A search parameter that defines a named search item that can be used to search/filter on a resource.

In FHIR, search is not performed directly on a resource (by XML or JSON path), but on a named parameter that maps into the resource content.

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.

This element is labelled as a modifier because the implicit rules may provide additional knowledge about the resource that modifies it's meaning or interpretation.

An Extension

R4B: SearchParameter.multipleOr (new:boolean)

Element SearchParameter.multipleOr has a context of SearchParameter based on following the parent source element upwards and mapping to SearchParameter. Element SearchParameter.multipleOr has no mapping targets in FHIR STU3. Typically, this is because the element has been added (is a new element).

R4B: SearchParameter.multipleAnd (new:boolean)

Element SearchParameter.multipleAnd has a context of SearchParameter based on following the parent source element upwards and mapping to SearchParameter. Element SearchParameter.multipleAnd has no mapping targets in FHIR STU3. Typically, this is because the element has been added (is a new element).

May be used to represent additional information that is not part of the basic definition of the resource, and that modifies the understanding of the element that contains it. 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.

An absolute URI that is used to identify this search parameter when it is referenced in a specification, model, design or an instance. This SHALL be a URL, SHOULD be globally unique, and SHOULD be an address at which this search parameter is (or will be) published. The URL SHOULD include the major version of the search parameter. For more information see Technical and Business Versions.

Can be a urn:uuid: or a urn:oid:, but real http: addresses are preferred. Multiple instances may share the same url if they have a distinct version.

Allows the search parameter to be referenced by a single globally unique identifier. To allow referencing and reusing search parameter definitions under other names on operational systems (in case of name clash).

A natural language name identifying the search parameter. This name should be usable as an identifier for the module by machine processing applications such as code generation.

The name is not expected to be globally unique. The name should be a simple alpha-numeric type name to ensure that it is computable friendly.

Support human navigation and code generation.

The status of this search parameter. Enables tracking the life-cycle of the content.

Allows filtering of search parameters that are appropriate for use vs. not.
This is labeled as "Is Modifier" because applications should not use a retired search parameter without due consideration.

The lifecycle status of a Value Set or Concept Map.

A boolean value to indicate that this search parameter is authored for testing purposes (or education/evaluation/marketing), and is not intended to be used for genuine usage.

Allows filtering of search parameter that are appropriate for use vs. not. This is labeled as "Is Modifier" because applications should not use an experimental search parameter in production.

Enables experimental content to be developed following the same lifecycle that would be used for a production-level search parameter.

The code used in the URL or the parameter name in a parameters resource for this search parameter.

For maximum compatibility, use only lowercase ASCII characters.

The base resource type(s) that this search parameter can be used against.

A search parameter must always have at least one type. When search parameters have more than one resource, they can be used against any of the listed resource types, or in a cross-type search (see Cross Resource Search).

The codes SHALL be taken from ResourceType http://hl7.org/fhir/ValueSet/resource-types|3.0.2
(required to http://hl7.org/fhir/ValueSet/resource-types|3.0.2)

One of the resource types defined as part of FHIR.

An Extension

R4B: SearchParameter.base additional codes

Element SearchParameter.base is mapped to FHIR STU3 element SearchParameter.base as RelatedTo. The mappings for SearchParameter.base do not allow expression of the necessary codes, per the bindings on the source and target. A search parameter must always apply to at least one resource type. When search parameters apply to more than one resource type, they can be used against any of the listed resource types, or in a cross-type search (see Cross Resource Search).

The type of value a search parameter refers to, and how the content is interpreted.

Data types allowed to be used for search parameters.

An Extension

R4B: SearchParameter.type

Element SearchParameter.type is mapped to FHIR STU3 element SearchParameter.type as SourceIsBroaderThanTarget.

A free text natural language description of the search parameter from a consumer's perspective. and how it used.

This description can be used to capture details such as why the search parameter was built, comments about misuse, instructions for clinical use and interpretation, literature references, examples from the paper world, etc. It is not a rendering of the search parameter as conveyed in the 'text' field of the resource itself. This item SHOULD be populated unless the information is available from context (e.g. the language of the profile is presumed to be the predominant language in the place the profile was created).

