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FHIR Infrastructure Work GroupMaturity Level: 5Ballot Status: Trial Use
ElementDefinition
Definition

Captures constraints on each element within the resource, profile, or extension.

Control1..1
Summarytrue
InvariantsDefined on this element
eld-11: Binding can only be present for coded elements, string, and uri (expression : binding.empty() or type.code.empty() or type.select((code = 'code') or (code = 'Coding') or (code='CodeableConcept') or (code = 'Quantity') or (code = 'Extension') or (code = 'string') or (code = 'uri')).exists(), xpath: not(exists(f:binding)) or (count(f:type/f:code) = 0) or f:type/f:code/@value=('code','Coding','CodeableConcept','Quantity','Extension', 'string', 'uri'))
eld-13: Types must be unique by the combination of code and profile (expression : type.select(code&profile&targetProfile).isDistinct(), xpath: not(exists(for $type in f:type return $type/preceding-sibling::f:type[f:code/@value=$type/f:code/@value and f:profile/@value = $type/f:profile/@value])))
eld-14: Constraints must be unique by key (expression : constraint.select(key).isDistinct(), xpath: count(f:constraint) = count(distinct-values(f:constraint/f:key/@value)))
eld-15: default value and meaningWhenMissing are mutually exclusive (expression : defaultValue.empty() or meaningWhenMissing.empty(), xpath: not(exists(f:*[starts-with(local-name(.), 'fixed')])) or not(exists(f:meaningWhenMissing)))
eld-16: sliceName must be composed of proper tokens separated by "/" (expression : sliceName.empty() or sliceName.matches('^[a-zA-Z0-9\\/\\-\\_]+$'), xpath: not(exists(f:sliceName/@value)) or matches(f:sliceName/@value, '^[a-zA-Z0-9\\/\\-\\_]+$'))
eld-2: Min <= Max (expression : min.empty() or max.empty() or (max = '*') or (min <= max.toInteger()), xpath: not(exists(f:min)) or not(exists(f:max)) or (not(f:max/@value) and not(f:min/@value)) or (f:max/@value = '*') or (number(f:max/@value) >= f:min/@value))
eld-5: if the element definition has a contentReference, it cannot have type, defaultValue, fixed, pattern, example, minValue, maxValue, maxLength, or binding (expression : contentReference.empty() or (type.empty() and defaultValue.empty() and fixed.empty() and pattern.empty() and example.empty() and minValue.empty() and maxValue.empty() and maxLength.empty() and binding.empty()), xpath: not(exists(f:contentReference) and (exists(f:type) or exists(f:*[starts-with(local-name(.), 'value')]) or exists(f:*[starts-with(local-name(.), 'defaultValue')]) or exists(f:*[starts-with(local-name(.), 'fixed')]) or exists(f:*[starts-with(local-name(.), 'pattern')]) or exists(f:*[starts-with(local-name(.), 'example')]) or exists(f:*[starts-with(local-name(.), 'f:minValue')]) or exists(f:*[starts-with(local-name(.), 'f:maxValue')]) or exists(f:maxLength) or exists(f:binding))))
eld-6: Fixed value may only be specified if there is one type (expression : fixed.empty() or (type.count() <= 1), xpath: not(exists(f:*[starts-with(local-name(.), 'fixed')])) or (count(f:type)<=1))
eld-7: Pattern may only be specified if there is one type (expression : pattern.empty() or (type.count() <= 1), xpath: not(exists(f:*[starts-with(local-name(.), 'pattern')])) or (count(f:type)<=1))
eld-8: Pattern and value are mutually exclusive (expression : pattern.empty() or fixed.empty(), xpath: not(exists(f:*[starts-with(local-name(.), 'pattern')])) or not(exists(f:*[starts-with(local-name(.), 'fixed')])))
ElementDefinition.path
Definition

The path identifies the element and is expressed as a "."-separated list of ancestor elements, beginning with the name of the resource or extension.

Control1..1
Typestring
Summarytrue
ElementDefinition.representation
Definition

Codes that define how this element is represented in instances, when the deviation varies from the normal case.

Control0..*
Terminology BindingPropertyRepresentation (Required)
Typecode
Summarytrue
Comments

In resources, this is rarely used except for special cases where the representation deviates from the normal, and can only be done in the base standard (and profiles must reproduce what the base standard does). This element is used quite commonly in Logical models when the logical models represent a specific serialization format (e.g. CDA, v2 etc).

ElementDefinition.sliceName
Definition

The name of this element definition slice, when slicing is working. The name must be a token with no dots or spaces. This is a unique name referring to a specific set of constraints applied to this element, used to provide a name to different slices of the same element.

