It is the central piece of the View Layer and represents a tabular projection of FHIR resources with the columns and filtering criteria defined by FHIRPath expressions. The logical model is described below.

Key Elements

Resource

Each ViewDefinition instance is tied to a single FHIR resource type, such as Patient or Observation. It will then create zero or more rows for each resource instance. Examples include simple tabular views of patients, unrolling patient addresses into an address table, views of certain types of observations, and so on.

Select

Each ViewDefinition instance has a select that specifies the content and names for the columns in the view. The content for each column is defined with FHIRPath expressions that return specific data elements from the FHIR resources.

Where

The ViewDefinition may include one or more where clauses that may be used to further limit, or filter, the resources included in the view. For instance, users may have different views for blood pressure observations or other observation types.

Constants

The ViewDefinition may include one or more constants, which are simply values that can be reused in FHIRPath expressions.

View Runner

A View Runner implementation can execute a ViewDefinition and return the results as a table that can be used for further processing using the user's chosen tech stack. See System Layers for details.

Profiling

ViewDefinitions may be profiled to meet specific needs. For instance, the Shareable View Definition profile adds constraints for ViewDefinitions intended to be shared between systems. Implementers may create their own ViewDefinition profiles for further specialized needs.

• Key Elements Table
• Differential Table
• Snapshot Table
• Statistics/References
• All

Name	Flags	Card.	Type	Description & Constraints
ViewDefinition	C	1..1	CanonicalResource	Elements defined in Ancestors:id, meta, implicitRules, language, text, contained, extension, modifierExtension, url, identifier, version, versionAlgorithm[x], name, title, status, experimental, date, publisher, contact, description, useContext, jurisdiction, purpose, copyright, copyrightLabel View Definition cnl-0: Name should be usable as an identifier for the module by machine processing applications such as code generation dom-2: If the resource is contained in another resource, it SHALL NOT contain nested Resources dom-3: If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource dom-4: If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated dom-5: If a resource is contained in another resource, it SHALL NOT have a security label dom-6: A resource should have narrative for robust management
id	Σ	0..1	id	Logical id of this artifact
meta	Σ	0..1	Meta	Metadata about the resource ele-1: All FHIR elements must have a @value or children
implicitRules	?!Σ	0..1	uri	A set of rules under which this content was created ele-1: All FHIR elements must have a @value or children
language		0..1	code	Language of the resource content Binding: AllLanguages (required): IETF language tag for a human language Additional Bindings Purpose CommonLanguages Starter Set ele-1: All FHIR elements must have a @value or children
text		0..1	Narrative	Text summary of the resource, for human interpretation ele-1: All FHIR elements must have a @value or children
contained		0..*	Resource	Contained, inline Resources
extension		0..*	Extension	Additional content defined by implementations ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
url	ΣC	0..1	uri	Canonical identifier for this {{title}}, represented as an absolute URI (globally unique) cnl-1: URL should not contain | or # - these characters make processing canonical references problematic ele-1: All FHIR elements must have a @value or children
identifier	Σ	0..*	Identifier	Additional identifier for the {{title}} ele-1: All FHIR elements must have a @value or children
version	Σ	0..1	string	Business version of the {{title}} ele-1: All FHIR elements must have a @value or children
versionAlgorithm[x]	Σ	0..1		How to compare versions Binding: VersionAlgorithm (extensible) ele-1: All FHIR elements must have a @value or children
versionAlgorithmString			string
versionAlgorithmCoding			Coding
name	ΣC	0..1	string	Name for this {{title}} (computer friendly) ele-1: All FHIR elements must have a @value or children sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
title	Σ	0..1	string	Name for this {{title}} (human friendly) ele-1: All FHIR elements must have a @value or children
status	?!Σ	1..1	code	draft | active | retired | unknown Binding: PublicationStatus (required): The lifecycle status of an artifact. ele-1: All FHIR elements must have a @value or children
experimental	Σ	0..1	boolean	For testing purposes, not real usage ele-1: All FHIR elements must have a @value or children
date	Σ	0..1	dateTime	Date last changed ele-1: All FHIR elements must have a @value or children
publisher	Σ	0..1	string	Name of the publisher/steward (organization or individual) ele-1: All FHIR elements must have a @value or children
contact	Σ	0..*	ContactDetail	Contact details for the publisher ele-1: All FHIR elements must have a @value or children
description		0..1	markdown	Natural language description of the {{title}} ele-1: All FHIR elements must have a @value or children
useContext	Σ	0..*	UsageContext	The context that the content is intended to support ele-1: All FHIR elements must have a @value or children
jurisdiction	Σ	0..*	CodeableConcept	Intended jurisdiction for {{title}} (if applicable) Binding: JurisdictionValueSet (extensible): Countries and regions within which this artifact is targeted for use. ele-1: All FHIR elements must have a @value or children
purpose		0..1	markdown	Why this {{title}} is defined ele-1: All FHIR elements must have a @value or children
copyright		0..1	markdown	Use and/or publishing restrictions ele-1: All FHIR elements must have a @value or children
copyrightLabel		0..1	string	Copyright holder and year(s) ele-1: All FHIR elements must have a @value or children
resource		1..1	code	FHIR resource for the ViewDefinition Binding: ResourceType (required)
profile		0..*	canonical(StructureDefinition)	FHIR profiles that this view definition was intended to be executed against
fhirVersion		0..*	code	FHIR version(s) of the resource for the ViewDefinition Binding: FHIRVersion (required)
constant		0..*	BackboneElement	Constant that can be used in FHIRPath expressions ele-1: All FHIR elements must have a @value or children
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
name	C	1..1	string	Name of constant (referred to in FHIRPath as %[name]) sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
value[x]		1..1		Value of constant
valueBase64Binary			base64Binary
valueBoolean			boolean
valueCanonical			canonical(Any)
valueCode			code
valueDate			date
valueDateTime			dateTime
valueDecimal			decimal
valueId			id
valueInstant			instant
valueInteger			integer
valueInteger64			integer64
valueOid			oid
valueString			string
valuePositiveInt			positiveInt
valueTime			time
valueUnsignedInt			unsignedInt
valueUri			uri
valueUrl			url
valueUuid			uuid
select	C	1..*	BackboneElement	A collection of columns and nested selects to include in the view. sql-expressions: Can only have at most one of `forEach` or `forEachOrNull`. ele-1: All FHIR elements must have a @value or children
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
column		0..*	BackboneElement	A column to be produced in the resulting table. ele-1: All FHIR elements must have a @value or children
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
path		1..1	string	FHIRPath expression that creates a column and defines its content
name	C	1..1	string	Column name produced in the output sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
description		0..1	markdown	Description of the column
collection		0..1	boolean	Indicates whether the column may have multiple values.
type		0..1	uri	A FHIR StructureDefinition URI for the column's type.
tag		0..*	BackboneElement	Additional metadata describing the column ele-1: All FHIR elements must have a @value or children
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
name		1..1	string	Name of tag
value		1..1	string	Value of tag
select		0..*	See select	Nested select relative to a parent expression.
(Choice of one)		0..1
forEach		0..1	string	A FHIRPath expression to retrieve the parent element(s) used in the containing select. The default is effectively `$this`.
forEachOrNull		0..1	string	Same as forEach, but will produce a row with null values if the collection is empty.
unionAll		0..*	See select	Creates a union of all rows in the given selection structures.
where		0..*	BackboneElement	A series of zero or more FHIRPath constraints to filter resources for the view. ele-1: All FHIR elements must have a @value or children
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
path		1..1	string	A FHIRPath expression defining a filter condition
description		0..1	string	A human-readable description of the above where constraint.
Documentation for this format