R4B: SearchParameter.meta additional types (Meta) additional types from child elements (lastUpdated, profile, security, source, tag, versionId)

Element SearchParameter.meta is mapped to FHIR STU3 element SearchParameter.meta as SourceIsBroaderThanTarget. The mappings for SearchParameter.meta do not cover the following types: Meta. The mappings for SearchParameter.meta do not cover the following types based on type expansion: lastUpdated, profile, security, source, tag, versionId.

R4B: SearchParameter.text additional types (Narrative) additional types from child elements (div, status)

Element SearchParameter.text is mapped to FHIR STU3 element SearchParameter.text as SourceIsBroaderThanTarget. The mappings for SearchParameter.text do not cover the following types: Narrative. The mappings for SearchParameter.text do not cover the following types based on type expansion: div, status. Contained resources do not have narrative. Resources that are not contained SHOULD have a narrative. In some cases, a resource may only have text with little or no additional discrete data (as long as all minOccurs=1 elements are satisfied). This may be necessary for data from legacy systems where information is captured as a "text blob" or where text is additionally entered raw or narrated and encoded information is added later.

R4B: SearchParameter.multipleOr (new:boolean)

Element SearchParameter.multipleOr has a context of SearchParameter based on following the parent source element upwards and mapping to SearchParameter. Element SearchParameter.multipleOr has no mapping targets in FHIR STU3. Typically, this is because the element has been added (is a new element).

R4B: SearchParameter.multipleAnd (new:boolean)

Element SearchParameter.multipleAnd has a context of SearchParameter based on following the parent source element upwards and mapping to SearchParameter. Element SearchParameter.multipleAnd has no mapping targets in FHIR STU3. Typically, this is because the element has been added (is a new element).

R4B: SearchParameter.contact additional types (ContactDetail) additional types from child elements (name, telecom)

Element SearchParameter.contact is mapped to FHIR STU3 element SearchParameter.contact as SourceIsBroaderThanTarget. The mappings for SearchParameter.contact do not cover the following types: ContactDetail. The mappings for SearchParameter.contact do not cover the following types based on type expansion: name, telecom. May be a web site, an email address, a telephone number, etc.

R4B: SearchParameter.useContext additional types (UsageContext) additional types from child elements (code, value[x])

Element SearchParameter.useContext is mapped to FHIR STU3 element SearchParameter.useContext as SourceIsBroaderThanTarget. The mappings for SearchParameter.useContext do not cover the following types: UsageContext. The mappings for SearchParameter.useContext do not cover the following types based on type expansion: code, value[x]. When multiple useContexts are specified, there is no expectation that all or any of the contexts apply.

R4B: SearchParameter.base additional codes

Element SearchParameter.base is mapped to FHIR STU3 element SearchParameter.base as RelatedTo. The mappings for SearchParameter.base do not allow expression of the necessary codes, per the bindings on the source and target. A search parameter must always apply to at least one resource type. When search parameters apply to more than one resource type, they can be used against any of the listed resource types, or in a cross-type search (see Cross Resource Search).

R4B: SearchParameter.type

Element SearchParameter.type is mapped to FHIR STU3 element SearchParameter.type as SourceIsBroaderThanTarget.

R4B: SearchParameter.target additional codes

Element SearchParameter.target is mapped to FHIR STU3 element SearchParameter.target as RelatedTo. The mappings for SearchParameter.target do not allow expression of the necessary codes, per the bindings on the source and target.

R4B: SearchParameter.modifier

Element SearchParameter.modifier is mapped to FHIR STU3 element SearchParameter.modifier as SourceIsBroaderThanTarget.

R4B: SearchParameter.component.definition additional types (canonical(http://hl7.org/fhir/StructureDefinition/SearchParameter)) additional types from child elements (value)

Element SearchParameter.component.definition is mapped to FHIR STU3 element SearchParameter.component.definition as SourceIsBroaderThanTarget. The mappings for SearchParameter.component.definition do not cover the following types: canonical. The mappings for SearchParameter.component.definition do not cover the following types based on type expansion: value.

A search parameter that defines a named search item that can be used to search/filter on a resource.

In FHIR, search is not performed directly on a resource (by XML or JSON path), but on a named parameter that maps into the resource content.