Control0..1
Typestring
Requirements

May also be used for code generation purposes.

Summarytrue
Comments

The name SHALL be unique within the structure within the context of the constrained resource element. (Though to avoid confusion, uniqueness across all elements is recommended.).

ElementDefinition.label
Definition

A single preferred label which is the text to display beside the element indicating its meaning or to use to prompt for the element in a user display or form.

Control0..1
Typestring
Summarytrue
Comments

See also the extension (http://hl7.org/fhir/StructureDefinition/elementdefinition-question)[extension-elementdefinition-question.html].

ElementDefinition.code
Definition

A code that has the same meaning as the element in a particular terminology.

Control0..*
Terminology BindingLOINC Codes (Example)
TypeCoding
Requirements

Links the meaning of an element to an external terminology, and is very useful for searching and indexing.

Summarytrue
Comments

The concept SHALL be properly aligned with the data element definition and other constraints, as defined in the code system, including relationships, of any code listed here. Where multiple codes exist in a terminology that could correspond to the data element, the most granular code(s) should be selected, so long as they are not more restrictive than the data element itself. The mappings may be used to provide more or less granular or structured equivalences in the code system.

LOINC CodeLOINC_NUM
ElementDefinition.slicing
Definition

Indicates that the element is sliced into a set of alternative definitions (i.e. in a structure definition, there are multiple different constraints on a single element in the base resource). Slicing can be used in any resource that has cardinality ..* on the base resource, or any resource with a choice of types. The set of slices is any elements that come after this in the element sequence that have the same path, until a shorter path occurs (the shorter path terminates the set).

Control0..1
Summarytrue
Comments

The first element in the sequence, the one that carries the slicing, is the definition that applies to all the slices. This is based on the unconstrained element, but can apply any constraints as appropriate. This may include the common constraints on the children of the element.

InvariantsDefined on this element
eld-1: If there are no discriminators, there must be a definition (expression : discriminator.exists() or description.exists(), xpath: (f:discriminator) or (f:description))
ElementDefinition.slicing.discriminator
Definition

Designates which child elements are used to discriminate between the slices when processing an instance. If one or more discriminators are provided, the value of the child elements in the instance data SHALL completely distinguish which slice the element in the resource matches based on the allowed values for those elements in each of the slices.

Control0..*
Summarytrue
Comments

If there is no discriminator, the content is hard to process, so this should be avoided. If the base element has a cardinality of ..1, and there is a choice of types, the discriminator must be "@type".

ElementDefinition.slicing.discriminator.type
Definition

How the element value is interpreted when discrimination is evaluated.

Control1..1
Terminology BindingDiscriminatorType (Required)
Typecode
Summarytrue
ElementDefinition.slicing.discriminator.path
Definition

A FHIRPath expression, using a restricted subset of FHIRPath, that is used to identify the element on which discrimination is based.

Control1..1
Typestring
Summarytrue
Comments

The only FHIRPath functions that are allowed are resolve(), and extension(url).

ElementDefinition.slicing.description
Definition

A human-readable text description of how the slicing works. If there is no discriminator, this is required to be present to provide whatever information is possible about how the slices can be differentiated.

Control0..1
Typestring
Summarytrue
Comments

If it's really not possible to differentiate them, the design should be re-evaluated to make the content usable.

InvariantsAffect this element
eld-1: If there are no discriminators, there must be a definition (expression : discriminator.exists() or description.exists(), xpath: (f:discriminator) or (f:description))
ElementDefinition.slicing.ordered
Definition

If the matching elements have to occur in the same order as defined in the profile.

Control0..1
Typeboolean
Default Valuefalse
Summarytrue
Comments

Order should only be required when it is a pressing concern for presentation. Profile authors should consider making the order a feature of the rules about the narrative, not the rules about the data - requiring ordered data makes the profile much less re-usable.

ElementDefinition.slicing.rules
Definition

Whether additional slices are allowed or not. When the slices are ordered, profile authors can also say that additional slices are only allowed at the end.

Control1..1
Terminology BindingSlicingRules (Required)
Typecode
Summarytrue
Comments

Allowing additional elements makes for a much for flexible template - it's open for use in wider contexts, but also means that the content of the resource is not closed, and applications have to decide how to handle content not described by the profile.

ElementDefinition.short
Definition

A concise description of what this element means (e.g. for use in autogenerated summaries).

Control0..1
Typestring
Summarytrue
Comments

May change the term to provide language more appropriate to the context of the profile or to reflect slicing.

