Demographics and other administrative information about an individual or animal receiving care or other health-related services.

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.

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-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.

May be used to represent additional information that is not part of the basic definition of the resource. 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.

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. 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.

An identifier for this patient.

Patients are almost always assigned specific numerical identifiers.

Whether this patient record is in active use. Many systems use this property to mark as non-current patients, such as those that have not been seen for a period of time based on an organization's business rules.

It is often used to filter patient lists to exclude inactive patients

Deceased patients may also be marked as inactive for the same reasons, but may be active for some time after death.

Need to be able to mark a patient record as not to be used because it was created in error.

If a record is inactive, and linked to an active record, then future patient/record updates should occur on the other patient.

A name associated with the individual.

Need to be able to track the patient by multiple names. Examples are your official name and a partner name. The Alphabetic representation of the name SHALL be always provided

A patient may have multiple names with different uses or applicable periods. For animals, the name is a "HumanName" in the sense that is assigned and used by humans and has the same patterns.

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.

Identifies the purpose for this name.

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

Applications can assume that a name is current unless it explicitly says that it is temporary or old.

Specifies the entire name as it should be displayed e.g. on an application UI. This may be provided instead of or as well as the specific parts.

A renderable, unencoded form.

Can provide both a text representation and parts. Applications updating a name SHALL ensure that when both text and parts are present, no content is included in the text that isn't found in a part.

The part of a name that links to the genealogy. In some cultures (e.g. Eritrea) the family name of a son is the first name of his father.

Family Name may be decomposed into specific parts using extensions (de, nl, es related cultures).

Given name.

If only initials are recorded, they may be used in place of the full name parts. Initials may be separated into multiple given names but often aren't due to paractical limitations. This element is not called "first name" since given names do not always come first.

Part of the name that is acquired as a title due to academic, legal, employment or nobility status, etc. and that appears at the start of the name.

Part of the name that is acquired as a title due to academic, legal, employment or nobility status, etc. and that appears at the end of the name.

Indicates the period of time when this name was valid for the named person.

Allows names to be placed in historical context.

A contact detail (e.g. a telephone number or an email address) by which the individual may be contacted.

People have (primary) ways to contact them in some way such as phone, email.

A Patient may have multiple ways to be contacted with different uses or applicable periods. May need to have options for contacting the person urgently and also to help with identification. The address might not go directly to the individual, but may reach another party that is able to proxy for the patient (i.e. home phone, or pet owner's phone).

Administrative Gender - the gender that the patient is considered to have for administration and record keeping purposes.

Needed for identification of the individual, in combination with (at least) name and birth date.

The gender might not match the biological sex as determined by genetics or the individual's preferred identification. Note that for both humans and particularly animals, there are other legitimate possibilities than male and female, though the vast majority of systems and contexts only support male and female. Systems providing decision support or enforcing business rules should ideally do this on the basis of Observations dealing with the specific sex or gender aspect of interest (anatomical, chromosomal, social, etc.) However, because these observations are infrequently recorded, defaulting to the administrative gender is common practice. Where such defaulting occurs, rule enforcement should allow for the variation between administrative and biological, chromosomal and other gender aspects. For example, an alert about a hysterectomy on a male should be handled as a warning or overridable error, not a "hard" error. See the Patient Gender and Sex section for additional information about communicating patient gender and sex.

The date of birth for the individual.

Age of the individual drives many clinical processes.

At least an estimated year should be provided as a guess if the real DOB is unknown There is a standard extension "patient-birthTime" available that should be used where Time is required (such as in maternity/infant care systems).

Indicates if the individual is deceased or not.

The fact that a patient is deceased influences the clinical process. Also, in human communication and relation management it is necessary to know whether the person is alive.

If there's no value in the instance, it means there is no statement on whether or not the individual is deceased. Most systems will interpret the absence of a value as a sign of the person being alive.

An address for the individual.

May need to keep track of patient addresses for contacting, billing or reporting requirements and also to help with identification.

Patient may have multiple addresses with different uses or applicable periods.

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.

The purpose of this address.

Allows an appropriate address to be chosen from a list of many.

Applications can assume that an address is current unless it explicitly says that it is temporary or old.

