Backward and forward chaining - our nascent

As computer graphics evolves and expands into an essential component of many interactive systems, it is almost inevitable that the applications themselves become more complex and ambitious. In particular, the interactive system is rapidly becoming the intelligent system: Not only does the interface permit convenient access to the entities and operations of the application, but it also aids and augments the mere interaction in significant ways. For example, computer-aided design systems check topological constraints while an object is being constructed, robot simulators assist in avoiding collisions, and slide-making systems have automatic layout modes. The implication of these aids is that the new generation of graphical systems will provide increasing intelligence in the human-computer interface. The study of the characteristics and capabilities necessary to effect communication between human and machine on this higher level is a central aspect of Artificial Intelligence (AI). One of our principal goals in presenting this special issue is to bring the approaching confluence of computer graphics and artificial intelligence into sharper focus. In addition, we hope to spur interest in common issues and open new pathways for future graphical systems. The fields of artificial intelligence and computer graphics have interacted in a number of ways in the past. This interaction has been particularly strong in the areas of image processing and robotics. Image processing and graphics are naturally related because they share a common