ElementDefinition.definition
Definition

Provides a complete explanation of the meaning of the data element for human readability. For the case of elements derived from existing elements (e.g. constraints), the definition SHALL be consistent with the base definition, but convey the meaning of the element in the particular context of use of the resource.

Control0..1
Typemarkdown
Requirements

To allow a user to state the usage of an element in a particular context.

Alternate NamesDescription
Summarytrue
Comments

It is easy for a different definition to change the meaning of an element and this can have nasty downstream consequences. Please be careful when providing definitions.

LOINC CodeTERM DEFINITION/DESCRIPTION(S)
ElementDefinition.comment
Definition

Explanatory notes and implementation guidance about the data element, including notes about how to use the data properly, exceptions to proper use, etc.

Control0..1
Typemarkdown
Summarytrue
Comments

If it is possible to capture usage rules using constraints, that mechanism should be used in preference to this element.

LOINC CodeCOMMENTS
ElementDefinition.requirements
Definition

This element is for traceability of why the element was created and why the constraints exist as they do. This may be used to point to source materials or specifications that drove the structure of this element.

Control0..1
Typemarkdown
Summarytrue
Comments

This element does not describe the usage of the element (that's done in comments), rather it's for traceability of why the element is either needed or why the constraints exist as they do. This may be used to point to source materials or specifications that drove the structure of this data element.

LOINC CodeR/O/C
ElementDefinition.alias
Definition

Identifies additional names by which this element might also be known.

Control0..*
Typestring
Requirements

Allows for better easier recognition of the element by multiple communities, including international communities.

Alternate Namessynonym; other name
Summarytrue
LOINC CodeRELATED NAMES (only some of these apply)
ElementDefinition.min
Definition

The minimum number of times this element SHALL appear in the instance.

Control0..1
TypeunsignedInt
Summarytrue
InvariantsAffect this element
eld-2: Min <= Max (expression : min.empty() or max.empty() or (max = '*') or (min <= max.toInteger()), xpath: not(exists(f:min)) or not(exists(f:max)) or (not(f:max/@value) and not(f:min/@value)) or (f:max/@value = '*') or (number(f:max/@value) >= f:min/@value))
ElementDefinition.max
Definition

The maximum number of times this element is permitted to appear in the instance.

Control0..1
Typestring
Summarytrue
InvariantsDefined on this element
eld-3: Max SHALL be a number or "*" (expression : empty() or ($this = '*') or (toInteger() >= 0), xpath: @value='*' or (normalize-space(@value)!='' and normalize-space(translate(@value, '0123456789',''))=''))
Affect this element
eld-2: Min <= Max (expression : min.empty() or max.empty() or (max = '*') or (min <= max.toInteger()), xpath: not(exists(f:min)) or not(exists(f:max)) or (not(f:max/@value) and not(f:min/@value)) or (f:max/@value = '*') or (number(f:max/@value) >= f:min/@value))
ElementDefinition.base
Definition

Information about the base definition of the element, provided to make it unnecessary for tools to trace the deviation of the element through the derived and related profiles. This information is provided when the element definition is not the original definition of an element - i.g. either in a constraint on another type, or for elements from a super type in a snap shot.

Control0..1
Summarytrue
Comments

The base information does not carry any information that could not be determined from the path and related profiles, but making this determination requires both that the related profiles are available, and that the algorithm to determine them be available. So they are deformalised into this location for tooling convenience, and to ensure that the base information is available without dependencies.

ElementDefinition.base.path
Definition

The Path that identifies the base element - this matches the ElementDefinition.path for that element. Across FHIR, there is only one base definition of any element - that is, an element definition on a StructureDefinition without a StructureDefinition.base.

Control1..1
Typestring
Summarytrue
ElementDefinition.base.min
Definition

Minimum cardinality of the base element identified by the path.

Control1..1
TypeunsignedInt
Summarytrue
Comments

This is provided for consistency with max, and may affect code generation of mandatory elements of the base resource are generated differently (some reference implementations have done this).

ElementDefinition.base.max
Definition

Maximum cardinality of the base element identified by the path.

Control1..1
Typestring
Summarytrue
Comments

This is provided to code generation, since the serialization representation in JSON differs depending on whether the base element has max > 1. Also, some forms of code generation may differ.

ElementDefinition.contentReference
Definition

Identifies the identity of an element defined elsewhere in the profile whose content rules should be applied to the current element.

