1. An integrated development environment for developing user interface documents, comprising: an editor to edit a user interface document; an adaptation engine to generate device class specific representations of the user interface document, each device class specific representation referring to a respective device class; the integrated development environment further comprising a device class dependent complexity indicator to determine complexity values of layout components of the device class specific representations by using complexity evaluation functions, associated with the layout components and to aggregate the complexity values by device class according to a corresponding layout component hierarchy of the respective device class specific representation.