period during which identifier is/was valid for use.
Comment
Path
Reference.identifier.Identifier.period.Period.start
Id
Period.start
Type
Cardinality
0 - 1
Definition
The start of the period. The boundary is inclusive.
Comment
If the low element is missing, the meaning is that the low boundary is not known.
Condition
per-1
Path
Reference.identifier.Identifier.period.Period.end
Id
Period.end
Type
Cardinality
0 - 1
Definition
The end of the period. If the end of the period is missing, it means that the period is ongoing. The start may be in the past, and the end date in the future, which means that period is expected/planned to end at that time.
Comment
The high value includes any matching date/time. i.e. 2012-02-03T10:00:00 is in a period that has a end value of 2012-02-03.
Condition
per-1
Path
Reference.identifier.Identifier.assigner
Id
Identifier.assigner
Type
Cardinality
0 - 1
Definition
Organization that issued/manages the identifier.
Comment
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.
Path
Reference.identifier.Identifier.assigner.Reference.reference
Id
Reference.reference
Type
Cardinality
0 - 1
Definition
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.
Comment
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.
Condition
ref-1
Path
Reference.identifier.Identifier.assigner.Reference.identifier
Id
Reference.identifier
Type
Cardinality
0 - 1
Definition
An identifier for the other resource. This is used when there is no way to reference the other resource directly, either because the entity is not available through a FHIR server, or because there is no way for the author of the resource to convert a known identifier to an actual location. There is no requirement that a Reference.identifier point to something that is actually exposed as a FHIR instance, but it SHALL point to a business concept that would be expected to be exposed as a FHIR instance, and that instance would need to be of a FHIR resource type allowed by the reference.
Comment
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.
Path
Reference.identifier.Identifier.assigner.Reference.identifier.Identifier.use
Id
Identifier.use
Type
Cardinality
0 - 1
Definition
The purpose of this identifier.
Comment
This is labeled as "Is Modifier" because applications should not mistake a temporary id for a permanent one. Applications can assume that an identifier is permanent unless it explicitly says that it is temporary.
Requirements
Allows the appropriate identifier for a particular context of use to be selected from among a set of identifiers.
Path
Reference.identifier.Identifier.assigner.Reference.identifier.Identifier.type
Id
Identifier.type
Type
Cardinality
0 - 1
Definition
A coded type for the identifier that can be used to determine which identifier to use for a specific purpose.
Comment
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.
Requirements
Allows users to make use of identifiers when the identifier system is not known.
Path
Reference.identifier.Identifier.assigner.Reference.identifier.Identifier.system
Id
Identifier.system
Type
Cardinality
0 - 1
Definition
Establishes the namespace for the value - that is, a URL that describes a set values that are unique.
Comment
Requirements
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.
Path
Reference.identifier.Identifier.assigner.Reference.identifier.Identifier.value
Id
Identifier.value
Type
Cardinality
0 - 1
Definition
The portion of the identifier typically relevant to the user and which is unique within the context of the system.
Comment
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](extension-rendered-value.html).
Path
Reference.identifier.Identifier.assigner.Reference.identifier.Identifier.period
Id
Identifier.period
Type
Cardinality
0 - 1
Definition
Time period during which identifier is/was valid for use.
Comment
Path
Reference.identifier.Identifier.assigner.Reference.identifier.Identifier.assigner
Id
Identifier.assigner
Type
Cardinality
0 - 1
Definition
Organization that issued/manages the identifier.
Comment
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.
Path
Reference.identifier.Identifier.assigner.Reference.display
Id
Reference.display
Type
Cardinality
0 - 1
Definition
Plain text narrative that identifies the resource in addition to the resource reference.
Comment
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.
Path
Reference.display
Id
Reference.display
Type
Cardinality
0 - 1
Definition
Plain text narrative that identifies the resource in addition to the resource reference.
Comment
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.