41.5 How SiriKit Integration Works
Siri integration is performed via the iOS extension mechanism. Extensions are added as targets to the app project within Xcode in the same way as other extension types. SiriKit provides two types of extension, the key one being the Intents Extension. This extension contains an intent handler which is subclassed from the INExtension class of the Intents framework and contains the methods called by Siri during the process of communicating with the user. It is the responsibility of the intent handler to verify that Siri has collected all of the required information from the user, and then to execute the task defined in the intent.
The second extension type is the UI Extension. This extension is optional and comprises a storyboard file and a subclass of the IntentViewController class. When provided, Siri will use this UI when presenting information to the user. This can be useful for including additional information within the Siri user interface...