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AgentSheets®: an Interactive Simulation Environment
with End-User Programmable Agents
Alexander Repenning AgentSheets Inc., Gunpark Drive 6560, Boulder, Colorado, 80301, email: Center for LifeLong Learning and Design, Department of Computer Science, University of Colorado at Boulder, Campus Box 430, Boulder, Colorado 80309-0430, email: Current Information Technology is mostly focused on With the dawn of the new millennium we are reflecting on accessing information and provides little support for the relatively short history of the information age. Yes, we processing information. An exponentially growing amount have come a long way from the early beginnings. The of information becomes increasingly unmanageable with Internet has matured from being a peculiar playground of a today's information technology approaches. Through web handful of researchers to a rapidly growing network portals, emails, chat rooms, and news lists all kinds of connecting people, resources and services all over the information can be accessed everywhere, all the time.
planet. The rate of adoption is truly astonishing. In just 7 Often embedded in rapidly flashing animations the years the Internet has attained a market share of 25%. It information glut is fighting for our attention and we are took telephone 35 years to achieve the same penetration.
fighting to locate relevant information. The ability to access information is a crucial first step but now we need In a technological context, reflection is often accompanied to explore new means of processing information. How can by prediction. What is next with information technology? we keep up with frequently updated website content and What will we be able to do with technology, what will setup autonomous computation helping us to process that technology do to us? On an analytical level we have tools such as Moore's law helping us to capture technological growth as mathematical functions. According to Moore's End-user programmable agents are a means to give people law the speed of computer chips doubles every 18 months.
autonomous information-processing power. Simulation is a Despite earlier calls for caution this has been true for many form of information processing. Agents can be used to years. Even growth limitations attributed to physical build interactive simulations. AgentSheets® is an agent- constraints such as molecular limitations regularly have based simulation-authoring tool that allows end-users to been overcome with new innovations. Maybe as soon as build interactive simulations and publish them as Java this or the next year we will see the first consumer PCs applets on the web. Interactive simulations can help people featuring 1 Giga Hertz clocked CPUs. Soon thereafter we to explore complex issues and communicate them to other will forget that there ever were CPUs operating at non- people effectively. Interactive simulations are more Giga Hertz speeds. Mega Hertz measurements will no engaging than static text, images and even video.
longer be associated with computers at all. Instead all we Moreover, people can define the behavior of end-user will associate with Mega Hertz measure will the frequency programmable agents to access existing information such of FM radio stations.
as stock ticker symbols and to process that information by analyzing and synthesizing it.
Another kind of growth equally astonishing as the growth of computing speed is the growth of information spaces.
Just like the speed of CPUs the number of websites on the Internet is growing exponentially. Since we are running distributing interactive content. Interactive content such as out of valid internet IP numbers, soon we need to replace simulations cannot be captured on a static, paper-based, the current internet addressing scheme with a new one medium. By now, the computational power of personal capable to deal with this kind of growth. Plotting the computers has reached the necessary levels to run amount of information accessible via the Internet and the sophisticated simulations that would have required a computing speed versus time we cannot react any other supercomputer only a couple of years ago. Using way than being genuinely impressed with information technologies such as Java and Flash, interactive content technology. No other technology ever has changed our can be embedded in web pages and made accessible to lives so rapidly, so profoundly.
everybody on the planet with a web browser.
How do we benefit from increasing information volume By now the idea of featuring interactive content on the and computing speed? A loaded question to be sure. It is Internet is not all that new anymore. However, the not clear what the exact shape of the curve would be if we applications of interactive content discussed here are were to plot the average Intelligence Quotient (IQ) or – if different in the sense that people who are not programmers there would be such as thing – the Creativity Quotient over or web designers have built this interactive content. The time. My fear is that IQ and CQ would look remarkably quest is the exploration of new tools that will enable flat next to CPU speed and information volume. Maybe computer end-users to build interactive content very much this is not terribly surprising but it still raises a number of in the same spirit as tools – now called word processors – essential issues. Just how it is possible that with more have enabled end-users to build static content on their information accessible and with more computation power computers. The specific tool discussed here called available we still fail to experience any kind of profound AgentSheets is only one instance of a more general impact on the qualitative aspects of live such as education? framework of end-user tools to author interactive content.
