A model for authoring virtual experiments in web-based courses

Albert Ip

Multimedia Education Unit

The University of Melbourne

Parkville, VIC 3052

email: a.ip@meu.unimelb.edu.au

Ric Canale

Multimedia Education Unit

The University of Melbourne

Parkville, VIC 3052

email: r.canale@meu.unimelb.edu.au


This paper introduces a conceptual model of "virtual apparatus" for designing virtual experiments with the emphasis on minimising the technical burden on the teacher by using generic programmable objects. A virtual apparatus is a reusable software component which non-programmers can set-up and modify using a forms based interface. Some virtual apparatus behave like real world objects such as a beaker or pulley and provide a simple and intuitive interface for the teacher. Like its real world counterpart, a virtual apparatus can be used by a teacher and students in an experiment. Other virtual apparatus may be hidden, performing monitoring functions to provide feedback to the teacher as well as providing a mechanism for moving the simulation from novice to more advanced levels. For this concept to be viable over Internet, these apparatus must adhere to a strict set of open and common software specifications to ensure inter-operability between virtual apparatus from different sources and perform across different computing platforms.

1. Introduction

Virtual experiments, or simulations, are highly valued teaching and learning tools. Virtual experiments are not exact duplicates of their real-world counterparts, and therefore can provide educationally valuable features not available in real world experiments. Some early adopters recognise this. In his introduction of his virtual Physics laboratory at the University of Oregon, (Bothun 1996) states:

"In the interest of providing students with truly interactive texts, ... These experiments are meant to be conceptual interfaces to the equations of physics and/or represent interaction with data that simulates a real physical experiment. The whole purpose is to shape student-driven inquiry and to lead students through the discovery process which is what science really is."

He goes on to say that:

"Some experiments duplicate what could be done in the lab (eg. the virtual circuit) while others can't really be done in the lab even though they are relatively straight forward (eg. Newton's Second Law applet). "

An experimental study of Newton's second law requires a frictionless experimental environment and a point mass, ie an object with mass but without volume. The best analog in real world can never compare to the simplicity and elegance of a virtual experiment of this kind.

Another interesting example of a virtual experiment is a simulation of a nuclear power plant (Eriksson, 1996) where the user tries "to keep the reaction stable when component failures occur!".

Running the risk of a learner-operator causing a serious mishap in a real nuclear power plant just for the sake of learning how to control the power plant properly is clearly an unacceptable level of risk.

There may also be a resource-related rationale for using virtual experiments. For example, some virtual experiment sites may have saved the lives of many frogs (Eriksson, 1994; Kinzie, 1994). The images of the frog in the first web site are computer-generated and the second web site takes another approach, in which photos and movies are used to follow an actual frog dissection.

So too, the visible human project (US National Library of Medicine, 1995) may provide source material for virtual experiments such as fly throughs of organs simulating medical procedures such as colonoscopy (Kaufman, 1995)

As the level of interactivity offered by a web-based education system develops higher levels of sophistication, the learners' expectations will simply grow at a faster pace. It is becoming more and more difficult for educators to cope with the ever-increasing demand to author interactive on-line course materials. This paper looks at a model which may minimise the technical demands placed on teachers wishing to explore the benefits of virtual experiments.

2. Technology overview

To create a reasonably responsive virtual experiment, a compromise has to be made to balance the requirements of communication and computation. In general, when the computation power is provided by a server, the demand on communications will be high. One example of using the server to provide the computation is the virtual frog experiments above where a powerful server is used to process the requests from the clients and return the images in a generated html page. This approach is suitable in situations where the main processing cannot be provided by the client's machine (eg a large amount of image rendering, creation of on-demand movies etc.) This approach also generates a lot of traffic on the network and the response time is usually unpredictable.

When sufficient computational power is provided by a local client machine, there will be less demand on communications. One example is the virtual Physics experiments at the University of Oregon. The examples cited above are implemented using Java and/or JavaApplet. The simulation is an application by itself and is running at the client-side. All we need to view and work with the simulation is a Java-enabled browser such as Netscape 2.0 or above. The initial download may take a while, thereafter, the processing is all done by the client machine and hence is independent of the network traffic conditions. At present, a fairly high-end desktop machine would be necessary to provide sufficient computing power.