Terminology Bindings

Path	Conformance	ValueSet	URI
ViewDefinition.language	required	AllLanguages http://hl7.org/fhir/ValueSet/all-languages|5.0.0 from the FHIR Standard
ViewDefinition.versionAlgorithm[x]	extensible	VersionAlgorithm http://hl7.org/fhir/ValueSet/version-algorithm from the FHIR Standard
ViewDefinition.status	required	PublicationStatus http://hl7.org/fhir/ValueSet/publication-status|5.0.0 from the FHIR Standard
ViewDefinition.jurisdiction	extensible	JurisdictionValueSet http://hl7.org/fhir/ValueSet/jurisdiction from the FHIR Standard
ViewDefinition.resource	required	ResourceType http://hl7.org/fhir/ValueSet/resource-types from the FHIR Standard
ViewDefinition.fhirVersion	required	FHIRVersion http://hl7.org/fhir/ValueSet/FHIR-version from the FHIR Standard

Constraints

Id	Grade	Path(s)	Details	Requirements
cnl-0	warning	ViewDefinition	Name should be usable as an identifier for the module by machine processing applications such as code generation : name.exists() implies name.matches('^[A-Z]([A-Za-z0-9_]){1,254}$')
cnl-1	warning	ViewDefinition.url	URL should not contain | or # - these characters make processing canonical references problematic : exists() implies matches('^[^|# ]+$')
dom-2	error	ViewDefinition	If the resource is contained in another resource, it SHALL NOT contain nested Resources : contained.contained.empty()
dom-3	error	ViewDefinition	If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource : contained.where((('#'+id in (%resource.descendants().reference | %resource.descendants().ofType(canonical) | %resource.descendants().ofType(uri) | %resource.descendants().ofType(url))) or descendants().where(reference = '#').exists() or descendants().where(ofType(canonical) = '#').exists() or descendants().where(ofType(canonical) = '#').exists()).not()).trace('unmatched', id).empty()
dom-4	error	ViewDefinition	If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated : contained.meta.versionId.empty() and contained.meta.lastUpdated.empty()
dom-5	error	ViewDefinition	If a resource is contained in another resource, it SHALL NOT have a security label : contained.meta.security.empty()
dom-6	best practice	ViewDefinition	A resource should have narrative for robust management : text.`div`.exists()
ele-1	error	**ALL** elements	All FHIR elements must have a @value or children : hasValue() or (children().count() > id.count())
ext-1	error	**ALL** extensions	Must have either extensions or value[x], not both : extension.exists() != value.exists()
sql-expressions	error	ViewDefinition.select	Can only have at most one of `forEach` or `forEachOrNull`. : (forEach | forEachOrNull).count() <= 1
sql-name	error	ViewDefinition.name, ViewDefinition.constant.name, ViewDefinition.select.column.name	Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases. : empty() or matches('^[A-Za-z][A-Za-z0-9_]*$')

This structure is derived from CanonicalResource

Name	Flags	Card.	Type	Description & Constraints
ViewDefinition		1..1	CanonicalResource	Elements defined in Ancestors:id, meta, implicitRules, language, text, contained, extension, modifierExtension, url, identifier, version, versionAlgorithm[x], name, title, status, experimental, date, publisher, contact, description, useContext, jurisdiction, purpose, copyright, copyrightLabel View Definition
name	C	0..1	string	Name for this {{title}} (computer friendly) sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
resource		1..1	code	FHIR resource for the ViewDefinition Binding: ResourceType (required)
profile		0..*	canonical(StructureDefinition)	FHIR profiles that this view definition was intended to be executed against
fhirVersion		0..*	code	FHIR version(s) of the resource for the ViewDefinition Binding: FHIRVersion (required)
constant		0..*	BackboneElement	Constant that can be used in FHIRPath expressions
name	C	1..1	string	Name of constant (referred to in FHIRPath as %[name]) sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
value[x]		1..1		Value of constant
valueBase64Binary			base64Binary
valueBoolean			boolean
valueCanonical			canonical(Any)
valueCode			code
valueDate			date
valueDateTime			dateTime
valueDecimal			decimal
valueId			id
valueInstant			instant
valueInteger			integer
valueInteger64			integer64
valueOid			oid
valueString			string
valuePositiveInt			positiveInt
valueTime			time
valueUnsignedInt			unsignedInt
valueUri			uri
valueUrl			url
valueUuid			uuid
select	C	1..*	BackboneElement	A collection of columns and nested selects to include in the view. sql-expressions: Can only have at most one of `forEach` or `forEachOrNull`.
column		0..*	BackboneElement	A column to be produced in the resulting table.
path		1..1	string	FHIRPath expression that creates a column and defines its content
name	C	1..1	string	Column name produced in the output sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
description		0..1	markdown	Description of the column
collection		0..1	boolean	Indicates whether the column may have multiple values.
type		0..1	uri	A FHIR StructureDefinition URI for the column's type.
tag		0..*	BackboneElement	Additional metadata describing the column
name		1..1	string	Name of tag
value		1..1	string	Value of tag
select		0..*	See select	Nested select relative to a parent expression.
(Choice of one)		0..1
forEach		0..1	string	A FHIRPath expression to retrieve the parent element(s) used in the containing select. The default is effectively `$this`.
forEachOrNull		0..1	string	Same as forEach, but will produce a row with null values if the collection is empty.
unionAll		0..*	See select	Creates a union of all rows in the given selection structures.
where		0..*	BackboneElement	A series of zero or more FHIRPath constraints to filter resources for the view.
path		1..1	string	A FHIRPath expression defining a filter condition
description		0..1	string	A human-readable description of the above where constraint.
Documentation for this format

