Alexander Repenning

Dr. Alexander Repenning              _/        _/_/_/     _/_/_/
President and CEO                 _/  _/    _/             _/
AgentSheets Inc.               _/_/_/_/_/    _/_/_/       _/
6525 Gunpark Dr., Suite 150   _/      _/          _/     _/
Boulder, CO 80301            _/      _/    _/_/_/     _/_/_/
________________________________________________________________            phone: (303) 530-3533                  fax: (303) 530-1067

(Excerpt from CHI 97  SIG report:)
He has tried to make "behavior processors" with which users can construct worlds of programmed agents, just as they use word processors to construct documents.  See the CHI97 talk and participatory demo on "Social Behaviour Processing", by Alexander Repining and James Ambach; browse -- follow the link to "Child's Play."  Alex's solution to the expressiveness-usability tradeoff is graphical rewrite rules.  These are "if...then" rules with graphical icons as conditions and actions.  For example:  IF (picture of car on highway with empty road in front of it) THEN (same picture with car moved forward) causes the car to move down the highway on each simulation cycle until it encounters an obstacle.  Analog constructs, such as variables that can be calculated and colors that blend smoothly based on their value, permit more sophisticated simulations.  For example, in a bridge-building game the blocks in the bridge turn different shades of red depending on the stress applied to them, or the colors in a weather map vary by a model of temperature between recording sites.  Using this metaphor, he has found that children can create fairly complex programs, robots, etc.

The major tools that incorporate these principles are:  Agentsheets&Visual AgenTalk (AgenTalk is the graphical rewrite rule environment.)  Both are written in Lisp and run only on Macintosh, but a company formed to commercialize them is porting to other platforms including PC Windows.  Another thrust of Alex's group is to  incorporate the World-Wide Web:  "Simulation meets Browser."  For example the temperatures in the above weather map are gleaned from a large number of weather sites by a tool that lets users specify where on each Web page to find the temperature(s) of interest.  Simulations can be shared across the Web:  an agent with its behavior and appearance can be dragged out of a browser and dropped into a an AgentSheets simulation.  His most recent innovation (with James Ambach) is Ristretto ("Java without the aftertaste"), a translator which creates an execute-only Java representation of an AgentSheets simulation that can execute on any computer over the Web.

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