Defines additional capabilities for controlling data entry and calculating values within the questionnaire.

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.

Optional Extension Element - found in all resources.

Optional Extension Element - found in all resources.

Indicates how questions within the questionnaire should be presented to the end-user. Specifically, differentiates whether the questions should be displayed one-at-a-time with no ability to adjust prior entries; one-at-a-time or continuously expanding where all questions up to the current question can be looked at and edited, or random, where all questions can be seen and the questions can be filled out in any order desired.

The prior-edit functionality can be accomplished by adding questions to the screen as each subsequent question is answered (resulting in all questions being displayed in a single screen) or with a view that shows only one question at a time but allows backward navigation to view and/or edit prior answers.

The base URL for the server to which questionnaire response associated with this questionnaire should be submitted. If multiple repetitions are present, the completed form should be sent to all listed endpoints.

Indicates that the form has been designed with an expectation that it will be submitted to the specified URI. If multiple endpoints are specified, expectation is that answers are submitted to all endpoints.

If no end-point is specified, then the form is not exclusively designed to be submitted to a specific site. If and where the form needs to be submitted or how the form should be internally processed must be inferred from external context or system business rules.

Endpoints may have expectations around authorization, etc. Some of this may be learned by consulting the CapabilityStatement associated with the endpoint.

Indicates that a signature (of the specified type) is needed when completing the QuestionnaireResponse.

If this appears at the Questionnaire level, then the signature will be gathered for the entire form when it is marked complete. If it appears on a particular item, then it will be gathered on that question or group when it is filled in. (E.g. seeking the user's initials beside certain questions.)

​The signature can be captured using the http://hl7.org/fhir/StructureDefinition/questionnaireresponse-signature extension. See additional guidance and examples in the SDC implementation guide.

Specifies a constraint that is enforced on instantiated (or target) resources. This extension can be applied to definitional resources (such as ActivityDefinition or Measure) and indicates that the constraint should be enforced on resources that are instantiated from the definition.

Can be used on any definitional artifact to define a constraint that is enforced in the context of an instantiated resource. The constraint expression will have access to %target and %definition variables, where target is the instantiated resource, and definition is the definition used to instantiate.

A reference to a library containing cql used in this Questionnaire.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

Resources that provide context for form processing logic (pre-population, flow-control, drop-down selection, etc.) when creating/displaying/editing a QuestionnaireResponse.

3 of these launch contexts are aligned with the existing SMART on FHIR "launch" contexts.

Variable specifying a logic to generate a variable for use in subsequent logic. The name of the variable will be added to FHIRPath's context when processing descendants of the element that contains this extension as well as extensions within the same element.

Ordering of variable extension declarations is significant as variables declared in one repetition of this extension might be used in subsequent extension repetitions

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

Allows variables to be calculated higher in the context of a QuestionnaireResponse for use with enableWhen-expression.

An Extension

Indicates an extension that must be supported by the system presenting the instance for data capture or end-user consumption. If a system does not recognize the extension or cannot implement the functionality defined by the extension, it should display an error message or warning and refrain from presenting the instance to the user or using it when capturing data.

This may point to extensions that control the appearance of data elements, control what value elements have, what elements are or are not available, what elements can or cannot be edited, or rules about how editing may occur. This extension does NOT apply when simply rendering a resource for publication purposes or for other purposes not intended for end-user data capture or data consumption.

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

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

The lifecycle status of an artifact.

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.

If true, indicates that the extended item should not be displayed to the user.

​If an item is hidden, all descendant items are hidden as well. See additional guidance and examples in the SDC implementation guide.

Optional Extension Element - found in all resources.

Optional Extension Element - found in all resources.

An expression (FHIRPath, CQL or FHIR Query) that resolves to a list of permitted answers for the question item or that establishes context for a group item. The user may select from among the list to choose answers for the question.

This is only permitted when the containing item does NOT have any answerOption or answerValueSet elements. The results of the expression must correspond to the item type of the question the element appears on or must correspond to a resource, backbone element or complex data type for a group item. Resources are considered a match for the Reference item type. Quantity can be a match for decimal and integer items so long as a questionnaire-unit extension is present. If the result of an expression returns a code or codes, it SHALL return the results as Coding, not code or CodeableConcept.