Control0..1
Typeuri
Summarytrue
InvariantsAffect this element
eld-5: if the element definition has a contentReference, it cannot have type, defaultValue, fixed, pattern, example, minValue, maxValue, maxLength, or binding (expression : contentReference.empty() or (type.empty() and defaultValue.empty() and fixed.empty() and pattern.empty() and example.empty() and minValue.empty() and maxValue.empty() and maxLength.empty() and binding.empty()), xpath: not(exists(f:contentReference) and (exists(f:type) or exists(f:*[starts-with(local-name(.), 'value')]) or exists(f:*[starts-with(local-name(.), 'defaultValue')]) or exists(f:*[starts-with(local-name(.), 'fixed')]) or exists(f:*[starts-with(local-name(.), 'pattern')]) or exists(f:*[starts-with(local-name(.), 'example')]) or exists(f:*[starts-with(local-name(.), 'f:minValue')]) or exists(f:*[starts-with(local-name(.), 'f:maxValue')]) or exists(f:maxLength) or exists(f:binding))))
ElementDefinition.type
Definition

The data type or resource that the value of this element is permitted to be.

Control0..*
Summarytrue
Comments

The Type of the element can be left blank in a differential constraint, in which case the type is inherited from the resource. Abstract types are not permitted to appear as a type when multiple types are listed. (I.e. Abstract types cannot be part of a choice).

InvariantsDefined on this element
eld-4: Aggregation may only be specified if one of the allowed types for the element is a resource (expression : aggregation.empty() or (code = 'Reference'), xpath: not(exists(f:aggregation)) or exists(f:code[@value = 'Reference']))
Affect this element
eld-13: Types must be unique by the combination of code and profile (expression : type.select(code&profile&targetProfile).isDistinct(), xpath: not(exists(for $type in f:type return $type/preceding-sibling::f:type[f:code/@value=$type/f:code/@value and f:profile/@value = $type/f:profile/@value])))
LOINC CodeHL7_V2_DATATYPE (translation required), HL7_V3_DATATYPE (translation required)
ElementDefinition.type.code
Definition

URL of Data type or Resource that is a(or the) type used for this element. References are URLs that are relative to http://hl7.org/fhir/StructureDefinition e.g. "string" is a reference to http://hl7.org/fhir/StructureDefinition/string. Absolute URLs are only allowed in logical models.

Control1..1
Terminology BindingFHIRDefinedType (Extensible)
Typeuri
Summarytrue
Comments

If the element is a reference to another resource, this element contains "Reference", and the targetProfile element defines what resources can be referenced. The targetProfile may be a reference to the general definition of a resource (e.g. http://hl7.org/fhir/StructureDefinition/Patient). There would be one pair of type/code for each allowed target resource type.

LOINC CodeHL7_V2_DATATYPE (translation required), HL7_V3_DATATYPE (translation required)
ElementDefinition.type.profile
Definition

Identifies a profile structure or implementation Guide that SHALL hold for the datatype this element refers to. Can be a local reference - to a contained StructureDefinition, or a reference to another StructureDefinition or Implementation Guide by a canonical URL. When an implementation guide is specified, the resource SHALL conform to at least one profile defined in the implementation guide.

Control0..1
Typeuri
Summarytrue
ElementDefinition.type.targetProfile
Definition

Identifies a profile structure or implementation Guide that SHALL hold for the target of the reference this element refers to. Can be a local reference - to a contained StructureDefinition, or a reference to another StructureDefinition or Implementation Guide by a canonical URL. When an implementation guide is specified, the resource SHALL conform to at least one profile defined in the implementation guide.

Control0..1
Typeuri
Summarytrue
ElementDefinition.type.aggregation
Definition

If the type is a reference to another resource, how the resource is or can be aggregated - is it a contained resource, or a reference, and if the context is a bundle, is it included in the bundle.

Control0..*
Terminology BindingAggregationMode (Required)
Typecode
Summarytrue
InvariantsAffect this element
eld-4: Aggregation may only be specified if one of the allowed types for the element is a resource (expression : aggregation.empty() or (code = 'Reference'), xpath: not(exists(f:aggregation)) or exists(f:code[@value = 'Reference']))
ElementDefinition.type.versioning
Definition

Whether this reference needs to be version specific or version independent, or whether either can be used.

Control0..1
Terminology BindingReferenceVersionRules (Required)
Typecode
Default Valueeither
Summarytrue
Comments

The base specification never makes a rule as to which form is allowed, but implementation guides may do this.

ElementDefinition.defaultValue[x]
Definition

The value that should be used if there is no value stated in the instance (e.g. 'if not otherwise specified, the abstract is false').