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

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

An Extension

R4B: SearchParameter.meta additional types (Meta) additional types from child elements (lastUpdated, profile, security, source, tag, versionId)

Element SearchParameter.meta is mapped to FHIR STU3 element SearchParameter.meta as SourceIsBroaderThanTarget. The mappings for SearchParameter.meta do not cover the following types: Meta. The mappings for SearchParameter.meta do not cover the following types based on type expansion: lastUpdated, profile, security, source, tag, versionId.

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

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

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

This value is always populated except when the resource is first being created. The server / resource manager sets this value; what a client provides is irrelevant.

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

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

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

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

Security Labels from the Healthcare Privacy and Security Classification System.

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

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

Codes that represent various types of tags, commonly workflow-related; e.g. "Needs review by Dr. Jones"

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.

This element is labelled as a modifier because the implicit rules may provide additional knowledge about the resource that modifies it's meaning or interpretation.

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 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. In some cases, a resource may only have text with little or no additional discrete data (as long as all minOccurs=1 elements are satisfied). This may be necessary for data from legacy systems where information is captured as a "text blob" or where text is additionally entered raw or narrated and encoded in formation is added later.

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

An Extension

R4B: SearchParameter.text additional types (Narrative) additional types from child elements (div, status)

Element SearchParameter.text is mapped to FHIR STU3 element SearchParameter.text as SourceIsBroaderThanTarget. The mappings for SearchParameter.text do not cover the following types: Narrative. The mappings for SearchParameter.text do not cover the following types based on type expansion: div, status. Contained resources do not have narrative. Resources that are not contained SHOULD have a narrative. In some cases, a resource may only have text with little or no additional discrete data (as long as all minOccurs=1 elements are satisfied). This may be necessary for data from legacy systems where information is captured as a "text blob" or where text is additionally entered raw or narrated and encoded information is added later.

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

The status of a resource narrative

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

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

These resources do not have an independent existence apart from the resource that contains them - they cannot be identified independently, and nor can they have their own independent transaction scope.

This should never be done when the content can be identified properly, as once identification is lost, it is extremely difficult (and context dependent) to restore it again.

An Extension

R4B: SearchParameter.multipleOr (new:boolean)

Element SearchParameter.multipleOr has a context of SearchParameter based on following the parent source element upwards and mapping to SearchParameter. Element SearchParameter.multipleOr has no mapping targets in FHIR STU3. Typically, this is because the element has been added (is a new element).

R4B: SearchParameter.multipleAnd (new:boolean)

Element SearchParameter.multipleAnd has a context of SearchParameter based on following the parent source element upwards and mapping to SearchParameter. Element SearchParameter.multipleAnd has no mapping targets in FHIR STU3. Typically, this is because the element has been added (is a new element).

May be used to represent additional information that is not part of the basic definition of the resource, and that modifies the understanding of the element that contains it. 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.

An absolute URI that is used to identify this search parameter when it is referenced in a specification, model, design or an instance. This SHALL be a URL, SHOULD be globally unique, and SHOULD be an address at which this search parameter is (or will be) published. The URL SHOULD include the major version of the search parameter. For more information see Technical and Business Versions.

Can be a urn:uuid: or a urn:oid:, but real http: addresses are preferred. Multiple instances may share the same url if they have a distinct version.

Allows the search parameter to be referenced by a single globally unique identifier. To allow referencing and reusing search parameter definitions under other names on operational systems (in case of name clash).

The identifier that is used to identify this version of the search parameter when it is referenced in a specification, model, design or instance. This is an arbitrary value managed by the search parameter author and is not expected to be globally unique. For example, it might be a timestamp (e.g. yyyymmdd) if a managed version is not available. There is also no expectation that versions can be placed in a lexicographical sequence.

There may be different search parameter instances that have the same identifier but different versions. The version can be appended to the url in a reference to allow a refrence to a particular business version of the search parameter with the format [url]|[version].

A natural language name identifying the search parameter. This name should be usable as an identifier for the module by machine processing applications such as code generation.

The name is not expected to be globally unique. The name should be a simple alpha-numeric type name to ensure that it is computable friendly.

Support human navigation and code generation.

The status of this search parameter. Enables tracking the life-cycle of the content.

Allows filtering of search parameters that are appropriate for use vs. not.
This is labeled as "Is Modifier" because applications should not use a retired search parameter without due consideration.

The lifecycle status of a Value Set or Concept Map.