Identifies that the specified element should only appear in certain "modes" of operation.

​See additional guidance and examples in the SDC implementation guide.

Indicates that a signature (of the specified type) is needed when completing the QuestionnaireResponse.

If this appears at the Questionnaire level, then the signature will be gathered for the entire form when it is marked complete. If it appears on a particular item, then it will be gathered on that question or group when it is filled in. (E.g. seeking the user's initials beside certain questions.)

​The signature can be captured using the http://hl7.org/fhir/StructureDefinition/questionnaireresponse-signature extension. See additional guidance and examples in the SDC implementation guide.

The minimum number of times the group must appear, or the minimum number of answers for a question - when greater than 1.

​Default assumption for "required" elements is minOccurs=1. See additional guidance and examples in the SDC implementation guide.

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

An Extension

An expression that, when evaluated, provides the value for the element on which it appears.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

The maximum number of times the group must appear, or the maximum number of answers for a question - when greater than 1 and not unlimited.

​Only relevant if the element has repeats=true and there's a need to constrain the number of allowed repetitions. See additional guidance and examples in the SDC implementation guide.

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

An Extension

An expression that, when evaluated, provides the value for the element on which it appears.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

The minimum number of characters that must be present in the simple data type to be considered a "valid" instance.

​For base64binary, reflects the number of characters representing the encoded data, not the number of bytes of the binary data. For questionnaires, see additional guidance and examples in the SDC implementation guide.

A regular expression that defines the syntax for the data element to be considered valid.

The inclusive lower bound on the range of allowed values for the data element.

​Data type specified must be the same as the data type for the data element. For questionnaires, see additional guidance and examples in the SDC implementation guide.

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

An expression that determines a calculated value. The expression may be simply the name of a expression in a referenced library, or it may be a complete inline expression.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

The inclusive upper bound on the range of allowed values for the data element.

​Data type specified must be the same as the data type for the data element. For questionnaires, see additional guidance and examples in the SDC implementation guide.

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

An expression that determines a calculated value. The expression may be simply the name of a expression in a referenced library, or it may be a complete inline expression.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

The inclusive lower bound on the range of allowed values for a 'quantity' type question. Open Issue: Revisit whether this should be folded into the regular minValue extension once there are better capabilities around defining conformance expectations regarding extensions.

This must only be used if the set of permitted units is constrained to UCUM codes and the minimum checks will be performed by converting the answer.valueQuantity to the same units as the minQuantity unit prior to comparison.

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

An expression that determines a calculated value. The expression may be simply the name of a expression in a referenced library, or it may be a complete inline expression.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

How the value should be understood and represented - whether the actual value is greater or less than the stated value due to measurement issues; e.g. if the comparator is "<" , then the real value is < stated value.

How the Quantity should be understood and represented.

Need a framework for handling measures where the value is <5ug/L or >400mg/L due to the limitations of measuring methodology.

The inclusive upper bound on the range of allowed values for a 'quantity' type question. Open Issue: Revisit whether this should be folded into the regular maxValue extension once there are better capabilities around defining conformance expectations regarding extensions.

This must only be used if the set of permitted units is constrained to UCUM codes and the maximum checks will be performed by converting the answer.valueQuantity to the same units as the maxQuantity unit prior to comparison.

An Extension

Source of the definition for the extension code - a logical name or a URL.

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Value of extension - must be one of a constrained set of the data types (see Extensibility for a list).

An expression that determines a calculated value. The expression may be simply the name of a expression in a referenced library, or it may be a complete inline expression.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

How the value should be understood and represented - whether the actual value is greater or less than the stated value due to measurement issues; e.g. if the comparator is "<" , then the real value is < stated value.

How the Quantity should be understood and represented.

Need a framework for handling measures where the value is <5ug/L or >400mg/L due to the limitations of measuring methodology.

Identifies the maximum number of decimal places that may be specified for the data element.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

Identifies the kind(s) of attachment allowed to be sent for an element.

​This extension only has meaning if the element has a type of Attachment. For questionnaires, see additional guidance and examples in the SDC implementation guide.

