Building User Interfaces: Organizing Software Agents

ing combines and transforms events coming from the presentation techniques into higher level events for higher abstractions. Conversely, concretizing decomposes and transforms high level information into low level information. The lowest level of the dialogue controller is in contact with the presentation techniques provided by the toolkit. This boundary is a rather fuzzy frontier. In general, user interface toolkits such as the X Intrinsics, provide an abstraction mechanism for defining new interaction techniques. However, it is not always possible to build new interaction techniques from the predefined building blocks of the toolkit. For example, in an earlier version of the X intrinsics, interaction techniques would occupy rectangular areas only. In such conditions, the notion of a wall in a floor plan drawing editor, could not be implemented as a diagonal line widget. Instead, a presentation object "wall" would be defined as a new abstraction in the dialogue controller portion. Thi..