Terminology Bindings (Differential)

Path	Conformance	ValueSet	URI
ViewDefinition.resource	required	ResourceType http://hl7.org/fhir/ValueSet/resource-types from the FHIR Standard
ViewDefinition.fhirVersion	required	FHIRVersion http://hl7.org/fhir/ValueSet/FHIR-version from the FHIR Standard

Constraints

Id	Grade	Path(s)	Details	Requirements
sql-expressions	error	ViewDefinition.select	Can only have at most one of `forEach` or `forEachOrNull`. : (forEach | forEachOrNull).count() <= 1
sql-name	error	ViewDefinition.name, ViewDefinition.constant.name, ViewDefinition.select.column.name	Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases. : empty() or matches('^[A-Za-z][A-Za-z0-9_]*$')

Name	Flags	Card.	Type	Description & Constraints
ViewDefinition	C	1..1	CanonicalResource	Elements defined in Ancestors:id, meta, implicitRules, language, text, contained, extension, modifierExtension, url, identifier, version, versionAlgorithm[x], name, title, status, experimental, date, publisher, contact, description, useContext, jurisdiction, purpose, copyright, copyrightLabel View Definition
id	Σ	0..1	id	Logical id of this artifact
meta	Σ	0..1	Meta	Metadata about the resource
implicitRules	?!Σ	0..1	uri	A set of rules under which this content was created
language		0..1	code	Language of the resource content Binding: AllLanguages (required): IETF language tag for a human language Additional Bindings Purpose CommonLanguages Starter Set
text		0..1	Narrative	Text summary of the resource, for human interpretation
contained		0..*	Resource	Contained, inline Resources
extension		0..*	Extension	Additional content defined by implementations
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored
url	ΣC	0..1	uri	Canonical identifier for this {{title}}, represented as an absolute URI (globally unique)
identifier	Σ	0..*	Identifier	Additional identifier for the {{title}}
version	Σ	0..1	string	Business version of the {{title}}
versionAlgorithm[x]	Σ	0..1		How to compare versions Binding: VersionAlgorithm (extensible)
versionAlgorithmString			string
versionAlgorithmCoding			Coding
name	ΣC	0..1	string	Name for this {{title}} (computer friendly) sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
title	Σ	0..1	string	Name for this {{title}} (human friendly)
status	?!Σ	1..1	code	draft | active | retired | unknown Binding: PublicationStatus (required): The lifecycle status of an artifact.
experimental	Σ	0..1	boolean	For testing purposes, not real usage
date	Σ	0..1	dateTime	Date last changed
publisher	Σ	0..1	string	Name of the publisher/steward (organization or individual)
contact	Σ	0..*	ContactDetail	Contact details for the publisher
description		0..1	markdown	Natural language description of the {{title}}
useContext	Σ	0..*	UsageContext	The context that the content is intended to support
jurisdiction	Σ	0..*	CodeableConcept	Intended jurisdiction for {{title}} (if applicable) Binding: JurisdictionValueSet (extensible): Countries and regions within which this artifact is targeted for use.
purpose		0..1	markdown	Why this {{title}} is defined
copyright		0..1	markdown	Use and/or publishing restrictions
copyrightLabel		0..1	string	Copyright holder and year(s)
resource		1..1	code	FHIR resource for the ViewDefinition Binding: ResourceType (required)
profile		0..*	canonical(StructureDefinition)	FHIR profiles that this view definition was intended to be executed against
fhirVersion		0..*	code	FHIR version(s) of the resource for the ViewDefinition Binding: FHIRVersion (required)
constant		0..*	BackboneElement	Constant that can be used in FHIRPath expressions
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized
name	C	1..1	string	Name of constant (referred to in FHIRPath as %[name]) sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
value[x]		1..1		Value of constant
valueBase64Binary			base64Binary
valueBoolean			boolean
valueCanonical			canonical(Any)
valueCode			code
valueDate			date
valueDateTime			dateTime
valueDecimal			decimal
valueId			id
valueInstant			instant
valueInteger			integer
valueInteger64			integer64
valueOid			oid
valueString			string
valuePositiveInt			positiveInt
valueTime			time
valueUnsignedInt			unsignedInt
valueUri			uri
valueUrl			url
valueUuid			uuid
select	C	1..*	BackboneElement	A collection of columns and nested selects to include in the view. sql-expressions: Can only have at most one of `forEach` or `forEachOrNull`.
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized
column		0..*	BackboneElement	A column to be produced in the resulting table.
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized
path		1..1	string	FHIRPath expression that creates a column and defines its content
name	C	1..1	string	Column name produced in the output sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
description		0..1	markdown	Description of the column
collection		0..1	boolean	Indicates whether the column may have multiple values.
type		0..1	uri	A FHIR StructureDefinition URI for the column's type.
tag		0..*	BackboneElement	Additional metadata describing the column
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized
name		1..1	string	Name of tag
value		1..1	string	Value of tag
select		0..*	See select	Nested select relative to a parent expression.
(Choice of one)		0..1
forEach		0..1	string	A FHIRPath expression to retrieve the parent element(s) used in the containing select. The default is effectively `$this`.
forEachOrNull		0..1	string	Same as forEach, but will produce a row with null values if the collection is empty.
unionAll		0..*	See select	Creates a union of all rows in the given selection structures.
where		0..*	BackboneElement	A series of zero or more FHIRPath constraints to filter resources for the view.
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized
path		1..1	string	A FHIRPath expression defining a filter condition
description		0..1	string	A human-readable description of the above where constraint.
Documentation for this format

