Sets minimum expectations for questionnaire support for SDC-conformant systems, regardless of which SDC capabilities they're making use of.

Information captured by the author/maintainer of the questionnaire for development purposes, not intended to be seen by users.

Allows capture of todos, rationale for design decisions, etc. It can also be used to capture comments about the completion of the form in general. Allows commentary to be captured during the process of answering a questionnaire (if not already supported by the form design) as well as after the form is completed. Comments are not part of the "data" of the form. If a form prompts for a comment, this should be captured in an answer, not in this element. Formal assessments of the QuestionnareResponse would use Observation.

Indicates the terminology server(s) that are known to be capable of returning and potentially expanding the value set(s) associated with the whole questionnaire or a particular group or question within the questionnaire (depending on where the extension appears). If a full URL is not provided AND the requested query is a terminology operation (e.g. $lookup or $expand) the client SHOULD execute the operation against the preferredTerminologyServer rather than the local repository.

This includes those referenced by answerValueSet as well as the unitValueSet extension.

Indicates the types of resources that can record answers to a Questionnaire. Open Issue: Should this extension be moved to core?

​If present, indicates that this questionnaire has expectations with respect to assembly. Specifically, indicates whether this form requires assembly (i.e. it can't be used directly without invoking the $assemble operation operation on it) and/or whether it is intended for use only as a 'child' in an assembly process. The assembly processs might mean filling in item metadata based on information looked up from item.definitions and/or retrieving sub-questionnaires pointed to by sub-questionnaire extensions.

SDC-conformant Questionnaires SHALL declare this extension if they require an assembly process prior to use. If not declared, then the Questionnaire is not necessarily safe for use as a child form and does not require assembly prior to use.

A Questionnaire SHOULD specify the subject. However, it is optional to support legacy questionnaires.

Information captured by the author/maintainer of the questionnaire for development purposes, not intended to be seen by users.

Allows capture of todos, rationale for design decisions, etc. It can also be used to capture comments about specific groups or questions within it. Allows commentary to be captured during the process of answering a questionnaire (if not already supported by the form design) as well as after the form is completed. Comments are not part of the "data" of the form. If a form prompts for a comment, this should be captured in an answer, not in this element. Formal assessments of the QuestionnareResponse would use Observation.

Indicates the terminology server(s) that are known to be capable of returning and potentially expanding the value set(s) associated with the whole questionnaire or a particular group or question within the questionnaire (depending on where the extension appears). If a full URL is not provided AND the requested query is a terminology operation (e.g. $lookup or $expand) the client SHOULD execute the operation against the preferredTerminologyServer rather than the local repository.

This includes those referenced by answerValueSet as well as the unitValueSet extension.

Time is handled using "string". File is handled using Attachment. (Content can be sent as a contained binary).

An indication, if true, that a QuestionnaireResponse for this item may include multiple answers associated with a single instance of this item (for question-type items) or multiple repetitions of the item (for group-type items)

Sets minimum expectations for questionnaire support for SDC-conformant systems, regardless of which SDC capabilities they're making use of.

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.

An Extension

• value @ url

Information captured by the author/maintainer of the questionnaire for development purposes, not intended to be seen by users.

Allows capture of todos, rationale for design decisions, etc. It can also be used to capture comments about the completion of the form in general. Allows commentary to be captured during the process of answering a questionnaire (if not already supported by the form design) as well as after the form is completed. Comments are not part of the "data" of the form. If a form prompts for a comment, this should be captured in an answer, not in this element. Formal assessments of the QuestionnareResponse would use Observation.

Indicates the terminology server(s) that are known to be capable of returning and potentially expanding the value set(s) associated with the whole questionnaire or a particular group or question within the questionnaire (depending on where the extension appears). If a full URL is not provided AND the requested query is a terminology operation (e.g. $lookup or $expand) the client SHOULD execute the operation against the preferredTerminologyServer rather than the local repository.

This includes those referenced by answerValueSet as well as the unitValueSet extension.

Indicates the types of resources that can record answers to a Questionnaire. Open Issue: Should this extension be moved to core?

