Multimodal communication has already been described in Section 2.1 . Multimodal communication is especially important in situations where the user cannot afford to spend all the senses on a certain task. If the user e.g., needs to take a closer look at something as a particular part in mechanics, it would not be a good idea to make the computer produce visual output. Then it would be very disturbing for a user to be forced to grab, position, and activate an additional 2D mouse just to select a simple command from the 2D interface. Here, speech input would be a reasonable solution.
Natural language is one of the best methods to make a system more intuitive.
Intelligent help systems provide help to the user that the latter would most likely need in a particular situation. This way, the UI becomes less confusing, functionality becomes directly accessible, and the entire work process is speeded up. The question whether the system decides on such adaptations of the interface autonomously or controlled by the user is a basic issue of adaptive user interfaces and, therefore, discussed in the corresponding Section 4.3 .