Terminology Bindings

Path	Conformance	ValueSet	URI
ViewDefinition.language	required	AllLanguages http://hl7.org/fhir/ValueSet/all-languages|5.0.0 from the FHIR Standard
ViewDefinition.versionAlgorithm[x]	extensible	VersionAlgorithm http://hl7.org/fhir/ValueSet/version-algorithm from the FHIR Standard
ViewDefinition.status	required	PublicationStatus http://hl7.org/fhir/ValueSet/publication-status|5.0.0 from the FHIR Standard
ViewDefinition.jurisdiction	extensible	JurisdictionValueSet http://hl7.org/fhir/ValueSet/jurisdiction from the FHIR Standard
ViewDefinition.resource	required	ResourceType http://hl7.org/fhir/ValueSet/resource-types from the FHIR Standard
ViewDefinition.fhirVersion	required	FHIRVersion http://hl7.org/fhir/ValueSet/FHIR-version from the FHIR Standard

Constraints

Id	Grade	Path(s)	Details	Requirements
cnl-0	warning	ViewDefinition	Name should be usable as an identifier for the module by machine processing applications such as code generation : name.exists() implies name.matches('^[A-Z]([A-Za-z0-9_]){1,254}$')
cnl-1	warning	ViewDefinition.url	URL should not contain | or # - these characters make processing canonical references problematic : exists() implies matches('^[^|# ]+$')
dom-2	error	ViewDefinition	If the resource is contained in another resource, it SHALL NOT contain nested Resources : contained.contained.empty()
dom-3	error	ViewDefinition	If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource : contained.where((('#'+id in (%resource.descendants().reference | %resource.descendants().ofType(canonical) | %resource.descendants().ofType(uri) | %resource.descendants().ofType(url))) or descendants().where(reference = '#').exists() or descendants().where(ofType(canonical) = '#').exists() or descendants().where(ofType(canonical) = '#').exists()).not()).trace('unmatched', id).empty()
dom-4	error	ViewDefinition	If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated : contained.meta.versionId.empty() and contained.meta.lastUpdated.empty()
dom-5	error	ViewDefinition	If a resource is contained in another resource, it SHALL NOT have a security label : contained.meta.security.empty()
dom-6	best practice	ViewDefinition	A resource should have narrative for robust management : text.`div`.exists()
ele-1	error	**ALL** elements	All FHIR elements must have a @value or children : hasValue() or (children().count() > id.count())
ext-1	error	**ALL** extensions	Must have either extensions or value[x], not both : extension.exists() != value.exists()
sql-expressions	error	ViewDefinition.select	Can only have at most one of `forEach` or `forEachOrNull`. : (forEach | forEachOrNull).count() <= 1
sql-name	error	ViewDefinition.name, ViewDefinition.constant.name, ViewDefinition.select.column.name	Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases. : empty() or matches('^[A-Za-z][A-Za-z0-9_]*$')