​If present, indicates that this questionnaire has expectations with respect to assembly. Specifically, indicates whether this form requires assembly (i.e. it can't be used directly without invoking the $assemble operation operation on it) and/or whether it is intended for use only as a 'child' in an assembly process. The assembly processs might mean filling in item metadata based on information looked up from item.definitions and/or retrieving sub-questionnaires pointed to by sub-questionnaire extensions.

SDC-conformant Questionnaires SHALL declare this extension if they require an assembly process prior to use. If not declared, then the Questionnaire is not necessarily safe for use as a child form and does not require assembly prior to use.

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 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 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).

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.

An absolute URI that is used to identify this questionnaire when it is referenced in a specification, model, design or an instance; also called its canonical identifier. This SHOULD be globally unique and SHOULD be a literal address at which at which an authoritative instance of this questionnaire is (or will be) published. This URL can be the target of a canonical reference. It SHALL remain the same when the questionnaire is stored on different servers.

… This is the id that will be used to link a QuestionnaireResponse to the Questionnaire the response is for.

The name of the referenced questionnaire can be conveyed using the http://hl7.org/fhir/StructureDefinition/display extension.

A formal identifier that is used to identify this questionnaire when it is represented in other formats, or referenced in a specification, model, design or an instance.

Allows externally provided and/or usable business identifiers to be easily associated with the module.

Typically, this is used for identifiers that can go in an HL7 V3 II (instance identifier) data type, and can then identify this questionnaire outside of FHIR, where it is not possible to use the logical URI.

The identifier that is used to identify this version of the questionnaire when it is referenced in a specification, model, design or instance. This is an arbitrary value managed by the questionnaire 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 questionnaire instances that have the same identifier but different versions. The version can be appended to the url in a reference to allow a reference to a particular business version of the questionnaire with the format [url]|[version].

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

Support human navigation and code generation.

The name is not expected to be globally unique. The name should be a simple alphanumeric type name to ensure that it is machine-processing friendly.

A short, descriptive, user-friendly title for the questionnaire.

This name does not need to be machine-processing friendly and may contain punctuation, white-space, etc.

The URL of a Questionnaire that this Questionnaire is based on.

Allows a Questionnaire to be created based on another Questionnaire.

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

Allows filtering of questionnaires that are appropriate for use versus not.

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

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

Allows filtering of questionnaires that are appropriate for use versus not.

The types of subjects that can be the subject of responses created for the questionnaire.

A Questionnaire SHOULD specify the subject. However, it is optional to support legacy questionnaires.

If none are specified, then the subject is unlimited.

The date (and optionally time) when the questionnaire was published. The date must change 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 questionnaire changes.

Note that this is not the same as the resource last-modified-date, since the resource may be a secondary representation of the questionnaire. 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 organization or individual that published the questionnaire.

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

Usually an organization but may be an individual. The publisher (or steward) of the questionnaire is the organization or individual primarily responsible for the maintenance and upkeep of the questionnaire. 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 questionnaire. This item SHOULD be populated unless the information is available from context.

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.

A free text natural language description of the questionnaire from a consumer's perspective.

This description can be used to capture details such as why the questionnaire 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 questionnaire 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 questionnaire is presumed to be the predominant language in the place the questionnaire was created).

The content was developed with a focus and intent of supporting the contexts that are listed. These contexts may be general categories (gender, age, ...) or may be references to specific programs (insurance plans, studies, ...) and may be used to assist with indexing and searching for appropriate questionnaire instances.

Assist in searching for appropriate content.

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

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

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

Explanation of why this questionnaire is needed and why it has been designed as it has.

This element does not describe the usage of the questionnaire. 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 questionnaire.

A copyright statement relating to the questionnaire and/or its contents. Copyright statements are generally legal restrictions on the use and publishing of the questionnaire.

Consumers must be able to determine any legal restrictions on the use of the questionnaire and/or its content.

The date on which the resource content was approved by the publisher. Approval happens once when the content is officially approved for usage.

The 'date' element may be more recent than the approval date because of minor changes or editorial corrections.

The date on which the resource content was last reviewed. Review happens periodically after approval but does not change the original approval date.

Gives a sense of how "current" the content is. Resources that have not been reviewed in a long time may have a risk of being less appropriate/relevant.

If specified, this date follows the original approval date.

The period during which the questionnaire content was or is planned to be in active use.

Allows establishing a transition before a resource comes into effect and also allows for a sunsetting process when new versions of the questionnaire are or are expected to be used instead.

