# Preliminary_Trigger A condition that, when met, performs an action. ## Discussion Because it inherits `Typed`, this schema declares a `Preliminary_Trigger` as a type of prim. For more information about typed schemas, see USD Specification > [Typed](http://graphics.pixar.com/usd/docs/USD-Glossary.html#USDGlossary-TypedSchema). The runtime executes triggers based on: - User input, like a user’s tap gesture. - Scene state, including a prim’s proximity to the user’s device. - Programmatic conditions, like application state or a function result. ### Declaration ```other class "Preliminary_Trigger" ( inherits = ) ``` ### Add a tap trigger to a cube The following example shows how a prim named `TapCube` opts in to notification of user taps. ```other #usda 1.0 def Cube "Cube" {} def Preliminary_Trigger "TapCube" { uniform token info:id = "TapGesture" rel affectedObjects = [ ] } ``` ## Topics ### Properties [info:id](/documentation/USD/info-id) The action’s unique identifier. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)