# Untitled undefined type in property reference Schema

```txt
https://amazonalexa.com/ask/2020/12/PropertyReference#/properties/expression
```



| Abstract            | Extensible | Status         | Identifiable            | Custom Properties | Additional Properties | Access Restrictions | Defined In                                                                              |
| :------------------ | :--------- | :------------- | :---------------------- | :---------------- | :-------------------- | :------------------ | :-------------------------------------------------------------------------------------- |
| Can be instantiated | No         | Unknown status | Unknown identifiability | Forbidden         | Allowed               | none                | [PropertyReference.json\*](../../schemas/PropertyReference.json "open original schema") |

## expression Type

merged type ([Details](propertyreference-properties-expression.md))

one (and only one) of

*   [Call](actiondeclaration-properties-annotations-call.md "check type definition")

*   [property reference](arguments-definitions-arg-expression-oneof-property-reference.md "check type definition")

*   [name](arguments-definitions-arg-expression-oneof-name.md "check type definition")