This paper focuses on a model of implementation assuming that the computation power is provided by a client machine, but connected to the Internet for initial data requests and download.

The complex technical requirements needed to create interactive virtual experiments are some of the major hurdles that educators need to overcome before we can see mainstream adoption of this concept. We believe that all the examples quoted above are supported by competent support personnel and/or are major funded research projects. To take this technology into mainstream education, we need to make the creation of the content much easier.

3. Educational Overview

In real world experiments, apparatus are typically acquired from some apparatus manufacturers. A teacher would design an experiment basing on the apparatus available. The instruction to the learner will typically describe how the experiment would be set up using the available apparatus, how these apparatus would be manipulated to alter some of the experimental conditions, how to watch and take note of the changes and how to interpret the results. Such didactic instructions would not be very motivating and provide little room for the learner's own exploration.

A more learner-centred approach would be to give a set of guidelines (not exact experimental procedures) and ask the learners to design and work through the experiments themselves. However, there are logistic limitations of such an approach, eg the safety concerns of experiments designed by learners, the availability of the physical apparatus, the amount of supervision that the teacher can realistically provide to a number of learners doing different experiments.

If we take the scenario into a virtual environment, some of the limitations no longer apply. For instance, there should not be any real concern of safety even if the experiment is explosive. The virtual explosion will hurt nobody and cause no real damage. The availability of the apparatus is now only limited to the computer resources available. The same virtual apparatus can be used by as many students as allowed by the software license agreement. Since the safety issue is no longer of prime importance, the supervision shifts from ensuring safety of the students to more educationally oriented objectives such as the feasibility of the experiments, the actual learning outcome, the motivation level of the learners and scaffolding support to the learner.

4. The Virtual Apparatus Model for Authoring of Virtual Experiment

The virtual apparatus model is based on the component model in software engineering. Virtual apparatus are software components that can be dynamically combined together to create a virtual experiment. There are three major components in this model:

ï virtual apparatus

ï virtual experiment work bench and

ï the software glue.

In technical terminology, the virtual apparatus are Component software, the virtual workbench is the components container while the software glue is the scripting language available to that software platform. The current implementation will be based on Java and the Microsoft's ActiveX technology using Internet Explorer 3.0 as the default web browser. However it is just a matter of time for Java Beans from Sun Microcomputer Systems or other component software vendors to come up with alternative solutions which can offer similar functions. The virtual apparatus, however, should meet additional requirements if we are aiming at a reusable, friendly and workable model.

The virtual apparatus should share some of the qualities people are already familiar with in physcial apparatus, in particular they can:

ï be manipulated easily,

ï inter-operate,

ï assemble together to form new experiments,

ï reflect behaviours of the real world.

Teachers designing a virtual experiment would typically create a virtual experiment work bench which is a web-browser supporting this technology (currently, Microsoft Internet Explorer 3.0). A number of virtual apparatus would be selected from some repository and put on the work bench.

Some of these virtual apparatus would be visible and hence will be rendered by the browser software. Others would be invisible and used in other ways as described below. Scripts (in JavaScript or VB script) would then be written to link the apparatus events together.

The experiment workbenches can be saved as html web pages together with some other textual information and can be accessed by learners. When the learner opens such a web page, the web-browser would download the required virtual apparatus if they were not already on the client machine. The learner interacts with the virtual experiment by clicking, dragging and so on. This interaction fires up events by the virtual apparatus. The events are passed to the scripting language and processed. Other virtual apparatus may receive messages from the script and respond accordingly, creating the necessary response to the learner's interactions.

5. Software Requirements for virtual apparatus

Some of the requirements appearing in the following list are already implemented as part of the Java/ActiveX specification. They are listed here for completeness:

ï Each virtual apparatus should be a logical computational unit, a file by itself at this moment. To allow and encourage reuse of the same virtual apparatus, the apparatus should not be unnecessarily dependent upon other virtual apparatus. Each of the virtual apparatus shouldsupport use on its own.