For attachment answers, indicates the maximum size in bytes an attachment can be.

​This extension only has meaning if the element has a type of Attachment. For questionnaires, see additional guidance and examples in the SDC implementation guide.

A complex expression that provides a list of the allowed options that should be enabled or disabled based on the evaluation of a provided expression. It allows toggling of allowed answers based on context, including the answers provided to other expressions.

For example, this allows a list of conditions to be modified based on the gender of the patient

A unit that the user may choose when providing a quantity value.

​Provide either unitOption(s) or unitValueSet. If either of the extensions are present, the units for a Quantity element are constrained to only the units listed by the extensions - i.e. it is treated as a "required", not an "extensible" binding. In the absence of either, any unit is valid. See additional guidance and examples in the SDC implementation guide. If this extension present and an answer is provided for the question item in the QuestionnaireResponse, then the valueQuantity SHALL have a Quantity.code and Quantity.system that match the Coding.code and system of one of the allowed values if the Coding has a code and/or system. If the Coding only has a display, then the Quantity.unit must match. (Note that Coding with only a display is strongly discouraged.) If there is a match on code and system, but no match on display/unit, systems MAY raise a warning. However, because of translation and bandwidth considerations, some systems MAY opt to drop the unit or express it in an alternate language.

A set of units that the user may choose when providing a quantity value.

​Provide either unitOption(s) or unitValueSet. If either of the extensions are present, the units for a Quantity element are constrained to only the units listed by the extensions - i.e. it is treated as a "required", not an "extensible" binding. In the absence of either, any unit is valid. See additional guidance and examples in the SDC implementation guide. If this extension present and an answer is provided for the question item in the QuestionnaireResponse, then the valueQuantity SHALL have a Quantity.code and Quantity.system that match the Coding.code and system of one of the allowed values if the Coding has a code and/or system. If the Coding only has a display, then the Quantity.unit must match. (Note that Coding with only a display is strongly discouraged.) If there is a match on code and system, but no match on display/unit, systems MAY raise a warning. However, because of translation and bandwidth considerations, some systems MAY opt to drop the unit or express it in an alternate language. Validation of the Quantity unit MAY be performed by using the $validateCode operation, populating the elements passed into the operation from the Quantity.code, system and unit elements.

Indicates whether the list of supported units (conveyed in other extensions) are the exhaustive list from which the user must choose or whether they're able to select alternate codes or specify a string.

If the questionnaire-unit-open extension indicates that additional units other than the set of options provided for the question are allowed, this indicates the code system those units are expected to be drawn from. This extension SHOULD be present on any question where questionare-unit-open allows additional coded values.

Where the type for a question is "Reference", indicates a type of resource that is permitted.

​This extension only has meaning if the question.type = Reference. If no allowedResource extensions are present, the presumption is that any type of resource is permitted. If multiple are present, then any of the specified types are permitted. See additional guidance and examples in the SDC implementation guide.

Where the type for a question is "Reference", indicates a profile that the resource instances pointed to in answers to this question must be valid against.

​If multiple profiles are present, then the resource must be valid against at least one of them. See additional guidance and examples in the SDC implementation guide.

A FHIRPath or CQL expression, or FHIR Query that resolves to a list of candidate answers for the question item or that establishes context for a group item. The user may select from among the candidates to choose answers for the question.

The results of the expression must correspond to the item type of the question the element appears on or must correspond to a resource, backbone element or complex data type for a group item. Resources are considered a match for the Reference item type. Quantity can be a match for decimal and integer items so long as a questionnaire-unit extension is present. If the expression returns coded data, it *SHALL return the information as either code or Coding, not CodeableConcept. If the expression returns elements of type 'code', when the user selects one or more candidates, the code will be matched against the allowed Codings (from answerValueSet, answerOptions, or answerExpresssion). In this case, it is an error if there is more than one Coding with the same code.

For items of type reference, the reference can be populated either by picking an existing entity or by creating a new one. In the latter case, this Questionnaire allows specifying the Questionnaire to use in creating the target instance. Typically this will result in a QuestionnaireResponse that can be extracted to produce the desired resource. However, if the target resource for the reference is a QuestionnaireResponse, then the QuestionnaireResponse resulting from the Questionnaire can be referenced directly.