The average degree of understanding of the world (science, No detailed description of AgentSheets can be given here.
politics, nature, etc.) appears not to have changed much Following a quick overview of the AgentSheets authoring despite the fact that most answers to complex questions tool is a description of how people have used AgentSheets may be just one web search away.
to build simulations which, in turn, have been used to communicate complex ideas or to further their own ECommerce has become the most celebrated application of understanding in ways impossible with static media.
the Internet. Jeff Bezos, CEO of was just selected to be "1999 Person of the Year" by Time AgentSheets: A Simulation Authoring Tool
magazine for his pioneering success with eCommerce. I do not wish to attack these efforts in any way – I order most Combining Java authoring, end-user programmable agents of my books from Amazon – but really hope that as a and spreadsheet technology, AgentSheets [Repenning and society we can push the internet beyond the aspiration of Sumner 1995] [Repenning, et al. 1998] turning the web into a gigantic virtual shopping mall.
( is an authoring tool that Despite the rapid, again exponential, growth of shopping empowers casual computer users with no formal transaction on the web it is unlikely that in the end more programming training to build and publish web-based people are reading books. There simply have to be information technology applications that have the potential to truly enrich life and not just to serve as a commodity.
Today's Internet killer apps (email, and eCommerce) push old types of content such as text, images and videos, through new media. What kind of other content types could there be and how can people use them to do what? In the remainder of this paper some scenarios are presented in which information technology is used as medium have used AgentSheets and VAT to create interactive simulations and games in a variety of disciplines including computer science, environmental design, fine art, robotics, music, history, and biology. In an elementary school science class, students created ecosystem simulations to explore food webs and sustainability issues. In a high school history class, students created social and historical simulations. Scientists working with NASA created simulations of E.coli bacteria fermenting in zero gravity.
Figure 1. AgentSheets combines Agent, Spreadsheet and
Java Authoring technology
AgentSheets enables users to create such simulations, using its end-user programming language Visual AgenTalk® (VAT). Users design agents' looks by drawing icons and create agents' behaviors by composing VAT conditions and actions from command palettes into rules. Conditions and actions allow agents to do a variety of operations including: compute spreadsheet-like formulas react to mouse clicks and key strokes Figure 2: SimProzac: Simulation running in a webpage
sense other agents explaining how Serotonin works in the Synapse and how
send messages to agents Antidepressants affect the system.
play sampled sounds and MIDI instruments Figure 2 above shows an interactive simulation explaining the effects of Prozac to patients by modeling a serotonin gather information from web pages synapse in the brain. The simulation was built by a psychiatrist for his patients. For this particular simulation, Visual AgenTalk employs a new approach to end-user a suite of agents (Table 1) was created by specifying their programming called Tactile Programming. Tactile look and their behavior using the Visual AgenTalk Programming primitives and programs not only have language. Figure 3 illustrates two VAT rules from the enhanced visual representations to help program behavior of the Serotonin molecule defining animation and readability, but also have interactive interfaces to assist interaction with membranes.
with program writability. Tactile Programming is well suited for collaborative use since it eases program composition, comprehension and sharing [Repenning and Ambach 1996] of behaviors.
A wide spectrum of users, ranging from elementary school students with no programming background to scientists, at the center of the sense-making process and suggest that students learn by actively building their own understanding of a topic. One promising approach to meaningful learning and robust understanding of science centers on the creation and use of computer simulations as representations of how and why things work [Papert and Harel 1993]. Activities with simulations have the potential to help children organize, develop, test, and refine their ideas about Figure 3: Part of the serotonin behavior which specifies that if
the serotonin looks like
, it will change to
, or with 15%
chance if the serotonin sees a membrane to its right, it will
move to the right.
The specific point of building the SimProzac simulation was to communicate complex chemical interactions to patients. The web serves as an ideal platform to harness the communicative power of interactive simulations such as SimProzac. Entire AgentSheets simulations can be exported as Java applets and JavaBeans, using the Ristretto™ Agent-to-Java-Byte-Code generator [Repenning and Ioannidou 1997]. This allows simulations Figure 4. A simulation world populated with animal agents
to be published on the web making them accessible to a designed by kids
larger community of users. Using Ristretto™ the serotonin simulation was turned into a Java applet (Figure 2).
The Science Theater/Teatro de Ciencias (sTc) project has developed a number of activities with simulations for elementary school students [Rader, et al. 1998]. The Using Simulations in Lifelong Learning
EcoWorlds curriculum for 4th and 5th graders focuses on a AgentSheets appeals to an unusually wide range of users.
number of content areas, including characteristics of This general applicability makes AgentSheets an ideal tool organisms, structure and function in living systems, for lifelong learning including K-12 education, University populations and ecosystems, and diversity and adaptations level education and workplace training [Gina Cherry, et al.
of organisms. The EcoWorlds unit addresses these issues 1999]. Justin Martin [Martin 1998] put the market by having students work in small groups to create potential of lifelong learning into numbers: "The computer simulations of ecosystems in different Knowledge-based economy is in full bloom. America's environments such as the arctic or a desert. Activities with investment in lifelong learning—everything from teaching simulations are integrated into a curriculum, which kids in the schools to training adults in the work incorporates hands-on activities, research activities, and force—runs to $665 billion a year, more than is spent on class discussions.
national defense." In the Science Theater activity kids collaboratively design The following sections provide a sense of the applicability animals and exchange them through the Behavior of AgentSheets by presenting example projects.