Control0..1
Type*
[x] NoteSee Choice of Data Types for further information about how to use [x]
Summarytrue
Comments

Default values can only be specified on a resource, data type, or extension definition, and never in a profile that applies to one of these. Specifying a default value means that the property can never been unknown - it must always have a value. Further, the default value can never be changed. For these reasons, default values are (and should be) used extremely sparingly.

InvariantsAffect this element
eld-15: default value and meaningWhenMissing are mutually exclusive (expression : defaultValue.empty() or meaningWhenMissing.empty(), xpath: not(exists(f:*[starts-with(local-name(.), 'fixed')])) or not(exists(f:meaningWhenMissing)))
ElementDefinition.meaningWhenMissing
Definition

The Implicit meaning that is to be understood when this element is missing (e.g. 'when this element is missing, the period is ongoing'.

Control0..1
Typemarkdown
Summarytrue
Comments

Implicit meanings for missing values can only be specified on a resource, data type, or extension definition, and never in a profile that applies to one of these. An implicit meaning for a missing value can never be changed, and specifying one has the consequence that constraining its use in profiles eliminates use cases as possibilities, not merely moving them out of scope.

InvariantsAffect this element
eld-15: default value and meaningWhenMissing are mutually exclusive (expression : defaultValue.empty() or meaningWhenMissing.empty(), xpath: not(exists(f:*[starts-with(local-name(.), 'fixed')])) or not(exists(f:meaningWhenMissing)))
ElementDefinition.orderMeaning
Definition

If present, indicates that the order of the repeating element has meaning and describes what that meaning is. If absent, it means that the order of the element has no meaning.

Control0..1
Typestring
Summarytrue
Comments

This element can only be asserted on repeating elements and can only be introduced when defining resources or data types. It can be further refined profiled elements but if absent in the base type, a profile cannot assert meaning.

ElementDefinition.fixed[x]
Definition

Specifies a value that SHALL be exactly the value for this element in the instance. For purposes of comparison, non-significant whitespace is ignored, and all values must be an exact match (case and accent sensitive). Missing elements/attributes must also be missing.

Control0..1
Type*
[x] NoteSee Choice of Data Types for further information about how to use [x]
Summarytrue
Comments

This is not recommended for Coding and CodeableConcept since these often have highly contextual properties such as version or display.

InvariantsAffect this element
eld-5: if the element definition has a contentReference, it cannot have type, defaultValue, fixed, pattern, example, minValue, maxValue, maxLength, or binding (expression : contentReference.empty() or (type.empty() and defaultValue.empty() and fixed.empty() and pattern.empty() and example.empty() and minValue.empty() and maxValue.empty() and maxLength.empty() and binding.empty()), xpath: not(exists(f:contentReference) and (exists(f:type) or exists(f:*[starts-with(local-name(.), 'value')]) or exists(f:*[starts-with(local-name(.), 'defaultValue')]) or exists(f:*[starts-with(local-name(.), 'fixed')]) or exists(f:*[starts-with(local-name(.), 'pattern')]) or exists(f:*[starts-with(local-name(.), 'example')]) or exists(f:*[starts-with(local-name(.), 'f:minValue')]) or exists(f:*[starts-with(local-name(.), 'f:maxValue')]) or exists(f:maxLength) or exists(f:binding))))
eld-6: Fixed value may only be specified if there is one type (expression : fixed.empty() or (type.count() <= 1), xpath: not(exists(f:*[starts-with(local-name(.), 'fixed')])) or (count(f:type)<=1))
eld-8: Pattern and value are mutually exclusive (expression : pattern.empty() or fixed.empty(), xpath: not(exists(f:*[starts-with(local-name(.), 'pattern')])) or not(exists(f:*[starts-with(local-name(.), 'fixed')])))
ElementDefinition.pattern[x]
Definition

Specifies a value that the value in the instance SHALL follow - that is, any value in the pattern must be found in the instance. Other additional values may be found too. This is effectively constraint by example. The values of elements present in the pattern must match exactly (case-sensitive, accent-sensitive, etc.).

Control0..1
Type*
[x] NoteSee Choice of Data Types for further information about how to use [x]
Summarytrue
Comments

Mostly used for fixing values of CodeableConcept. At present, pattern[x] is not recommended as a basis for slicing while issues related to this are investigated during the STU period.