Distinguishes between physical addresses (those you can visit) and mailing addresses (e.g. PO Boxes and care-of addresses). Most addresses are both.

The definition of Address states that "address is for postal addresses, not physical locations". However, many applications track whether an address has a dual purpose of being a location that can be visited as well as being a valid delivery destination.

Specifies the entire address as it should be displayed e.g. on a postal label. This may be provided instead of or as well as the specific parts.

A renderable, unencoded form.

Can provide both a text representation and parts. Applications updating an address SHALL ensure that when both text and parts are present, no content is included in the text that isn't found in a part.

This component contains the house number, apartment number, street name, street direction, P.O. Box number, delivery hints, and similar address information.

The name of the city, town, suburb, village or other community or delivery center.

The name of the administrative area (county).

District is sometimes known as county, but in some regions 'county' is used in place of city (municipality), so county name should be conveyed in city instead.

Sub-unit of a country with limited sovereignty in a federally organized country. A code may be used if codes are in common use (e.g. US 2 letter state codes).

A postal code designating a region defined by the postal service.

Country - a nation as commonly understood or generally accepted.

ISO 3166 3 letter codes can be used in place of a full country name.

Required for cross-border exchange of IPS

Time period when address was/is in use.

Allows addresses to be placed in historical context.

This field contains a patient's most recent marital (civil) status.

Most, if not all systems capture it.

Indicates whether the patient is part of a multiple (boolean) or indicates the actual birth order (integer).

For disambiguation of multiple-birth children, especially relevant where the care provider doesn't meet the patient, such as labs.

Where the valueInteger is provided, the number is the birth number in the sequence. E.g. The middle birth in triplets would be valueInteger=2 and the third born would have valueInteger=3 If a boolean value was provided for this triplets example, then all 3 patient records would have valueBoolean=true (the ordering is not indicated).

Image of the patient.

Many EHR systems have the capability to capture an image of the patient. Fits with newer social media usage too.

Guidelines:

• Use id photos, not clinical photos.
• Limit dimensions to thumbnail.
• Keep byte count low to ease resource updates.

A contact party (e.g. guardian, partner, friend) for the patient.

Need to track people you can contact about the patient.

Contact covers all kinds of contact parties: family members, business contacts, guardians, caregivers. Not applicable to register pedigree and family ties beyond use of having contact.

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.

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. 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.

The nature of the relationship between the patient and the contact person.

Used to determine which contact person is the most relevant to approach, depending on circumstances.

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.

A name associated with the contact person.

Contact persons need to be identified by name, but it is uncommon to need details about multiple other names for that contact person.

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.

Identifies the purpose for this name.

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

Applications can assume that a name is current unless it explicitly says that it is temporary or old.

Specifies the entire name as it should be displayed e.g. on an application UI. This may be provided instead of or as well as the specific parts.

A renderable, unencoded form.

Can provide both a text representation and parts. Applications updating a name SHALL ensure that when both text and parts are present, no content is included in the text that isn't found in a part.

The part of a name that links to the genealogy. In some cultures (e.g. Eritrea) the family name of a son is the first name of his father.

Family Name may be decomposed into specific parts using extensions (de, nl, es related cultures).

Given name.

If only initials are recorded, they may be used in place of the full name parts. Initials may be separated into multiple given names but often aren't due to paractical limitations. This element is not called "first name" since given names do not always come first.

Part of the name that is acquired as a title due to academic, legal, employment or nobility status, etc. and that appears at the start of the name.

Part of the name that is acquired as a title due to academic, legal, employment or nobility status, etc. and that appears at the end of the name.

Indicates the period of time when this name was valid for the named person.

Allows names to be placed in historical context.

A contact detail for the person, e.g. a telephone number or an email address.

People have (primary) ways to contact them in some way such as phone, email.

Contact may have multiple ways to be contacted with different uses or applicable periods. May need to have options for contacting the person urgently, and also to help with identification.

Address for the contact person.

Need to keep track where the contact person can be contacted per postal mail or visited.

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.

The purpose of this address.

Allows an appropriate address to be chosen from a list of many.

Applications can assume that an address is current unless it explicitly says that it is temporary or old.