Specifies a constraint that is enforced on instantiated (or target) resources. This extension can be applied to definitional resources (such as ActivityDefinition or Measure) and indicates that the constraint should be enforced on resources that are instantiated from the definition.

Can be used on any definitional artifact to define a constraint that is enforced in the context of an instantiated resource. The constraint expression will have access to %target and %definition variables, where target is the instantiated resource, and definition is the definition used to instantiate.

Initial value for a question answer as determined by an evaluated expression.

Initial value is only calculated at the time the QuestionnaireResponse is first generated. If the expression returns coded data, it *SHALL return the information as either code or Coding, not CodeableConcept. If the expression returns elements of type 'code', when the user selects one or more candidates, the code will be matched against the allowed Codings (from answerValueSet, answerOptions, or answerExpression). In this case, it is an error if there is more than one Coding with the same code.

Calculated value for a question answer as determined by an evaluated expression.

Calculated value is updated as other answers in the QuestionnaireResponse are filled in.

An expression that returns a boolean value for whether to enable the item.

This is only permitted when the containing item does NOT have any enableWhen elements.

If the expression involves comparisons between elements that have different precisions but are otherwise equal, FHIRPath will resolve the expression to an empty set, which will in turn evaluate to false (meaning the item won't be enabled). If this is not the desired behavior, the author should add a .allTrue() to the end of the expression, which will result in an indeterminate outcome because of precision differences being handled as 'true' and the item being enabled. Questionnaires SHOULD be designed to take into account challenges around varying precision to minimize non-deterministic situations by setting constraints around expected precision, etc.

If the expression evaluates to something other than a boolean true or false, the Form Filler SHOULD still display the form, and if it does so, SHOULD treat the element as 'enabled' and display a warning to the user that the questionnaire logic was faulty and it's possible that the item shouldn't be enabled.

For string or text items, indicates the 'keyboard type' that should be used by the user interface to guide entry.

The assertion applies on a per item basis and is not inherited. If the item is 'text', only 'chat' should be declared if this extension is present.

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).

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.

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.

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

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.

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.

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.

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.

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.

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.).

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

Distinguishes groups from questions and display text and indicates data type for questions.

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

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

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.

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.

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).

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.

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.

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.

The criteria by which a question is enabled.

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

Allowed values to answer questions.

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.

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

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.

The actual value

An Extension

An expression that, when evaluated, provides the value for the element on which it appears.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

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)

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.

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

The actual value

An Extension

An expression that, when evaluated, provides the value for the element on which it appears.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

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

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.

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 actual value

An Extension

An expression that, when evaluated, provides the value for the element on which it appears.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

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.

Primitive value for canonical

An Extension

An expression that, when evaluated, provides the value for the element on which it appears.

​For questionnaires, see additional guidance and examples in the SDC implementation guide.

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.

An Extension

If true, indicates that if this answerOption is selected, no other possible answers may be selected, even if the item is a repeating question.

​See additional guidance and examples in the SDC implementation guide.

A numeric value that allows the comparison (less than, greater than) or other numerical manipulation of a concept (e.g. Adding up components of a score). Scores are usually a whole number, but occasionally decimals are encountered in scores. In the CodeSystem and ValueSet resources, the item weight is represented using the itemWeight property

NOTE: questionnaire.item.answerOption can have a type of Coding, potentially allowing two different scopes for this extension. In the case where answerOption is available, the weight SHALL be declared on the answerOption rather than on the answerOption.valueCoding.

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).

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.

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.

A potential answer that's allowed as the answer to this question.

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

Allowed values to answer questions.

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

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.

In some workflows, having defaults saves time.

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).

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.

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.

The actual value to for an initial answer.

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

Allowed values to answer questions.

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

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.

Reports can consist of complex nested groups.

Defines additional capabilities for controlling data entry and calculating values within the questionnaire.

A reference to a library containing cql used in this Questionnaire.

Allows variables to be calculated higher in the context of a QuestionnaireResponse for use with enableWhen-expression.