Exploring Graphical Feedback in a Demonstrational Visual Shell

. We present a visual language that serves as a novel form of feedback in a Programming by Demonstration (PBD) interface. The language explicitly represents data, such as files, with unique icons and implicitly represents operations by changes to data icons, so that operations reflect the changes seen in the interface when executed. In addition, the language is used to provide feedback to the user by indicating loops and inferred sets, specifying parameters, etc., and is integrated into other parts of the PBD system, such as the editor. This forms a close union between the interface, the PBD system and the program representation and helps bridge the gap between the user's mental model of the programming process and the actual programming task. 1 Introduction In his classic 1983 article, Ben Shneiderman introduced the concept of a "direct manipulation" interface, in which objects on the screen can be pointed to and manipulated using the mouse and keyboard[25]. The Apple Macintosh, intr..