Key Elements View

Name	Flags	Card.	Type	Description & Constraints
ViewDefinition	C	1..1	CanonicalResource	Elements defined in Ancestors:id, meta, implicitRules, language, text, contained, extension, modifierExtension, url, identifier, version, versionAlgorithm[x], name, title, status, experimental, date, publisher, contact, description, useContext, jurisdiction, purpose, copyright, copyrightLabel View Definition cnl-0: Name should be usable as an identifier for the module by machine processing applications such as code generation dom-2: If the resource is contained in another resource, it SHALL NOT contain nested Resources dom-3: If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource dom-4: If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated dom-5: If a resource is contained in another resource, it SHALL NOT have a security label dom-6: A resource should have narrative for robust management
id	Σ	0..1	id	Logical id of this artifact
meta	Σ	0..1	Meta	Metadata about the resource ele-1: All FHIR elements must have a @value or children
implicitRules	?!Σ	0..1	uri	A set of rules under which this content was created ele-1: All FHIR elements must have a @value or children
language		0..1	code	Language of the resource content Binding: AllLanguages (required): IETF language tag for a human language Additional Bindings Purpose CommonLanguages Starter Set ele-1: All FHIR elements must have a @value or children
text		0..1	Narrative	Text summary of the resource, for human interpretation ele-1: All FHIR elements must have a @value or children
contained		0..*	Resource	Contained, inline Resources
extension		0..*	Extension	Additional content defined by implementations ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
url	ΣC	0..1	uri	Canonical identifier for this {{title}}, represented as an absolute URI (globally unique) cnl-1: URL should not contain | or # - these characters make processing canonical references problematic ele-1: All FHIR elements must have a @value or children
identifier	Σ	0..*	Identifier	Additional identifier for the {{title}} ele-1: All FHIR elements must have a @value or children
version	Σ	0..1	string	Business version of the {{title}} ele-1: All FHIR elements must have a @value or children
versionAlgorithm[x]	Σ	0..1		How to compare versions Binding: VersionAlgorithm (extensible) ele-1: All FHIR elements must have a @value or children
versionAlgorithmString			string
versionAlgorithmCoding			Coding
name	ΣC	0..1	string	Name for this {{title}} (computer friendly) ele-1: All FHIR elements must have a @value or children sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
title	Σ	0..1	string	Name for this {{title}} (human friendly) ele-1: All FHIR elements must have a @value or children
status	?!Σ	1..1	code	draft | active | retired | unknown Binding: PublicationStatus (required): The lifecycle status of an artifact. ele-1: All FHIR elements must have a @value or children
experimental	Σ	0..1	boolean	For testing purposes, not real usage ele-1: All FHIR elements must have a @value or children
date	Σ	0..1	dateTime	Date last changed ele-1: All FHIR elements must have a @value or children
publisher	Σ	0..1	string	Name of the publisher/steward (organization or individual) ele-1: All FHIR elements must have a @value or children
contact	Σ	0..*	ContactDetail	Contact details for the publisher ele-1: All FHIR elements must have a @value or children
description		0..1	markdown	Natural language description of the {{title}} ele-1: All FHIR elements must have a @value or children
useContext	Σ	0..*	UsageContext	The context that the content is intended to support ele-1: All FHIR elements must have a @value or children
jurisdiction	Σ	0..*	CodeableConcept	Intended jurisdiction for {{title}} (if applicable) Binding: JurisdictionValueSet (extensible): Countries and regions within which this artifact is targeted for use. ele-1: All FHIR elements must have a @value or children
purpose		0..1	markdown	Why this {{title}} is defined ele-1: All FHIR elements must have a @value or children
copyright		0..1	markdown	Use and/or publishing restrictions ele-1: All FHIR elements must have a @value or children
copyrightLabel		0..1	string	Copyright holder and year(s) ele-1: All FHIR elements must have a @value or children
resource		1..1	code	FHIR resource for the ViewDefinition Binding: ResourceType (required)
profile		0..*	canonical(StructureDefinition)	FHIR profiles that this view definition was intended to be executed against
fhirVersion		0..*	code	FHIR version(s) of the resource for the ViewDefinition Binding: FHIRVersion (required)
constant		0..*	BackboneElement	Constant that can be used in FHIRPath expressions ele-1: All FHIR elements must have a @value or children
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
name	C	1..1	string	Name of constant (referred to in FHIRPath as %[name]) sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
value[x]		1..1		Value of constant
valueBase64Binary			base64Binary
valueBoolean			boolean
valueCanonical			canonical(Any)
valueCode			code
valueDate			date
valueDateTime			dateTime
valueDecimal			decimal
valueId			id
valueInstant			instant
valueInteger			integer
valueInteger64			integer64
valueOid			oid
valueString			string
valuePositiveInt			positiveInt
valueTime			time
valueUnsignedInt			unsignedInt
valueUri			uri
valueUrl			url
valueUuid			uuid
select	C	1..*	BackboneElement	A collection of columns and nested selects to include in the view. sql-expressions: Can only have at most one of `forEach` or `forEachOrNull`. ele-1: All FHIR elements must have a @value or children
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
column		0..*	BackboneElement	A column to be produced in the resulting table. ele-1: All FHIR elements must have a @value or children
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
path		1..1	string	FHIRPath expression that creates a column and defines its content
name	C	1..1	string	Column name produced in the output sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
description		0..1	markdown	Description of the column
collection		0..1	boolean	Indicates whether the column may have multiple values.
type		0..1	uri	A FHIR StructureDefinition URI for the column's type.
tag		0..*	BackboneElement	Additional metadata describing the column ele-1: All FHIR elements must have a @value or children
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
name		1..1	string	Name of tag
value		1..1	string	Value of tag
select		0..*	See select	Nested select relative to a parent expression.
(Choice of one)		0..1
forEach		0..1	string	A FHIRPath expression to retrieve the parent element(s) used in the containing select. The default is effectively `$this`.
forEachOrNull		0..1	string	Same as forEach, but will produce a row with null values if the collection is empty.
unionAll		0..*	See select	Creates a union of all rows in the given selection structures.
where		0..*	BackboneElement	A series of zero or more FHIRPath constraints to filter resources for the view. ele-1: All FHIR elements must have a @value or children
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized ele-1: All FHIR elements must have a @value or children ext-1: Must have either extensions or value[x], not both
path		1..1	string	A FHIRPath expression defining a filter condition
description		0..1	string	A human-readable description of the above where constraint.
Documentation for this format

Terminology Bindings

Path	Conformance	ValueSet	URI
ViewDefinition.language	required	AllLanguages http://hl7.org/fhir/ValueSet/all-languages|5.0.0 from the FHIR Standard
ViewDefinition.versionAlgorithm[x]	extensible	VersionAlgorithm http://hl7.org/fhir/ValueSet/version-algorithm from the FHIR Standard
ViewDefinition.status	required	PublicationStatus http://hl7.org/fhir/ValueSet/publication-status|5.0.0 from the FHIR Standard
ViewDefinition.jurisdiction	extensible	JurisdictionValueSet http://hl7.org/fhir/ValueSet/jurisdiction from the FHIR Standard
ViewDefinition.resource	required	ResourceType http://hl7.org/fhir/ValueSet/resource-types from the FHIR Standard
ViewDefinition.fhirVersion	required	FHIRVersion http://hl7.org/fhir/ValueSet/FHIR-version from the FHIR Standard

Constraints

Id	Grade	Path(s)	Details	Requirements
cnl-0	warning	ViewDefinition	Name should be usable as an identifier for the module by machine processing applications such as code generation : name.exists() implies name.matches('^[A-Z]([A-Za-z0-9_]){1,254}$')
cnl-1	warning	ViewDefinition.url	URL should not contain | or # - these characters make processing canonical references problematic : exists() implies matches('^[^|# ]+$')
dom-2	error	ViewDefinition	If the resource is contained in another resource, it SHALL NOT contain nested Resources : contained.contained.empty()
dom-3	error	ViewDefinition	If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource : contained.where((('#'+id in (%resource.descendants().reference | %resource.descendants().ofType(canonical) | %resource.descendants().ofType(uri) | %resource.descendants().ofType(url))) or descendants().where(reference = '#').exists() or descendants().where(ofType(canonical) = '#').exists() or descendants().where(ofType(canonical) = '#').exists()).not()).trace('unmatched', id).empty()
dom-4	error	ViewDefinition	If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated : contained.meta.versionId.empty() and contained.meta.lastUpdated.empty()
dom-5	error	ViewDefinition	If a resource is contained in another resource, it SHALL NOT have a security label : contained.meta.security.empty()
dom-6	best practice	ViewDefinition	A resource should have narrative for robust management : text.`div`.exists()
ele-1	error	**ALL** elements	All FHIR elements must have a @value or children : hasValue() or (children().count() > id.count())
ext-1	error	**ALL** extensions	Must have either extensions or value[x], not both : extension.exists() != value.exists()
sql-expressions	error	ViewDefinition.select	Can only have at most one of `forEach` or `forEachOrNull`. : (forEach | forEachOrNull).count() <= 1
sql-name	error	ViewDefinition.name, ViewDefinition.constant.name, ViewDefinition.select.column.name	Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases. : empty() or matches('^[A-Za-z][A-Za-z0-9_]*$')