A boolean value to indicate that this search parameter is authored for testing purposes (or education/evaluation/marketing), and is not intended to be used for genuine usage.

Allows filtering of search parameter that are appropriate for use vs. not. This is labeled as "Is Modifier" because applications should not use an experimental search parameter in production.

Enables experimental content to be developed following the same lifecycle that would be used for a production-level search parameter.

The date (and optionally time) when the search parameter was published. The date must change if and when the business version changes and it must change if the status code changes. In addition, it should change when the substantive content of the search parameter changes.

Note that this is not the same as the resource last-modified-date, since the resource may be a secondary representation of the search parameter. Additional specific dates may be added as extensions or be found by consulting Provenances associated with past versions of the resource.

The name of the individual or organization that published the search parameter.

Usually an organization, but may be an individual. The publisher (or steward) of the search parameter is the organization or individual primarily responsible for the maintenance and upkeep of the search parameter. This is not necessarily the same individual or organization that developed and initially authored the content. The publisher is the primary point of contact for questions or issues with the search parameter. This item SHOULD be populated unless the information is available from context.

Helps establish the "authority/credibility" of the search parameter. May also allow for contact.

Contact details to assist a user in finding and communicating with the publisher.

May be a web site, an email address, a telephone number, etc.

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

An Extension

R4B: SearchParameter.contact additional types (ContactDetail) additional types from child elements (name, telecom)

Element SearchParameter.contact is mapped to FHIR STU3 element SearchParameter.contact as SourceIsBroaderThanTarget. The mappings for SearchParameter.contact do not cover the following types: ContactDetail. The mappings for SearchParameter.contact do not cover the following types based on type expansion: name, telecom. May be a web site, an email address, a telephone number, etc.

The name of an individual to contact.

If there is no named individual, the telecom information is for the organization as a whole.

The contact details for the individual (if a name was provided) or the organization.

The content was developed with a focus and intent of supporting the contexts that are listed. These terms may be used to assist with indexing and searching for appropriate search parameter instances.

When multiple useContexts are specified, there is no expectation whether all or any of the contexts apply.

Assist in searching for appropriate content.

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

An Extension

R4B: SearchParameter.useContext additional types (UsageContext) additional types from child elements (code, value[x])

Element SearchParameter.useContext is mapped to FHIR STU3 element SearchParameter.useContext as SourceIsBroaderThanTarget. The mappings for SearchParameter.useContext do not cover the following types: UsageContext. The mappings for SearchParameter.useContext do not cover the following types based on type expansion: code, value[x]. When multiple useContexts are specified, there is no expectation that all or any of the contexts apply.

A code that identifies the type of context being specified by this usage context.

A code that specifies a type of context being specified by a usage context

A value that defines the context specified in this context of use. The interpretation of the value is defined by the code.

A code that defines the specific value for the context being specified

A legal or geographic region in which the search parameter is intended to be used.

It may be possible for the search parameter to be used in jurisdictions other than those for which it was originally designed or intended.

Countries and regions within which this artifact is targeted for use

Explaination of why this search parameter is needed and why it has been designed as it has.

This element does not describe the usage of the search parameter Instead it provides traceability of ''why'' the resource is either needed or ''why'' it is defined as it is. This may be used to point to source materials or specifications that drove the structure of this search parameter.

The code used in the URL or the parameter name in a parameters resource for this search parameter.

For maximum compatibility, use only lowercase ASCII characters.

The base resource type(s) that this search parameter can be used against.

A search parameter must always have at least one type. When search parameters have more than one resource, they can be used against any of the listed resource types, or in a cross-type search (see Cross Resource Search).

The codes SHALL be taken from ResourceType
(required to http://hl7.org/fhir/ValueSet/resource-types|3.0.2)

One of the resource types defined as part of FHIR.

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

An Extension

R4B: SearchParameter.base additional codes

Element SearchParameter.base is mapped to FHIR STU3 element SearchParameter.base as RelatedTo. The mappings for SearchParameter.base do not allow expression of the necessary codes, per the bindings on the source and target. A search parameter must always apply to at least one resource type. When search parameters apply to more than one resource type, they can be used against any of the listed resource types, or in a cross-type search (see Cross Resource Search).

Primitive value for code

The type of value a search parameter refers to, and how the content is interpreted.

Data types allowed to be used for search parameters.