Exchange. The Behavior Exchange is a web-based repository of agents allowing AgentSheets users to share useful agents with each other Elementary Schools: EcoWorlds
Current reform efforts in science education emphasize constructivist pedagogies - approaches that place students present their own thoughts and ideas for their final One of the groups that chose to do a final project using AgentSheets selected the topic of the California Grape Boycott in the context of the Chicano/a, Latino/a Civil Rights movement. The project, as the students defined it, consisted of building a Web page with a boycott simulation which they had created, as well as links to related Web sites. In fact, these students' Web site served as a small virtual library on the subject.
Figure 5. The Behavior Exchange is a web-based repository of
agents. Users can share their agents with other users.
The process of designing animals and exchanging them to build a joint simulation is new, engaging way to learn about complex system collaboratively. The motivation of building simulations was so high that student were found to return early from their lunch breaks in order to tweak their simulations. The same students had never returned early from their lunch breaks to read books.
Figure 6. A student produced webpage containing a
In this example information agents capture information simulation of the Californian Grape Boycot
processing. These agents are built and distributed as a form In order to build the simulation, the students realized that of collaboration between computer end-users.
they needed to find out about the history of the boycott and High Schools: The Grape Boycott
of the United Farm Workers movement. The students did some initial research in the library and on the Web to learn At the high school level, simulations were used in John the basic historical facts, and found relevant information in Zola's "Protest and Reform" history class at New Vista Web pages, which they could reference on their own Web High School [Ioannidou, et al. 1998]. In this class, students had the opportunity to study protest movements throughout U.S. history (e.g. the Civil Rights movement and the anti- Vietnam war movement), and to learn about theories of In modeling applications simulations are used to explore protest and social change. Initially, simulations were used complex causalities between a set of interacting variables.
in this context to present some of the concepts of protest The reasons why people build models include issues such and reform through "Segregation" and "Protest March" the price of running a physical experiment (for instance it simulations created by the researchers using the is very expensive to explore the effects of micro gravity by AgentSheets system. Students also created simulations to putting an experiment aboard a Space Shuttle), and the danger of operating an experiment (for instance an experiment melting the core of a nuclear power plant).
The use of simulation technology is not limited to Modeling is most beneficial to simulation builders. The traditional screen-with-mouse interaction approaches. New model becomes an instrument of the explorative thinking display and interaction techniques when combined with process allowing the builder to test new hypothesis leading simulations result in a new kind of tangible interactive to new insight and understanding. An example of an medium. Professor Ernesto Arias from the University of interactive simulation model created by scientists at the Colorado school of Architecture & Design is concerned BioServe Space Technologies center is shown below with decision making as a public process. He has been (Figure 7). The simulation models the behavior of E.Coli using AgentSheets in many of his courses, and is now bacteria in microgravity and explores its implications for working with the Center of LifeLong Learning & Design fermentation biotechnology [Klaus 1998].The goal of the on new interface technologies that bring the power of model is to explain why E.Coli bacteria behave simulations to the public. He envisions information kiosks fundamentally different in microgravity situations such as located in public buildings such as libraries. Using a aboard the Space Shuttle orbiting around the earth. The display technology called SmartBoard, he is building process of building this model has helped the BioServe simulations that combine the physical world with the scientists to better understand complex molecular virtual world. Physical objects such as LEGO blocks can interactions involving bacteria cell sedimentation cell be placed onto a vertical version of the SmartBoard (see diffusion, byproduct diffusion and nutrient uptake.
Figure 8). The virtual world is an AgentSheets simulationof the Boulder bus system. Along with members of the healthy community initiative, Professor Arias is exploring issues such as public transportation and pollution.
Community members experience public transportation scenarios either personally, by interacting with the physical virtual simulation, or over the web.
Figure 7. E.Coli bacteria are situated in a low-gravity
environment and are slowly sinking toward the bottom of the
cell. Glucose is absorbed and converted into waste products.