The effective period for a questionnaire determines when the content is applicable for usage and is independent of publication and review dates. For example, a measure intended to be used for the year 2016 might be published in 2015.

An identifier for this question or group of questions in a particular terminology such as LOINC.

Allows linking of the complete Questionnaire resources to formal terminologies. It's common for "panels" of questions to be identified by a code.

A particular question, question grouping or display text that is part of the questionnaire.

The content of the questionnaire is constructed from an ordered, hierarchical collection of items.

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

An Extension

• value @ url

Information captured by the author/maintainer of the questionnaire for development purposes, not intended to be seen by users.

Allows capture of todos, rationale for design decisions, etc. It can also be used to capture comments about specific groups or questions within it. Allows commentary to be captured during the process of answering a questionnaire (if not already supported by the form design) as well as after the form is completed. Comments are not part of the "data" of the form. If a form prompts for a comment, this should be captured in an answer, not in this element. Formal assessments of the QuestionnareResponse would use Observation.

Indicates the terminology server(s) that are known to be capable of returning and potentially expanding the value set(s) associated with the whole questionnaire or a particular group or question within the questionnaire (depending on where the extension appears). If a full URL is not provided AND the requested query is a terminology operation (e.g. $lookup or $expand) the client SHOULD execute the operation against the preferredTerminologyServer rather than the local repository.

This includes those referenced by answerValueSet as well as the unitValueSet extension.

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.

An identifier that is unique within the Questionnaire allowing linkage to the equivalent item in a QuestionnaireResponse resource.

QuestionnaireResponse does not require omitted items to be included and may have some items that repeat, so linkage based on position alone is not sufficient.

This ''can'' be a meaningful identifier (e.g. a LOINC code) but is not intended to have any meaning. GUIDs or sequential numbers are appropriate here.

This element is a URI that refers to an ElementDefinition that provides information about this item, including information that might otherwise be included in the instance of the Questionnaire resource. A detailed description of the construction of the URI is shown in Comments, below. If this element is present then the following element values MAY be derived from the Element Definition if the corresponding elements of this Questionnaire resource instance have no value:

• code (ElementDefinition.code)
• type (ElementDefinition.type)
• required (ElementDefinition.min)
• repeats (ElementDefinition.max)
• maxLength (ElementDefinition.maxLength)
• answerValueSet (ElementDefinition.binding)
• options (ElementDefinition.binding).

A common pattern is to define a set of data elements and then build multiple questionnaires for different circumstances to gather the data. This element provides traceability to the common definition and allows the content for the question to come from the underlying definition.

The uri refers to an ElementDefinition in a StructureDefinition and always starts with the canonical URL for the target resource. When referring to a StructureDefinition, a fragment identifier is used to specify the element definition by its id Element.id. E.g. http://hl7.org/fhir/StructureDefinition/Observation#Observation.value[x]. In the absence of a fragment identifier, the first/root element definition in the target is the matching element definition.

A terminology code that corresponds to this group or question (e.g. a code from LOINC, which defines many questions and answers).

Allows linking of groups of questions to formal terminologies.

The value may come from the ElementDefinition referred to by .definition.

A short label for a particular group, question or set of display text within the questionnaire used for reference by the individual completing the questionnaire.

Separating the label from the question text allows improved rendering. Also, instructions will often refer to specific prefixes, so there's a need for the questionnaire design to have control over what labels are used.

These are generally unique within a questionnaire, though this is not guaranteed. Some questionnaires may have multiple questions with the same label with logic to control which gets exposed. Typically, these won't be used for "display" items, though such use is not prohibited. Systems SHOULD NOT generate their own prefixes if prefixes are defined for any items within a Questionnaire.

The name of a section, the text of a question or text content for a display item.

When using this element to represent the name of a section, use group type item and also make sure to limit the text element to a short string suitable for display as a section heading. Group item instructions should be included as a display type item within the group.

The type of questionnaire item this is - whether text for display, a grouping of other items or a particular type of data to be captured (string, integer, coded choice, etc.).

Defines the format in which the user is to be prompted for the answer.

Time is handled using "string". File is handled using Attachment. (Content can be sent as a contained binary).

A constraint indicating that this item should only be enabled (displayed/allow answers to be captured) when the specified condition is true.

