The World Wide Web Consortium (W3C) draft for a "System Information API" specifies JavaScript functions for accessing the battery, CPU, sensors and other hardware characteristics of a device. For this purpose, the window.navigator object's SystemInfo interface has to implement the get, set and watch methods. set can only be applied to some screen properties such as brightness and orientation, while all other hardware properties are marked as readonly. watch is used for monitoring readings, for example those of a heat sensor.