InvariantsAffect this element
eld-5: if the element definition has a contentReference, it cannot have type, defaultValue, fixed, pattern, example, minValue, maxValue, maxLength, or binding (expression : contentReference.empty() or (type.empty() and defaultValue.empty() and fixed.empty() and pattern.empty() and example.empty() and minValue.empty() and maxValue.empty() and maxLength.empty() and binding.empty()), xpath: not(exists(f:contentReference) and (exists(f:type) or exists(f:*[starts-with(local-name(.), 'value')]) or exists(f:*[starts-with(local-name(.), 'defaultValue')]) or exists(f:*[starts-with(local-name(.), 'fixed')]) or exists(f:*[starts-with(local-name(.), 'pattern')]) or exists(f:*[starts-with(local-name(.), 'example')]) or exists(f:*[starts-with(local-name(.), 'f:minValue')]) or exists(f:*[starts-with(local-name(.), 'f:maxValue')]) or exists(f:maxLength) or exists(f:binding))))
eld-7: Pattern may only be specified if there is one type (expression : pattern.empty() or (type.count() <= 1), xpath: not(exists(f:*[starts-with(local-name(.), 'pattern')])) or (count(f:type)<=1))
eld-8: Pattern and value are mutually exclusive (expression : pattern.empty() or fixed.empty(), xpath: not(exists(f:*[starts-with(local-name(.), 'pattern')])) or not(exists(f:*[starts-with(local-name(.), 'fixed')])))
ElementDefinition.example
Definition

A sample value for this element demonstrating the type of information that would typically be found in the element.

Control0..*
Summarytrue
Comments

Examples will most commonly be present for data where it's not implicitly obvious from either the data type or value set what the values might be. (I.e. Example values for dates or quantities would generally be unnecessary.) If the example value is fully populated, the publication tool can generate an instance automatically.

ElementDefinition.example.label
Definition

Describes the purpose of this example amoung the set of examples.

Control1..1
Typestring
Summarytrue
ElementDefinition.example.value[x]
Definition

The actual value for the element, which must be one of the types allowed for this element.

Control1..1
Type*
[x] NoteSee Choice of Data Types for further information about how to use [x]
Summarytrue
LOINC CodeEXMPL_ANSWERS
ElementDefinition.minValue[x]
Definition

The minimum allowed value for the element. The value is inclusive. This is allowed for the types date, dateTime, instant, time, decimal, integer, and Quantity.

Control0..1
Typedate|dateTime|instant|time|decimal|integer|positiveInt|unsignedInt|Quantity
[x] NoteSee Choice of Data Types for further information about how to use [x]
Summarytrue
Comments

Except for date/date/instant, the type of the minValue[x] SHALL be the same as the specified type of the element. For the date/dateTime/instant values, the type of minValue[x] SHALL be either the same, or a a Duration which specifies a relative time limit to the current time. The duration value is positive, and is subtracted from the current clock to determine the minimum allowable value. A minimum value for a Quantity is interpreted as an canonical minimum - e.g. you cannot provide 100mg if the minimum value is 10g.

ElementDefinition.maxValue[x]
Definition

The maximum allowed value for the element. The value is inclusive. This is allowed for the types date, dateTime, instant, time, decimal, integer, and Quantity.

Control0..1
Typedate|dateTime|instant|time|decimal|integer|positiveInt|unsignedInt|Quantity
[x] NoteSee Choice of Data Types for further information about how to use [x]
Summarytrue
Comments

Except for date/date/instant, the type of the maxValue[x] SHALL be the same as the specified type of the element. For the date/dateTime/instant values, the type of maxValue[x] SHALL be either the same, or a a Duration which specifies a relative time limit to the current time. The duration value is positive, and is added to the current clock to determine the maximum allowable value. A maximum value for a Quantity is interpreted as an canonical maximum - e.g. you cannot provide 10g if the maximum value is 50mg.

ElementDefinition.maxLength
Definition

Indicates the maximum length in characters that is permitted to be present in conformant instances and which is expected to be supported by conformant consumers that support the element.

Control0..1
Typeinteger
Summarytrue
Comments

Receivers are not required to reject instances that exceed the maximum length. The full length could be stored. In some cases, data might be truncated, though truncation should be undertaken with care and an understanding of the consequences of doing so. If not specified, there is no conformance expectation for length support.

ElementDefinition.condition
Definition

A reference to an invariant that may make additional statements about the cardinality or value in the instance.

Control0..*
Typeid
Summarytrue
ElementDefinition.constraint
Definition

Formal constraints such as co-occurrence and other constraints that can be computationally evaluated within the context of the instance.

Control0..*
Summarytrue
Comments

Constraints should be declared on the "context" element - the lowest element in the hierarchy that is common to all nodes referenced by the constraint.

ElementDefinition.constraint.key
Definition

Allows identification of which elements have their cardinalities impacted by the constraint. Will not be referenced for constraints that do not affect cardinality.