Allows questionnaires to adapt based on answers to other questions. E.g. If physical gender is specified as a male, no need to capture pregnancy history. Also allows conditional display of instructions or groups of questions.

If multiple repetitions of this extension are present, the item should be enabled when the condition for any of the repetitions is true. I.e. treat "enableWhen"s as being joined by an "or" clause. This element is a modifier because if enableWhen is present for an item, "required" is ignored unless one of the enableWhen conditions is met. When an item is disabled, all of its descendants are disabled, regardless of what their own enableWhen logic might evaluate to.

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 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.

The linkId for the question whose answer (or lack of answer) governs whether this item is enabled.

If multiple question occurrences are present for the same question (same linkId), then this refers to the nearest question occurrence reachable by tracing first the "ancestor" axis and then the "preceding" axis and then the "following" axis.

Specifies the criteria by which the question is enabled.

A value that the referenced question is tested using the specified operator in order for the item to be enabled.

Controls how multiple enableWhen values are interpreted - whether all or any must be true.

This element must be specified if more than one enableWhen value is provided.

An indication, if true, that the item must be present in a "completed" QuestionnaireResponse. If false, the item may be skipped when answering the questionnaire.

Questionnaire.item.required only has meaning for elements that are conditionally enabled with enableWhen if the condition evaluates to true. If an item that contains other items is marked as required, that does not automatically make the contained elements required (though required groups must contain at least one child element). The value may come from the ElementDefinition referred to by .definition.

An indication, if true, that a QuestionnaireResponse for this item may include multiple answers associated with a single instance of this item (for question-type items) or multiple repetitions of the item (for group-type items)

Items may be used to create set of (related) questions that can be repeated to give multiple answers to such a set.

If a question is marked as repeats=true, then multiple answers can be provided for the question in the corresponding QuestionnaireResponse. When rendering the questionnaire, it is up to the rendering software whether to render the question text for each answer repetition (i.e. "repeat the question") or to simply allow entry/selection of multiple answers for the question (repeat the answers). Which is most appropriate visually may depend on the type of answer as well as whether there are nested items.

The resulting QuestionnaireResponse will be populated the same way regardless of rendering - one 'question' item with multiple answer values.

The value may come from the ElementDefinition referred to by .definition.

An indication, when true, that the value cannot be changed by a human respondent to the Questionnaire.

Allows certain information to be phrased (and rendered) as a question and an answer, while keeping users from changing it. May also be useful for preventing changes to pre-populated portions of a questionnaire, for calculated values, etc.

The value of readOnly elements can be established by asserting extensions for defaultValues, linkages that support pre-population and/or extensions that support calculation based on other answers.

The maximum number of characters that are permitted in the answer to be considered a "valid" QuestionnaireResponse.

For base64binary, reflects the number of characters representing the encoded data, not the number of bytes of the binary data. The value may come from the ElementDefinition referred to by .definition.

A reference to a value set containing a list of codes representing permitted answers for a "choice" or "open-choice" question.

LOINC defines many useful value sets for questionnaire responses. See LOINC Answer Lists. The value may come from the ElementDefinition referred to by .definition.

One of the permitted answers for a "choice" or "open-choice" question.

This element can be used when the value set machinery of answerValueSet is deemed too cumbersome or when there's a need to capture possible answers that are not 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. 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 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 potential answer that's allowed as the answer to this question.

The data type of the value must agree with the item.type.

Indicates whether the answer value is selected when the list of possible answers is initially shown.

Use this instead of initial[v] if answerValueSet is present.

One or more values that should be pre-populated in the answer when initially rendering the questionnaire for user input.

In some workflows, having defaults saves time.

The user is allowed to change the value and override the default (unless marked as read-only). If the user doesn't change the value, then this initial value will be persisted when the QuestionnaireResponse is initially created. Note that initial values can influence results. The data type of initial[x] must agree with the item.type, and only repeating items can have more then one initial value.

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 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.

The actual value to for an initial answer.

The type of the initial value must be consistent with the type of the item.

Text, questions and other groups to be nested beneath a question or group.

Reports can consist of complex nested groups.

There is no specified limit to the depth of nesting. However, Questionnaire authors are encouraged to consider the impact on the user and user interface of overly deep nesting.