paper: other ways to program

Drawing on Napkins, Video-Game Animation, and Other Ways to Program Computers
Ken Kahn
Communications of the ACM, Vol. 39, No. 6, 1996

This article describes a number of visual, interactive methods to programming. The main thesis is that visual programming environments have failed to date because they are not radical enough. Programs exhibit dynamic behavior that static visuals do not always convey appropriately and so dynamic visuals, or animation, should be applied. Furthermore, visual programming can avoid explicit abstraction (i.e. when visuals become just another stand in for symbols in a formal system) without necessarily sacrificing power and expressiveness. Put more abstractly, a programming language can be designed to use one of many possible syntactical structures. It then becomes the goal of the visual programming developer to find the appropriate syntax that can be mapped to the desired language semantics. To map an existing computer language (e.g., C or LISP) into a visual form would require the use of a visual syntax isomorphic to the underlying language. Doing so in a useful, intuitive, and learnable manner proves quite difficult.

Kahn describes a number of previous end-user programming systems. This includes AlgoBlocks, which allow users to chain together physical blocks representing some stage of computation. The blocks support parameterizations on them, and afford collaborative programming. Another system is Pictorial Janus, which uses visual topological properties such as containment, touching, and connection to (quite abstractly, in my view) depict program performance.

He goes on to describe a (quite imaginative) virtual programming "world", ToonTalk, which can be used to construct rich, multi-threaded applications using a video-game interaction style. The ToonTalk world maps houses to threads or processes, and the robots that can inhabit houses are the equivalent of methods. Method bodies are determined by actually showing the robot what to do. Data such as numbers and text are represented as number pads, text pads, or pictures that can be moved about, put into boxes (arrays or tuples), or operated upon with "tools" such as mathematical functions. Communication is represented using the metaphor of birds -- hand a bird a box, and they will take it to their nest at the other house, making it available for the robots of that abode to work with the data.

Kahn argues that while such an environment may be slower to use for the adept programmer, it is faster to learn, and usable even by young children. It also may be more amenable to disabled individuals. Furthermore, its interactive animated nature (you can see your program "playing out" in the ToonTalk world) aids error discovery and debugging. In conclusion, Kahn suggests that these techniques and others (e.g. speech interfaces) could be integrated into the current programming paradigm to create a richer, multimodal experience that plays off different media for constructing the appropriate aspects of software.

Inspiring, yes, but quite difficult to achieve. My biggest question of the moment is: what happened to Ken Kahn? The article footer says he used to work at PARC until 92, and then focused on developing ToonTalk full-time. I'll have to look him up on the Internet to discover how much more progress he made. While I'm skeptical of these techniques being perfected and adopted in production-level software engineering in the near future, I won't be surprised if they experience a renaissance in ubiquitous computing environments, in which everyday users attempt to configure and instruct their "smart" environs. If nothing else, VCRs could learn a thing or two...