Differential View

This structure is derived from CanonicalResource

Name	Flags	Card.	Type	Description & Constraints
ViewDefinition		1..1	CanonicalResource	Elements defined in Ancestors:id, meta, implicitRules, language, text, contained, extension, modifierExtension, url, identifier, version, versionAlgorithm[x], name, title, status, experimental, date, publisher, contact, description, useContext, jurisdiction, purpose, copyright, copyrightLabel View Definition
name	C	0..1	string	Name for this {{title}} (computer friendly) sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
resource		1..1	code	FHIR resource for the ViewDefinition Binding: ResourceType (required)
profile		0..*	canonical(StructureDefinition)	FHIR profiles that this view definition was intended to be executed against
fhirVersion		0..*	code	FHIR version(s) of the resource for the ViewDefinition Binding: FHIRVersion (required)
constant		0..*	BackboneElement	Constant that can be used in FHIRPath expressions
name	C	1..1	string	Name of constant (referred to in FHIRPath as %[name]) sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
value[x]		1..1		Value of constant
valueBase64Binary			base64Binary
valueBoolean			boolean
valueCanonical			canonical(Any)
valueCode			code
valueDate			date
valueDateTime			dateTime
valueDecimal			decimal
valueId			id
valueInstant			instant
valueInteger			integer
valueInteger64			integer64
valueOid			oid
valueString			string
valuePositiveInt			positiveInt
valueTime			time
valueUnsignedInt			unsignedInt
valueUri			uri
valueUrl			url
valueUuid			uuid
select	C	1..*	BackboneElement	A collection of columns and nested selects to include in the view. sql-expressions: Can only have at most one of `forEach` or `forEachOrNull`.
column		0..*	BackboneElement	A column to be produced in the resulting table.
path		1..1	string	FHIRPath expression that creates a column and defines its content
name	C	1..1	string	Column name produced in the output sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
description		0..1	markdown	Description of the column
collection		0..1	boolean	Indicates whether the column may have multiple values.
type		0..1	uri	A FHIR StructureDefinition URI for the column's type.
tag		0..*	BackboneElement	Additional metadata describing the column
name		1..1	string	Name of tag
value		1..1	string	Value of tag
select		0..*	See select	Nested select relative to a parent expression.
(Choice of one)		0..1
forEach		0..1	string	A FHIRPath expression to retrieve the parent element(s) used in the containing select. The default is effectively `$this`.
forEachOrNull		0..1	string	Same as forEach, but will produce a row with null values if the collection is empty.
unionAll		0..*	See select	Creates a union of all rows in the given selection structures.
where		0..*	BackboneElement	A series of zero or more FHIRPath constraints to filter resources for the view.
path		1..1	string	A FHIRPath expression defining a filter condition
description		0..1	string	A human-readable description of the above where constraint.
Documentation for this format

Terminology Bindings (Differential)

Path	Conformance	ValueSet	URI
ViewDefinition.resource	required	ResourceType http://hl7.org/fhir/ValueSet/resource-types from the FHIR Standard
ViewDefinition.fhirVersion	required	FHIRVersion http://hl7.org/fhir/ValueSet/FHIR-version from the FHIR Standard

Constraints

Id	Grade	Path(s)	Details	Requirements
sql-expressions	error	ViewDefinition.select	Can only have at most one of `forEach` or `forEachOrNull`. : (forEach | forEachOrNull).count() <= 1
sql-name	error	ViewDefinition.name, ViewDefinition.constant.name, ViewDefinition.select.column.name	Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases. : empty() or matches('^[A-Za-z][A-Za-z0-9_]*$')