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

An Extension

R4B: SearchParameter.type

Element SearchParameter.type is mapped to FHIR STU3 element SearchParameter.type as SourceIsBroaderThanTarget.

Primitive value for code

Where this search parameter is originally defined. If a derivedFrom is provided, then the details in the search parameter must be consistent with the definition from which it is defined. I.e. the parameter should have the same meaning, and (usually) the functionality should be a proper subset of the underlying search parameter.

The intent of this is that a server can designate that it provides support for a search parameter defined in the specification itself (e.g. value-quantity, but detail how it is supported by the server.

A free text natural language description of the search parameter from a consumer's perspective. and how it used.

This description can be used to capture details such as why the search parameter was built, comments about misuse, instructions for clinical use and interpretation, literature references, examples from the paper world, etc. It is not a rendering of the search parameter as conveyed in the 'text' field of the resource itself. This item SHOULD be populated unless the information is available from context (e.g. the language of the profile is presumed to be the predominant language in the place the profile was created).

A FHIRPath expression that returns a set of elements for the search parameter.

Note that the elements returned by the expression are sometimes complex elements where logic is required to determine quite how to handle them; e.g. CodeableConcepts may contain text and/or multiple codings, where the codings themselves contain a code and a system. For composite search parameters, the outcome of the expression must a collection of base elements from which the composites are derived.

An XPath expression that returns a set of elements for the search parameter.

Note that the elements returned by the XPath are sometimes complex elements where logic is required to determine quite how to handle them; e.g. CodeableConcepts may contain text and/or multiple codings, where the codings themselves contain a code and a system.

How the search parameter relates to the set of elements returned by evaluating the xpath query.

How a search parameter relates to the set of elements returned by evaluating its xpath query.

Types of resource (if a resource is referenced).

The codes SHALL be taken from ResourceType
(required to http://hl7.org/fhir/ValueSet/resource-types|3.0.2)

One of the resource types defined as part of FHIR.

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

An Extension

R4B: SearchParameter.target additional codes

Element SearchParameter.target is mapped to FHIR STU3 element SearchParameter.target as RelatedTo. The mappings for SearchParameter.target do not allow expression of the necessary codes, per the bindings on the source and target.

Primitive value for code

Comparators supported for the search parameter.

If no comparators are listed, clients should not expect servers to support any comparators.

What Search Comparator Codes are supported in search

A modifier supported for the search parameter.

A supported modifier for a search parameter.

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

An Extension

R4B: SearchParameter.modifier

Element SearchParameter.modifier is mapped to FHIR STU3 element SearchParameter.modifier as SourceIsBroaderThanTarget.

Primitive value for code

Contains the names of any search parameters which may be chained to the containing search parameter. Chained parameters may be added to search parameters of type reference, and specify that resources will only be returned if they contain a reference to a resource which matches the chained parameter value. Values for this field should be drawn from SearchParameter.code for a parameter on the target resource type.

Systems are not required to list all the chain names they support, but if they don't list them, clients may not know to use them.

Used to define the parts of a composite search parameter.

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. 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 definition of the search parameter that describes this part.

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

An Extension

R4B: SearchParameter.component.definition additional types (canonical(http://hl7.org/fhir/StructureDefinition/SearchParameter)) additional types from child elements (value)

Element SearchParameter.component.definition is mapped to FHIR STU3 element SearchParameter.component.definition as SourceIsBroaderThanTarget. The mappings for SearchParameter.component.definition do not cover the following types: canonical. The mappings for SearchParameter.component.definition do not cover the following types based on type expansion: value.

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.

An identifier for the other resource. This is used when there is no way to reference the other resource directly, either because the entity is not available through a FHIR server, or because there is no way for the author of the resource to convert a known identifier to an actual location. There is no requirement that a Reference.identifier point to something that is actually exposed as a FHIR instance, but it SHALL point to a business concept that would be expected to be exposed as a FHIR instance, and that instance would need to be of a FHIR resource type allowed by the reference.

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.

Plain text narrative that identifies the resource in addition to the resource reference.

This is generally not the same as the Resource.text of the referenced resource. The purpose is to identify what's being referenced, not to fully describe it.

A sub-expression that defines how to extract values for this component from the output of the main SearchParameter.expression.

This expression overrides the expression in the definition, and extracts the index values from the outcome of the composite expression.