---
type: "datatype"
title: "Expression"
datatype: "Expression"
---
# Expression

- [Datatypes](/datatypes)
- [Definitions](/datatypes-definitions#Expression)
- [Examples](/datatypes-examples#Expression)
- [Mappings](/datatypes-mappings#Expression)
- [Profiles](/datatypes-profiles#Expression)

## Elements

- **[Expression.description](/datatypes-definitions#Expression.description)** [0..1]: [string](/string) A brief, natural language description of the condition that effectively communicates the intended semantics
- **[Expression.name](/datatypes-definitions#Expression.name)** [0..1]: [code](/code) A short name assigned to the expression to allow for multiple reuse of the expression in the context where it is defined
- **[Expression.language](/datatypes-definitions#Expression.language)** [0..1]: [code](/code) The media type of the language for the expression
- **[Expression.expression](/datatypes-definitions#Expression.expression)** [0..1]: [string](/string) An expression in the specified language that returns a value
- **[Expression.reference](/datatypes-definitions#Expression.reference)** [0..1]: [uri](/uri) A URI that defines where the expression is found

## Bindings

- **Expression.name**: `!`
- **Expression.language**: `ExpressionLanguage` | strength: value set | reference: valueset-expression-language

## Requirements

- **Expression.language**: The cardinality of this element is optional to allow text only as part of the authoring process. However, in order to be executable, the expression element must be specified.

## Comments

- **Expression.expression**: If Expression.expression and Expression.reference are both present, the Expression.expression might just be a name pointing something within the referenced content.
- **Expression.reference**: If both a reference and an expression is found, the reference SHALL point to the same expression