Snapshot View

Name	Flags	Card.	Type	Description & Constraints
ViewDefinition	C	1..1	CanonicalResource	Elements defined in Ancestors:id, meta, implicitRules, language, text, contained, extension, modifierExtension, url, identifier, version, versionAlgorithm[x], name, title, status, experimental, date, publisher, contact, description, useContext, jurisdiction, purpose, copyright, copyrightLabel View Definition
id	Σ	0..1	id	Logical id of this artifact
meta	Σ	0..1	Meta	Metadata about the resource
implicitRules	?!Σ	0..1	uri	A set of rules under which this content was created
language		0..1	code	Language of the resource content Binding: AllLanguages (required): IETF language tag for a human language Additional Bindings Purpose CommonLanguages Starter Set
text		0..1	Narrative	Text summary of the resource, for human interpretation
contained		0..*	Resource	Contained, inline Resources
extension		0..*	Extension	Additional content defined by implementations
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored
url	ΣC	0..1	uri	Canonical identifier for this {{title}}, represented as an absolute URI (globally unique)
identifier	Σ	0..*	Identifier	Additional identifier for the {{title}}
version	Σ	0..1	string	Business version of the {{title}}
versionAlgorithm[x]	Σ	0..1		How to compare versions Binding: VersionAlgorithm (extensible)
versionAlgorithmString			string
versionAlgorithmCoding			Coding
name	ΣC	0..1	string	Name for this {{title}} (computer friendly) sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
title	Σ	0..1	string	Name for this {{title}} (human friendly)
status	?!Σ	1..1	code	draft | active | retired | unknown Binding: PublicationStatus (required): The lifecycle status of an artifact.
experimental	Σ	0..1	boolean	For testing purposes, not real usage
date	Σ	0..1	dateTime	Date last changed
publisher	Σ	0..1	string	Name of the publisher/steward (organization or individual)
contact	Σ	0..*	ContactDetail	Contact details for the publisher
description		0..1	markdown	Natural language description of the {{title}}
useContext	Σ	0..*	UsageContext	The context that the content is intended to support
jurisdiction	Σ	0..*	CodeableConcept	Intended jurisdiction for {{title}} (if applicable) Binding: JurisdictionValueSet (extensible): Countries and regions within which this artifact is targeted for use.
purpose		0..1	markdown	Why this {{title}} is defined
copyright		0..1	markdown	Use and/or publishing restrictions
copyrightLabel		0..1	string	Copyright holder and year(s)
resource		1..1	code	FHIR resource for the ViewDefinition Binding: ResourceType (required)
profile		0..*	canonical(StructureDefinition)	FHIR profiles that this view definition was intended to be executed against
fhirVersion		0..*	code	FHIR version(s) of the resource for the ViewDefinition Binding: FHIRVersion (required)
constant		0..*	BackboneElement	Constant that can be used in FHIRPath expressions
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized
name	C	1..1	string	Name of constant (referred to in FHIRPath as %[name]) sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
value[x]		1..1		Value of constant
valueBase64Binary			base64Binary
valueBoolean			boolean
valueCanonical			canonical(Any)
valueCode			code
valueDate			date
valueDateTime			dateTime
valueDecimal			decimal
valueId			id
valueInstant			instant
valueInteger			integer
valueInteger64			integer64
valueOid			oid
valueString			string
valuePositiveInt			positiveInt
valueTime			time
valueUnsignedInt			unsignedInt
valueUri			uri
valueUrl			url
valueUuid			uuid
select	C	1..*	BackboneElement	A collection of columns and nested selects to include in the view. sql-expressions: Can only have at most one of `forEach` or `forEachOrNull`.
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized
column		0..*	BackboneElement	A column to be produced in the resulting table.
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized
path		1..1	string	FHIRPath expression that creates a column and defines its content
name	C	1..1	string	Column name produced in the output sql-name: Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases.
description		0..1	markdown	Description of the column
collection		0..1	boolean	Indicates whether the column may have multiple values.
type		0..1	uri	A FHIR StructureDefinition URI for the column's type.
tag		0..*	BackboneElement	Additional metadata describing the column
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized
name		1..1	string	Name of tag
value		1..1	string	Value of tag
select		0..*	See select	Nested select relative to a parent expression.
(Choice of one)		0..1
forEach		0..1	string	A FHIRPath expression to retrieve the parent element(s) used in the containing select. The default is effectively `$this`.
forEachOrNull		0..1	string	Same as forEach, but will produce a row with null values if the collection is empty.
unionAll		0..*	See select	Creates a union of all rows in the given selection structures.
where		0..*	BackboneElement	A series of zero or more FHIRPath constraints to filter resources for the view.
@id		0..1	id	Unique id for inter-element referencing
extension		0..*	Extension	Additional content defined by implementations Slice: Unordered, Open by value:url
modifierExtension	?!Σ	0..*	Extension	Extensions that cannot be ignored even if unrecognized
path		1..1	string	A FHIRPath expression defining a filter condition
description		0..1	string	A human-readable description of the above where constraint.
Documentation for this format

Terminology Bindings

Path	Conformance	ValueSet	URI
ViewDefinition.language	required	AllLanguages http://hl7.org/fhir/ValueSet/all-languages|5.0.0 from the FHIR Standard
ViewDefinition.versionAlgorithm[x]	extensible	VersionAlgorithm http://hl7.org/fhir/ValueSet/version-algorithm from the FHIR Standard
ViewDefinition.status	required	PublicationStatus http://hl7.org/fhir/ValueSet/publication-status|5.0.0 from the FHIR Standard
ViewDefinition.jurisdiction	extensible	JurisdictionValueSet http://hl7.org/fhir/ValueSet/jurisdiction from the FHIR Standard
ViewDefinition.resource	required	ResourceType http://hl7.org/fhir/ValueSet/resource-types from the FHIR Standard
ViewDefinition.fhirVersion	required	FHIRVersion http://hl7.org/fhir/ValueSet/FHIR-version from the FHIR Standard

Constraints

Id	Grade	Path(s)	Details	Requirements
cnl-0	warning	ViewDefinition	Name should be usable as an identifier for the module by machine processing applications such as code generation : name.exists() implies name.matches('^[A-Z]([A-Za-z0-9_]){1,254}$')
cnl-1	warning	ViewDefinition.url	URL should not contain | or # - these characters make processing canonical references problematic : exists() implies matches('^[^|# ]+$')
dom-2	error	ViewDefinition	If the resource is contained in another resource, it SHALL NOT contain nested Resources : contained.contained.empty()
dom-3	error	ViewDefinition	If the resource is contained in another resource, it SHALL be referred to from elsewhere in the resource or SHALL refer to the containing resource : contained.where((('#'+id in (%resource.descendants().reference | %resource.descendants().ofType(canonical) | %resource.descendants().ofType(uri) | %resource.descendants().ofType(url))) or descendants().where(reference = '#').exists() or descendants().where(ofType(canonical) = '#').exists() or descendants().where(ofType(canonical) = '#').exists()).not()).trace('unmatched', id).empty()
dom-4	error	ViewDefinition	If a resource is contained in another resource, it SHALL NOT have a meta.versionId or a meta.lastUpdated : contained.meta.versionId.empty() and contained.meta.lastUpdated.empty()
dom-5	error	ViewDefinition	If a resource is contained in another resource, it SHALL NOT have a security label : contained.meta.security.empty()
dom-6	best practice	ViewDefinition	A resource should have narrative for robust management : text.`div`.exists()
ele-1	error	**ALL** elements	All FHIR elements must have a @value or children : hasValue() or (children().count() > id.count())
ext-1	error	**ALL** extensions	Must have either extensions or value[x], not both : extension.exists() != value.exists()
sql-expressions	error	ViewDefinition.select	Can only have at most one of `forEach` or `forEachOrNull`. : (forEach | forEachOrNull).count() <= 1
sql-name	error	ViewDefinition.name, ViewDefinition.constant.name, ViewDefinition.select.column.name	Name is limited to letters, numbers, or underscores and cannot start with an underscore -- i.e. with a regular expression of: ^[A-Za-z][A-Za-z0-9_]*$ This makes it usable as table names in a wide variety of databases. : empty() or matches('^[A-Za-z][A-Za-z0-9_]*$')

This structure is derived from CanonicalResource

Summary

Mandatory: 0 element(9 nested mandatory elements)

FHIRPath Functionality

Columns within a view are defined using the FHIRPath language. FHIRPath contains a large number of functions and syntax constructs - not all of these are required to be implemented within a SQL on FHIR view runner.

