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. Bundles always have an id, though it is usually a generated UUID.

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

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

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

The base language in which the resource is written.

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

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

Contained resources do not have narrative. Resources that are not contained SHOULD have a narrative.

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

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

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

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

The time that the message was sent.

Allows limited detection of out-of-order and delayed transmission. Also supports audit.

Note: This is intended for precisely observed times, typically system logs etc., and not human-reported times - for them, see date and dateTime below. Time zone is always required

Code that identifies the event this message represents and connects it with its definition. Events defined as part of the FHIR specification have the system value "http://hl7.org/fhir/message-events".

Drives the behavior associated with this message.

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.

unique id for the element within a resource (for internal references).

RFC 4122

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

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

The identification of the code system that defines the meaning of the symbol in the code.

Need to be unambiguous about the source of the definition of the symbol.

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.

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.

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.

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).

Need to refer to a particular code in the system.

Note that FHIR strings may not exceed 1MB in size

A representation of the meaning of the code in the system, following the rules of the system.

Need to be able to carry a human-readable meaning of the code for readers that do not know the system.

Note that FHIR strings may not exceed 1MB in size

Indicates that this coding was chosen by a user directly - i.e. off a pick list of available items (codes or displays).

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.

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.

Information about the message that this message is a response to. Only present if this message is a response.

unique id for the element within a resource (for internal references).

RFC 4122

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

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

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

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

The id of the message that this message is a response to.

Allows receiver to know what message is being responded to.

RFC 4122

Code that identifies the type of response to the message - whether it was successful or not, and whether it should be resent or not.

Allows the sender of the acknowledge message to know if the request was successful or if action is needed.

This is a generic response to the request message. Specific data for the response will be found in MessageHeader.data.

Full details of any issues found in the message.

Allows the sender of the message to determine what the specific issues are.

This SHALL be contained in the bundle. If any of the issues are errors, the response code SHALL be an error.

unique id for the element within a resource (for internal references).

RFC 4122

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

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

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.

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 source application from which this message originated.

Allows replies, supports audit.

unique id for the element within a resource (for internal references).

RFC 4122

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

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

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

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

Human-readable name for the source system.

May be used to support audit.

Note that FHIR strings may not exceed 1MB in size

May include configuration or other information useful in debugging.

Supports audit and possibly interface engine behavior.

Note that FHIR strings may not exceed 1MB in size

Can convey versions of multiple systems in situations where a message passes through multiple hands.

Supports audit and possibly interface engine behavior.

Note that FHIR strings may not exceed 1MB in size

An e-mail, phone, website or other contact point to use to resolve issues with message communications.

Allows escalation of technical issues.

unique id for the element within a resource (for internal references).

RFC 4122

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

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

Telecommunications form for contact point - what communications system is required to make use of the contact.

Note that FHIR strings may not exceed 1MB in size

The actual contact point details, in a form that is meaningful to the designated communication system (i.e. phone number or email address).

Need to support legacy numbers that are not in a tightly controlled format.

Additional text data such as phone extension numbers, or notes about use of the contact are sometimes included in the value.

Identifies the purpose for the contact point.

Need to track the way a person uses this contact, so a user can choose which is appropriate for their purpose.

This is labeled as "Is Modifier" because applications should not mistake a temporary or old contact etc.for a current/permanent one. Applications can assume that a contact is current unless it explicitly says that it is temporary or old.

Specifies a preferred order in which to use a set of contacts. Contacts are ranked with lower values coming before higher values.

Note that rank does not necessarily follow the order in which the contacts are represented in the instance.

Time period when the contact point was/is in use.

This is not a duration - that's a measure of time (a separate type), but a duration that occurs at a fixed value of time. A Period specifies a range of time; the context of use will specify whether the entire range applies (e.g. "the patient was an inpatient of the hospital for this time range") or one value from the range applies (e.g. "give to the patient between these two times"). If duration is required, specify the type as Interval|Duration.

unique id for the element within a resource (for internal references).

RFC 4122

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

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

The start of the period. The boundary is inclusive.

If the low element is missing, the meaning is that the low boundary is not known.

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.

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.

Identifies the routing target to send acknowledgements to.

Identifies where to send responses, may influence security permissions.

The id may be a non-resolvable URI for systems that do not use standard network-based addresses.

The destination application which the message is intended for.

Indicates where message is to be sent for routing purposes. Allows verification of "am I the intended recipient".

There SHOULD be at least one destination, but in some circumstances, the source system is unaware of any particular destination system.

unique id for the element within a resource (for internal references).

RFC 4122

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

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

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

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

Human-readable name for the target system.

May be used for routing of response and/or to support audit.

Note that FHIR strings may not exceed 1MB in size

Identifies the target end system in situations where the initial message transmission is to an intermediary system.

Supports multi-hop routing.

unique id for the element within a resource (for internal references).

RFC 4122

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

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

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.

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.

Indicates where the message should be routed to.

Identifies where to route the message.

The id may be a non-resolvable URI for systems that do not use standard network-based addresses.

The logical author of the message - the person or device that decided the described event should happen. Where there is more than one candidate, pick the most proximal to the MessageHeader. Can provide other authors in extensions.

Need to know for audit/traceback requirements and possibly for authorization.

Usually only for the request, but can be used in a response.

unique id for the element within a resource (for internal references).

RFC 4122

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

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

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.

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.

Allows data conveyed by a message to be addressed to a particular person or department when routing to a specific application isn't sufficient.

• Practitioner
• Organization

Allows routing beyond just the application level.