Set this property to a value that identifies the user activity so you can later delete it with deleteSavedUserActivitiesWithPersistentIdentifiers:completionHandler:. For example, if the user checks the weather for Cupertino each morning from home, the weather app sets the persistent identifier to the city name (Cupertino). When the user deletes Cupertino from the weather app, the app deletes the user activity associated with the identifier, "Cupertino".
A set of localized keywords that can help users find the activity in search results.
This documentation contains preliminary information about an API or technology in development. This information is subject to change, and software implemented according to this documentation should be tested with final operating system software.