CPN2000: Advanced Interaction Techniques for Complex Systems

The CPN2000 project is an ongoing research project exploring advanced graphical interaction techniques and user interface modeling for the editing and simulation of Coloured Petri Nets.

The project started a year ago and has already produced a functional system that demonstrates a number of novel interaction techniques and their integration within a consistent user interface. Unlike standard graphical applications, the system does not use menu bars, scrollbars or dialog boxes, and there is no need to select objects before editing them. Yet the system is much faster to operate than a traditional desktop interface. Windows are replaced by "pages" that can be bound together into "binders", making it easy to flip between pages and organize the workspace. A trackball, operated by the left-hand (if you are right-handed) complements the mouse. Using these two input devices, it is possible to resize and zoom objects by stretching them as one would do with a physical object. It is also possible to move an object with the right hand while flipping pages with the left hand to find its destination. Another two-handed input technique consists in moving a transparent palette called a toolglass with the left hand while clicking through the palette tools with the right hand. Studies have shown that this type of interaction is up to 40% faster than traditional tool palettes. Finally, circular menus that pop-up where the mouse is clicked allow a very quick selection of commands, up to three times faster than traditional menus. The menu does not even appear when the selection is made quickly. This allows for very fast selection without the need to learn keyboard shortcuts.

This new interface combines these interaction techniques in a way that streamlines the work of a Coloured Petri Net designer. For example, rather than aligning objects, one creates a guideline and "sticks" the objects to be aligned to it. Moving the guideline then moves all the objects at once. Changing the visual styles of object is achieved by copying the style of another object rather than using a complex dialog box. The design of the new system was driven by our studies of users of Coloured Petri Nets and by their input during the design process. Using the same set of interaction techniques and the same design process, other application areas could benefit similar gains in productivity.

The project is carried out by the Devise group, a cooperation between three different research groups at the University of Aarhus. The Human-Machine Interaction group contributes with the expertise within interaction methods and user interfaces. The research group within the object oriented language, BETA, contributes with the programming language and the programming environments which are used for the implementation. Finally, the Coloured Petri Net group contributes with the theory behind the simulation software which is developed. The project is funded by CIT, Hewlett-Packard and Microsoft and has 10 researchers.

The first official release of the new system is planned in September 2000. It will run primarily on PCs equiped with an OpenGL-capable video card, but also on MacOS and on various flavors of Unix including Linux.

Using a trackball in the left hand in addition to the mouse in the right hand makes it possible to design more efficient interaction techniques. Of course, left-handed users can reverse the setting.

(Click image to enlarge) This image shows three binders. The bottom one contains 6 pages, the second of which is currently visible. The left part of the screen is the index, which gives access to all the tools and pages in the system. Next to it is a circular contextual menu to manipulate pages. The two pages at the top show the same part of the diagram at different scales. The page at the bottom has a transparent toolglass, controled with the left hand, to change the colors and thickness of objects. To the left is a more traditional tool palette with VCR-like buttons to control the simulation of the Coloured Petri Net.