Release 5 Draft Ballot

This page is part of the FHIR Specification (v4.6.0: R5 Draft Ballot). The current version which supercedes this version is 5.0.0. For a full list of available versions, see the Directory of published versions . Page versions: R4B R4

Extension: expression

Vocabulary Work Group

Maturity Level: 1

Informative

Use Context: Any

URL for this extension:

http://hl7.org/fhir/StructureDefinition/valueset-expression

Status: draft. Extension maintained by: HL7

An expression that provides an alternative definition of the content of the value set (compose). There are two different ways to use this expression extension: If both an expression (this extension) and a compose element is present, the compose is understood to the make the same statement as the expression. If there is no compose, the expression is the only definition of the value set, and the value set can only be processed by a server that understands the expression syntax, the expression is computable.

Comment:

The expression may be a reference or the actual expression, and is expected to be in a computable format. Use the rules-text extension for a non-computable expression of the value set definition (compose).

Context of Use: Use on Element ID ValueSet

Summary

Name	Flags	Card.	Type	Description & Constraints
expression		0..1	Expression	URL = http://hl7.org/fhir/StructureDefinition/valueset-expression expression: An expression that provides an alternative definition of the content of the value set (compose). There are two different ways to use this expression extension: If both an expression (this extension) and a compose element is present, the compose is understood to the make the same statement as the expression. If there is no compose, the expression is the only definition of the value set, and the value set can only be processed by a server that understands the expression syntax, the expression is computable. Use on Element ID ValueSet
Documentation for this format

Full Structure

Name	Card.	Type	Description & Constraints
extension	0..1	Extension	URL = http://hl7.org/fhir/StructureDefinition/valueset-expression expression: An expression that provides an alternative definition of the content of the value set (compose). There are two different ways to use this expression extension: If both an expression (this extension) and a compose element is present, the compose is understood to the make the same statement as the expression. If there is no compose, the expression is the only definition of the value set, and the value set can only be processed by a server that understands the expression syntax, the expression is computable. Use on Element ID ValueSet
extension	0..0
url	1..1	uri	"http://hl7.org/fhir/StructureDefinition/valueset-expression"
value[x]	1..1	Expression	Value of extension
Documentation for this format

XML Template

<!-- expression -->

<extension xmlns="http://hl7.org/fhir"
     url="http://hl7.org/fhir/StructureDefinition/valueset-expression" >
  <!-- from Element: extension -->
 <valueExpression><!--  1..1 Expression Value of extension --></valueExpression>
</extension>

JSON Template

{ // expression
  // from Element: extension
    "extension" : [ //  sliced by value:url  in the specified order, Open ]
    "url" : "http://hl7.org/fhir/StructureDefinition/valueset-expression", // R! 
    "valueExpression" : { Expression } // C? R! Value of extension
  }

Summary

Name	Flags	Card.	Type	Description & Constraints
expression		0..1	Expression	URL = http://hl7.org/fhir/StructureDefinition/valueset-expression expression: An expression that provides an alternative definition of the content of the value set (compose). There are two different ways to use this expression extension: If both an expression (this extension) and a compose element is present, the compose is understood to the make the same statement as the expression. If there is no compose, the expression is the only definition of the value set, and the value set can only be processed by a server that understands the expression syntax, the expression is computable. Use on Element ID ValueSet
Documentation for this format

Full Structure

Name	Card.	Type	Description & Constraints
extension	0..1	Extension	URL = http://hl7.org/fhir/StructureDefinition/valueset-expression expression: An expression that provides an alternative definition of the content of the value set (compose). There are two different ways to use this expression extension: If both an expression (this extension) and a compose element is present, the compose is understood to the make the same statement as the expression. If there is no compose, the expression is the only definition of the value set, and the value set can only be processed by a server that understands the expression syntax, the expression is computable. Use on Element ID ValueSet
extension	0..0
url	1..1	uri	"http://hl7.org/fhir/StructureDefinition/valueset-expression"
value[x]	1..1	Expression	Value of extension
Documentation for this format

XML Template

<!-- expression -->

<extension xmlns="http://hl7.org/fhir"
     url="http://hl7.org/fhir/StructureDefinition/valueset-expression" >
  <!-- from Element: extension -->
 <valueExpression><!--  1..1 Expression Value of extension --></valueExpression>
</extension>

JSON Template

{ // expression
  // from Element: extension
    "extension" : [ //  sliced by value:url  in the specified order, Open ]
    "url" : "http://hl7.org/fhir/StructureDefinition/valueset-expression", // R! 
    "valueExpression" : { Expression } // C? R! Value of extension
  }

Constraints

ele-1: All FHIR elements must have a @value or children (xpath: @value|f:*|h:div)
ext-1: Must have either extensions or value[x], not both (xpath: exists(f:extension)!=exists(f:*[starts-with(local-name(.), 'value')]))
ele-1: On Extension.extension: All FHIR elements must have a @value or children (xpath on Extension.extension: @value|f:*|h:div)
ext-1: On Extension.extension: Must have either extensions or value[x], not both (xpath on Extension.extension: exists(f:extension)!=exists(f:*[starts-with(local-name(.), "value")]))
ele-1: On Extension.value[x]: All FHIR elements must have a @value or children (xpath on Extension.value[x]: @value|f:*|h:div)