Control1..1
Typeid
Summarytrue
InvariantsAffect this element
eld-14: Constraints must be unique by key (expression : constraint.select(key).isDistinct(), xpath: count(f:constraint) = count(distinct-values(f:constraint/f:key/@value)))
ElementDefinition.constraint.requirements
Definition

Description of why this constraint is necessary or appropriate.

Control0..1
Typestring
Summarytrue
Comments

To be used if the reason for the constraint may not be intuitive to all implementers.

ElementDefinition.constraint.severity
Definition

Identifies the impact constraint violation has on the conformance of the instance.

Control1..1
Terminology BindingConstraintSeverity (Required)
Typecode
Summarytrue
Comments

This allows constraints to be asserted as "shall" (error) and "should" (warning).

ElementDefinition.constraint.human
Definition

Text that can be used to describe the constraint in messages identifying that the constraint has been violated.

Control1..1
Typestring
Summarytrue
Comments

Should be expressed in business terms as much as possible.

ElementDefinition.constraint.expression
Definition

A FHIRPath expression of constraint that can be executed to see if this constraint is met.

Control1..1
Typestring
Requirements

Used by validation tooling tests of the validity of the resource.

Summarytrue
ElementDefinition.constraint.xpath
Definition

An XPath expression of constraint that can be executed to see if this constraint is met.

Control0..1
Typestring
Requirements

Used in Schematron tests of the validity of the resource.

Summarytrue
Comments

Elements SHALL use "f" as the namespace prefix for the FHIR namespace, and "x" for the xhtml namespace, and SHALL NOT use any other prefixes.

Note: we are considering deprecating the xpath element. Implementer feedback is welcome.

ElementDefinition.constraint.source
Definition

A reference to the original source of the constraint, for traceability purposes.

Control0..1
Typeuri
Summarytrue
Comments

This is used when, e.g. rendering, where it is not useful to present inherited constraints when rendering the snapshot.

ElementDefinition.mustSupport
Definition

If true, implementations that produce or consume resources SHALL provide "support" for the element in some meaningful way. If false, the element may be ignored and not supported.

Control0..1
Typeboolean
Default Valuefalse
Requirements

Allows a profile to set expectations for system capabilities beyond merely respecting cardinality constraints.

Summarytrue
Comments

"Something useful" is context dependent and impossible to describe in the base FHIR specification. For this reason, tue mustSupport flag is never set to true by the FHIR specification itself - it is only set to true in profiles.

This is done in Resource Profiles, where the profile labels an element as mustSupport=true. When a profile does this, it SHALL also make clear exactly what kind of "support" is required, as this can mean many things.

Note that an element that has the property IsModifier is not necessarily a "key" element (e.g. one of the important elements to make use of the resource), nor is it automatically mustSupport - however both of these things are more likely to be true for IsModifier elements than for other elements.

ElementDefinition.isModifier
Definition

If true, the value of this element affects the interpretation of the element or resource that contains it, and the value of the element cannot be ignored. Typically, this is used for status, negation and qualification codes. The effect of this is that the element cannot be ignored by systems: they SHALL either recognize the element and process it, and/or a pre-determination has been made that it is not relevant to their particular system.

Control0..1
Typeboolean
Default Valuefalse
Requirements

Allows elements to be introduced into a specification that can't safely be ignored by applications that don't recognize them.

Summarytrue
Comments

Only the definition of an element can set IsModifier true - either the specification itself or where an extension is originally defined. Once set, it cannot be changed in derived profiles. An element/extension that has isModifier=true SHOULD also have a minimum cardinality of 1, so that there is no lack of clarity about what to do if it is missing. If it can be missing, the definition SHALL make the meaning of a missing element clear.

ElementDefinition.isSummary
Definition

Whether the element should be included if a client requests a search with the parameter _summary=true.

Control0..1
Typeboolean
Default Valuefalse
Requirements

Allow clients to search through large resources quickly.

Summarytrue
Comments

Some resources include a set of simple metadata, and some very large data. This element is used to reduce the quantity of data returned in searches. Note that servers may pre-cache summarized resources for optimal performance, so servers may not support per-profile use of the isSummary flag. When a request is made with _summary=true, serailisers only include elements marked as 'isSummary = true'. Other than Attachment.data, all data type properties are included in the summary form. Modifier elements or elements with minimum cardinality = 1 must be marked as summary elements.

ElementDefinition.binding
Definition

Binds to a value set if this element is coded (code, Coding, CodeableConcept, Quantity), or the data types (string, uri).

Control0..1
Summarytrue
Comments

For a CodeableConcept, when no codes are allowed - only text, use a binding of strength "required" with a description explaining that no coded values are allowed and what sort of information to put in the "text" element.