View runner implementations MUST support the following required additional FHIRPath functions. In addition to this, runners SHOULD implement the FHIRPath subset defined in the Shareable View Definition profile if the intent is for the runner to be able to execute shared view definitions.

Required Additional Functions

All View Runners must implement these functions that extend the FHIRPath specification. Despite not being in the FHIRPath specification, they are necessary in the context of defining views:

• getResourceKey function
• getReferenceKey function

getResourceKey() : KeyType

This is invoked at the root of a FHIR Resource and returns an opaque value to be used as the primary key for the row associated with the resource. In many cases the value may just be the resource id, but exceptions are described below.

This function is used in tandem with getReferenceKey, which returns an equal value from references that point to this resource.

The returned KeyType is implementation dependent, but must be a FHIR primitive type that can be used for efficient joins in the system's underlying data storage. Integers, strings, UUIDs, and other primitive types may be appropriate.

See the Joins with Resource and Reference Keys section below for details.

getReferenceKey([resource: type specifier]) : KeyType

This is invoked on Reference elements and returns an opaque value that represents the database key of the row being referenced. The value returned must be equal to the getResourceKey value returned on the resource itself.

Users may pass an optional resource type (e.g., Patient or Observation) to indicate the expected type that the reference should point to. The getReferenceKey function will return an empty collection (effectively null since FHIRPath always returns collections) if the reference is not of the expected type. For example, Observation.subject.getReferenceKey(Patient) would return a row key if the subject is a Patient, or the empty collection ( i.e., {}) if it is not.

The returned KeyType is implementation dependent, but must be a FHIR primitive type that can be used for efficient joins in the systems underlying data storage. Integers, strings, UUIDs, and other primitive types may be appropriate.

The getReferenceKey function has both required and optional functionality:

• Implementations MUST support the relative literal form of reference ( e.g., Patient/123), and MAY support other types of references. If the implementation does not support the reference type, or is unable to resolve the reference, it MUST return the empty collection (i.e., {}).
• Implementations MAY generate a list of unprocessable references through query responses, logging or reporting. The details of how this information would be provided to the user is implementation specific.

See the Joins with Resource and Reference Keys section below for details.

Specifying a Select

A select specifies the content and names for the columns in the view. The content for each column is defined with a FHIRPath expression that returns a specific data element from the FHIR resources. More complex views can be specified to create resource or reference keys, unnest a collection of items returned by a FHIRPath expression, nest or concatenate the results from multiple selects, and so on.

Unnesting Semantics

It is often desirable to unroll the collection returned from a FHIRPath expression into a separate row for each item in the collection. This is done with forEach or forEachOrNull.

​For instance, each Patient resource can have multiple addresses, which users can expand into a separate patient_addresses table with one row per address. Each row would still have a patient_id field to know which patient that address row is associated with. You can see this in the PatientAddresses example, which unrolls addresses as described above.

forEach and forEachOrNull apply both to the columns within a select and any nested selects it contains. Therefore, the following selects will produce the same results:

"select": [{
  "forEach": "address",
  "column": [{"name": "zip", "path": "postalCode"}]
}]

"select": [{
  "forEach": "address",
  "select": [{"column": [{"name": "zip", "path": "postalCode"}]}]
}]

While a forEach is similar to an INNER JOIN supported by many SQL engines, a forEachOrNull is analogous to a LEFT OUTER JOIN. forEach will produce a row only if the FHIRPath expression returns one or more items in the collection. On the other hand, forEachOrNull will produce a row even if the FHIRPath expression returns an empty collection. With forEachOrNull, all columns will be included but, if nothing is returned by the forEachOrNull expression, the row produced will have null values.

To illustrate this, the following expression in a Patient view uses forEach, and will therefore return a row for each Patient resource only if the Patient resource has at least one Patient.address, similar to an INNER JOIN in SQL:

"select": [
  {
    "column": [{"name": "id", "path": "getResourceKey()"}]
  },
  {
    "forEach": "address",
    "select": [{"column": [{"name": "zip", "path": "postalCode"}]}]
  }
]

In contrast, this view with forEachOrNull will produce the id column for every Patient resource. If the Patient resource has no Patient.address, there will be a single row for the Patient resource and the zip column will contain null. For Patient resources with one or more Patient.address, the result will be identical to the expression above.

"select": [
  {
    "column": [{"name": "id", "path": "getResourceKey()"}]
  },
  {
    "forEachOrNull": "address",
    "select": [{"column": [{"name": "zip", "path": "postalCode"}]}]
  }
]

Multiple Select Expressions

A ViewDefinition may have multiple selects, which can be organized as siblings or in parent/child relationships. This is typically done as different selects may use different forEach or forEachOrNullexpressions to unroll different parts of the resources.

The multiple rows produced using forEach or forEachOrNull from a selectare joined to others with the following rules:

• Parent/child selects will repeat values from the parent select for each item in the child select.
• Sibling selects are effectively cross joined, where each row in each select is duplicated for every row in sibling selects.

The examples illustrate this behavior.

Unions

A select can have an optional unionAll, which contains a list of selects that are used to create a union. unionAll effectively concatenates the results of the nested selects that it contains, but without a guarantee that row ordering will be preserved. Each select contained in the unionAll must produce the same columns including their specified names and FHIR types.

"select": {
  "unionAll": [
    {
      "forEach": "address",
      "column": [
        {"path": "postalCode", "name": "zip"},
        {"path": "true", "name": "is_patient"}
      ]
    },
    {
      "forEach": "contact.address",
      "column": [
        {"path": "postalCode", "name": "zip"},
        {"path": "false", "name": "is_patient"}
      ]
    }
  ]
}