Distinguishes between physical addresses (those you can visit) and mailing addresses (e.g. PO Boxes and care-of addresses). Most addresses are both.

The definition of Address states that "address is for postal addresses, not physical locations". However, many applications track whether an address has a dual purpose of being a location that can be visited as well as being a valid delivery destination.

Specifies the entire address as it should be displayed e.g. on a postal label. This may be provided instead of or as well as the specific parts.

A renderable, unencoded form.

Can provide both a text representation and parts. Applications updating an address SHALL ensure that when both text and parts are present, no content is included in the text that isn't found in a part.

This component contains the house number, apartment number, street name, street direction, P.O. Box number, delivery hints, and similar address information.

The name of the city, town, suburb, village or other community or delivery center.

The name of the administrative area (county).

District is sometimes known as county, but in some regions 'county' is used in place of city (municipality), so county name should be conveyed in city instead.

Sub-unit of a country with limited sovereignty in a federally organized country. A code may be used if codes are in common use (e.g. US 2 letter state codes).

A postal code designating a region defined by the postal service.

Country - a nation as commonly understood or generally accepted.

ISO 3166 3 letter codes can be used in place of a human readable country name.

Time period when address was/is in use.

Allows addresses to be placed in historical context.

Administrative Gender - the gender that the contact person is considered to have for administration and record keeping purposes.

Needed to address the person correctly.

Organization on behalf of which the contact is acting or for which the contact is working.

For guardians or business related contacts, the organization is relevant.

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.

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 period during which this contact person or organization is valid to be contacted relating to this patient.

A language which may be used to communicate with the patient about his or her health.

If a patient does not speak the local language, interpreters may be required, so languages spoken and proficiency is an important things to keep track of both for patient and other persons of interest.

If no language is specified, this implies that the default local language is spoken. If you need to convey proficiency for multiple modes, then you need multiple Patient.Communication associations. For animals, language is not a relevant field, and should be absent from the instance. If the Patient does not speak the default local language, then the Interpreter Required Standard can be used to explicitly declare that an interpreter is required.

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.

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. 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.

The ISO-639-1 alpha 2 code in lower case for the language, optionally followed by a hyphen and the ISO-3166-1 alpha 2 code for the region in upper case; e.g. "en" for English, or "en-US" for American English versus "en-EN" for England English.

Most systems in multilingual countries will want to convey language. Not all systems actually need the regional dialect.

The structure aa-BB with this exact casing is one the most widely used notations for locale. However not all systems actually code this but instead have it as free text. Hence CodeableConcept instead of code as the data type.

Indicates whether or not the patient prefers this language (over other languages he masters up a certain level).

People that master multiple languages up to certain level may prefer one or more, i.e. feel more confident in communicating in a particular language making other languages sort of a fall back method.

This language is specifically identified for communicating healthcare information.

Patient's nominated care provider.

This may be the primary care provider (in a GP context), or it may be a patient nominated care manager in a community/disability setting, or even organization that will provide people to perform the care provider roles. It is not to be used to record Care Teams, these should be in a CareTeam resource that may be linked to the CarePlan or EpisodeOfCare resources. Multiple GPs may be recorded against the patient for various reasons, such as a student that has his home GP listed along with the GP at university during the school semesters, or a "fly-in/fly-out" worker that has the onsite GP also included with his home GP to remain aware of medical issues.

Jurisdictions may decide that they can profile this down to 1 if desired, or 1 per type.

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.

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.

Organization that is the custodian of the patient record.

Need to know who recognizes this patient record, manages and updates it.

There is only one managing organization for a specific patient record. Other organizations will have their own Patient record, and may use the Link property to join the records together (or a Person resource which can include confidence ratings for the association).

Link to another patient resource that concerns the same actual patient.

There are multiple use cases:

• Duplicate patient records due to the clerical errors associated with the difficulties of identifying humans consistently, and
• Distribution of patient information across multiple servers.

There is no assumption that linked patient records have mutual links.

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.

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. 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.

The other patient resource that the link refers to.

Referencing a RelatedPerson here removes the need to use a Person record to associate a Patient and RelatedPerson as the same individual.

The type of link between this patient resource and another patient resource.