InvariantsDefined on this element
eld-10: provide either a reference or a description (or both) (expression : valueSet.exists() or description.exists(), xpath: (exists(f:valueSetUri) or exists(f:valueSetReference)) or exists(f:description))
eld-12: ValueSet as a URI SHALL start with http:// or https:// or urn: (expression : valueSet.is(uri).not() or valueSet.as(uri).startsWith('http:') or valueSet.as(uri).startsWith('https') or valueSet.as(uri).startsWith('urn:'), xpath: not(exists(f:valueSetUri)) or (starts-with(string(f:valueSetUri/@value), 'http:') or starts-with(string(f:valueSetUri/@value), 'https:') or starts-with(string(f:valueSetUri/@value), 'urn:')))
Affect this element
eld-11: Binding can only be present for coded elements, string, and uri (expression : binding.empty() or type.code.empty() or type.select((code = 'code') or (code = 'Coding') or (code='CodeableConcept') or (code = 'Quantity') or (code = 'Extension') or (code = 'string') or (code = 'uri')).exists(), xpath: not(exists(f:binding)) or (count(f:type/f:code) = 0) or f:type/f:code/@value=('code','Coding','CodeableConcept','Quantity','Extension', 'string', 'uri'))
LOINC CodeANSWER LIST, NORMATIVE ANSWER LIST
ElementDefinition.binding.strength
Definition

Indicates the degree of conformance expectations associated with this binding - that is, the degree to which the provided value set must be adhered to in the instances.

Control1..1
Terminology BindingBindingStrength (Required)
Typecode
Alternate Namesconformance; extensibility
Summarytrue
Comments

For further discussion, see Using Terminologies.

LOINC CodeN/A
ElementDefinition.binding.description
Definition

Describes the intended use of this particular set of codes.

Control0..1
Typestring
Summarytrue
InvariantsAffect this element
eld-10: provide either a reference or a description (or both) (expression : valueSet.exists() or description.exists(), xpath: (exists(f:valueSetUri) or exists(f:valueSetReference)) or exists(f:description))
ElementDefinition.binding.valueSet[x]
Definition

Points to the value set or external definition (e.g. implicit value set) that identifies the set of codes to be used. If the binding refers to an explicit value set - the normal case - then use a Reference(ValueSet) preferably containing the canonical URL for the value set. If the reference is to an implicit value set - usually, an IETF RFC that defines a grammar, such as mime types - then use a uri.

Control0..1
Typeuri|Reference(ValueSet)
[x] NoteSee Choice of Data Types for further information about how to use [x]
Summarytrue
Comments

For value sets with a referenceResource, the display can contain the value set description. The reference may be version-specific or not.

InvariantsAffect this element
eld-10: provide either a reference or a description (or both) (expression : valueSet.exists() or description.exists(), xpath: (exists(f:valueSetUri) or exists(f:valueSetReference)) or exists(f:description))
eld-12: ValueSet as a URI SHALL start with http:// or https:// or urn: (expression : valueSet.is(uri).not() or valueSet.as(uri).startsWith('http:') or valueSet.as(uri).startsWith('https') or valueSet.as(uri).startsWith('urn:'), xpath: not(exists(f:valueSetUri)) or (starts-with(string(f:valueSetUri/@value), 'http:') or starts-with(string(f:valueSetUri/@value), 'https:') or starts-with(string(f:valueSetUri/@value), 'urn:')))
LOINC CodeCODE_TABLE
ElementDefinition.mapping
Definition

Identifies a concept from an external specification that roughly corresponds to this element.

Control0..*
Requirements

Provides guidance to implementers familiar with or converting content from other specifications.

Summarytrue
Comments

Mappings are not necessarily specific enough for safe translation.

ElementDefinition.mapping.identity
Definition

An internal reference to the definition of a mapping.

Control1..1
Typeid
Summarytrue
ElementDefinition.mapping.language
Definition

Identifies the computable language in which mapping.map is expressed.

Control0..1
Terminology BindingMimeType :
Typecode
Summarytrue
Comments

If omitted, then there can be no expectation of computational interpretation of the mapping.

ElementDefinition.mapping.map
Definition

Expresses what part of the target specification corresponds to this element.

Control1..1
Typestring
Summarytrue
Comments

For most mappings, the syntax is undefined. Syntax will be provided for mappings to the RIM. Multiple mappings may be possible and may include constraints on other resource elements that identify when a particular mapping applies.

ElementDefinition.mapping.comment
Definition

Comments that provide information about the mapping or its use.

Control0..1
Typestring
Summarytrue