From a learning perspective modeling is useful because it helps simulation builders to explore new ground. The Figure 8. A Physical + Virtual Simulation running AgentSheets
on SmartBoard (horizontal in front and vertical in back)
physical experiments that have been in the MIR space station and were part of the 5 Space Shuttle missions are Connecting Simulation to other Components
costly and need extensive preparation. The simulation, in contrast, can be varied at any time and run in parameter Interactive simulations could be turned into a richer ranges that cannot be replicated with the physical learning activity if they could be connected to other educational components such as plotters, databases, and spreadsheets. Addressing these kinds of issues the National Science Foundation is supporting the Educational Software Ioannidou, A., Repenning, A. and Zola, J. 1998.
Components of Tomorrow [ESCOT] project with the goal Posterboards or Java Applets? InInternational Conference of exploring the use of Java-based component technology of the Learning Sciences 1998 (Atlanta, GA). Association in education [Roschelle, et al. 1999]. To this end ESCOT of the Advancement of Computing in Education, 152-159.
brings together researchers, practitioners, developers, curriculum designers, publishers and content experts.
Klaus, D. M. 1998. Microgravity and its implications for Along with SimCalc and Geometer's Sketchpad®, fermentation biotechnology. Trends in Biotechnology 16, AgentSheets is one of the cornerstone ESCOT tools to generate educational components and build math activities.
Martin, J. 1998. Lifelong Learning Spells Earnings.
In Figure 8 an AgentSheets simulation called the Virus Fortune 138, 1, 197-200.
Attack simulation is connected to the SimCalc graphing component to plot the number to infected people while the Papert, S. and Harel, I. (Ed.). 1993. Constructionism.
simulation is running. This allows users to track the Norwood, NJ: Ablex Publishing Corporation.
spreading of the virus through graphical and numeric data, Rader, C., Cherry, G., Brand, C., Repenning, A. and as well as simulated visual data.
Lewis, C. 1998. Designing Mixed Textual and Iconic Programming Languages for Novice Users. InProceedings of the 1998 IEEE Symposium of Visual Languages (Nova Scotia, Canada). Computer Society, 187-194.
Repenning, A. and Ambach, J. 1996. Tactile Programming: A Unified Manipulation Paradigm Supporting Program Comprehension, Composition and Sharing. InProceedings of the 1996 IEEE Symposium of Visual Languages (Boulder, CO). Computer Society, 102- Repenning, A. and Ioannidou, A. 1997. Behavior Processors: Layers between End-Users and Java Virtual Figure 9. ESCOT Connected Math activity combining
Machines. InProceedings of the 1997 IEEE Symposium of AgentSheets Virus Attack simulation component (left) with
Visual Languages (Capri, Italy). Computer Society, 402- SimCalc plotting component (right).
Repenning, A., Ioannidou, A. and Ambach, J. 1998. Learn to Communicate, and Communicate to Learn. submitted to AgentSheets research and AgentSheets Inc. are supported Journal of Interactive Media in Education .
by the National Science Foundation (DMI 9761360, REC 9804930, REC-9631396, RED 9253425, CDA-940860).
Repenning, A. and Sumner, T. 1995. Agentsheets: A Medium for Creating Domain-Oriented Visual Languages.
IEEE Computer 28, 3, 17-25.
Gina Cherry, Andri Ioannidou, Cyndi Rader, Cathy Brand Roschelle, J., DiGiano, C., Koutlis, M., Repenning, A., and Repenning, A. 1999. Simulations for Lifelong Phillips, J., Jackiw, N. and Suthers, D. 1999. Developing Learning. In National Educational Computing Conference, Educational Software Components. IEEE Computer 32, 9, NECC '99 (Atlantic City, NJ).
Table 1: Application Domains for Interactive Simulations
K-12 Education: High School
How does a TV work? This simulation illustrates how a picture
is scanned in by a camera (left), transmitted to a TV set and converted back in to a picture (right). Users can paint their own Interactive Story Telling: History students create interactive
pictures and play with TV signal processing parameters.
stories of historical events such as the Montgomery bus boycott.
Learning by visualization and modeling: The effects of
Learning by taking apart: What makes a bridge stable? The
microgravity onto E.coli bacteria are modelled by NASA. This is goal presented to the users of this simulation is to remove as a simulation of an experiment that was aboard the Space Shuttle many elements of the bridge as possible without making the with John Glenn. This simulaton requires several thousand bridge collapse. A number of connected issues are revealed including forces, architecture, and geometric perspective. This simulation was featured on the PBS Mathline.
Learning through simulation use: This simple voting
Learning through design : Even if the finished simulation/game
simulation explains concepts such as clustering, migration and is not directly related to educational goals, the process of stability of two party systems. Can it predict the outcome of the building the simulation may be very educational. The Ultimate election in 2000? Pacman is a complete game based on complex Artificial Intelligence algorithms and the non-trivial math of diffusion


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