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

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).

A human language.

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.

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.

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

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

CDA Document Id extension and root.

The purpose of this identifier.

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

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

Identifies the purpose for this identifier, if known .

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

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

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.

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

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

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").

Period is not used for a duration (a measure of elapsed time). See Duration.

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 underlying document.

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

Status of the underlying document.

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

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

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.

Indicates that this coding was chosen by a user directly - e.g. 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.

A human language representation of the concept as seen/selected/uttered by the user who entered the data and/or which represents the intended meaning of the user.

The codes from the terminologies do not always capture the correct meaning with all the nuances of the human using them, or sometimes there is no appropriate code at all. In these cases, the text is used to capture the full meaning of the source.

Very often the text is the same as a displayName of one of the codings.

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

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 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 SHALL NOT exceed 1MB in size

Indicates that this coding was chosen by a user directly - e.g. 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.

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 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 SHALL NOT exceed 1MB in size

Indicates that this coding was chosen by a user directly - e.g. 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.

A human language representation of the concept as seen/selected/uttered by the user who entered the data and/or which represents the intended meaning of the user.

The codes from the terminologies do not always capture the correct meaning with all the nuances of the human using them, or sometimes there is no appropriate code at all. In these cases, the text is used to capture the full meaning of the source.

Very often the text is the same as a displayName of one of the codings.

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

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.

Aa resource (or, for logical models, the URI of the logical model).

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

The purpose of this identifier.

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

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

Identifies the purpose for this identifier, if known .

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

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

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.

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

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

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").

Period is not used for a duration (a measure of elapsed time). See Duration.

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.

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

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.

Aa resource (or, for logical models, the URI of the logical model).

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

The purpose of this identifier.

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

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

Identifies the purpose for this identifier, if known .

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

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

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.

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

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

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").

Period is not used for a duration (a measure of elapsed time). See Duration.

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.

Which person or organization authenticates that this document is valid.

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

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

Identifies the logical organization (software system, vendor, or department) to go to find the current version, where to report issues, etc. This is different from the physical location (URL, disk drive, or server) of the document, which is the technical location of the document, which host may be delegated to the management of some other organization.

Human-readable description of the source document.

Helps humans to assess whether the document is of interest.

What the document is about, a terse summary of the document.

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

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

The confidentiality codes can carry multiple vocabulary items. HL7 has developed an understanding of security and privacy tags that might be desirable in a Document Sharing environment, called HL7 Healthcare Privacy and Security Classification System (HCS). The following specification is recommended but not mandated, as the vocabulary bindings are an administrative domain responsibility. The use of this method is up to the policy domain such as the XDS Affinity Domain or other Trust Domain where all parties including sender and recipients are trusted to appropriately tag and enforce.

In the HL7 Healthcare Privacy and Security Classification (HCS) there are code systems specific to Confidentiality, Sensitivity, Integrity, and Handling Caveats. Some values would come from a local vocabulary as they are related to workflow roles and special projects.

Security Labels from the Healthcare Privacy and Security Classification System.

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 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).

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.

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 location where the data can be accessed.

The data needs to be transmitted by reference.

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

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

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

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

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

Included so that applications can verify that the contents of a location have not changed due to technical failures (e.g., storage rot, transport glitch, incorrect version).

The hash is calculated on the data prior to base64 encoding, if the data is based64 encoded. The hash is not intended to support digital signatures. Where protection against malicious threats a digital signature should be considered, see Provenance.signature for mechanism to protect a resource with a digital signature.

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

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

Note that FHIR strings SHALL NOT exceed 1MB in size

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

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

Document Format Codes.

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 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).

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.

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.

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

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.

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

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

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

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

The kind of facility where the patient was seen.

Not all terminology uses fit this general pattern. In some cases, models should not use CodeableConcept and use Coding directly and provide their own structure for managing text, codings, translations and the relationship between elements and pre- and post-coordination.

XDS Facility Type.

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

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

This element should be based on a coarse classification system for the class of specialty practice. Recommend the use of the classification system for Practice Setting, such as that described by the Subject Matter Domain in LOINC.

Additional details about where the content was created (e.g. clinical specialty).