This not only includes the input devices through which the user communicates with the system, but also the application objects that the system provides to the user. This is done in accordance to predefined lexical and syntactic rules of conversation that users need to follow in order to be able to use the system.
Examples are command languages, query languages, and question answer dialogues.
In model world interaction styles, the user interacts with the application system within a spatially and visually presented world consisting of a user-interface and application objects. The users no longer need to know anything about the system-specific mechanisms that map their actions to the systems' functionalities. Multimodal interaction combines natural language with other input modes such as gestures, thus supporting a much more intuitive approach to human-computer interaction.