ï A virtual apparatus should have a functional part (that mimics the behaviour of a real-world counterpart) and for those virtual apparatus that are visible, a visual interface (the graphical representation of the apparatus). The functional parts are public functions exposed by the software which the script can use. The initial behaviour of the virtual apparatus should be controlled by a set of parameters set by the virtual experimental work bench during initialisation.

ï A virtual apparatus should expose all its public methods and variables for easy authoring in authoring mode. In run mode, this feature must be turned off. However, there is no automatic method of doing this. Our suggestion is to use a software key. If the key is present, the virtual apparatus should recognise that it is in authoring mode, otherwise it is in run mode.

ï One of the (standard) methods should provide a comprehensive description of the functions of the virtual apparatus. This requirement is necessary to dynamically create a search interface for any repository of virtual apparatus.

ï A virtual apparatus should be able to raise events to the virtual experiment work bench and accept calls after initialisation.

The virtual apparatus will be implemented as a "class", in the Java programming language, in that it describes the visual interface and behaviour of a type of apparatus. The local machine should be able to instantiate working copies of the apparatus from the same file. This is again advantageous to the network model we are referring to. When the same class of apparatus is used more than once in an experiment, the client machine needs only to download one copy of the apparatus and the virtual experiment work bench will create various copies of the apparatus locally without incurring further network traffic.

The virtual experiment work bench is a container for the virtual apparatus and should be able to communicate with the virtual apparatus at two levels: receiving events generated by the virtual apparatus and sending commands (or altering the parameters of the virtual apparatus) after initialisation. Currently ActiveX of Internet Explorer 3.0 supports this requirement.

The observable experiment parameters are not set by the virtual apparatus, but by controlling how the virtual apparatus behaves. This is done by scripting. The scripting language can set and/or alter the properties of the virtual apparatus, respond to events initiated by some other virtual apparatus and pass messages on to other virtual apparatus. By using simple scripting language, such as VB script (which is a subset of the Visual Basic Language), teachers can assemble a virtual experiment more easily than creating one ab initio.

6. Availability

For the "virtual apparatus" to go from concept to becoming a viable solution, it must undergo detailed design and development and become widely accepted. The creation of an automatic central registry would ease the distribution. The central registry would provide the following services:

ï categorise the virtual apparatus to facilitate searching

ï provide developer information

ï provide version control

ï digitally shrink-wrap the virtual apparatus. By shrink-wrapping the apparatus, the user is guaranteed that the file(s) which are downloaded have not been modified or virus affected subsequent to submission by the original developer.

ï provide license control so that the developer can control the distribution of the virtual apparatus and may be rewarded for thiseffort.

At the time of writing this paper, Microsoft announced the general availability of J++, its version of Java programming which also supports the ActiveX specification. We envisage that by the time this paper is presented, we will have a working demonstration of the ideas presented in this paper.

7. Conclusion

It is clear that there will be a continuing demand for authoring virtual experiments for delivery via the world wide web and that methodologies for lowering the complexity of doing this are required. In the paper, we put forth a concept which is made feasible by recent technology but requires further development and collaboration to be fully implemented.

The virtual apparatus model allows teachers to take ownership of the virtual experiments they create without requiring them to invest heavily in understanding a fast changing technology. Similarly, the computer professionals can take ownership of creation of the virtual apparatus. This aspect of the model addresses the "not-invented-here" syndrome by acknowledging the professional value and expertise of both groups.

The success of such a model depends on whether the model can give rise to practical solution that is acceptable to the teaching professionals. It is our intention to start building a repository of virtual apparatus and make them available to anybody interested.


Bothun G (1996) Virtual Laboratory. [http://jersey.uoregon.edu/vlab/]

Eriksson H (1996) Control The Nuclear Power Plant (Demonstration). [http://www.ida.liu.se/~her/npp/demo.html]

Johnston W (1994) Virtual Frog Dissection Kit. [http://www-itg.lbl.gov/vfrog/]

Kinzie M (1994) The interactive frog dissection.


US National Library of Medicine (1995) The visible human project. [http://www.nlm.nih.gov/research/visible/visible_human.html]

Kaufman A (1995) 3D Virtual Colonoscopy. [http://www.cs.sunysb.edu/~vislab/start_colonoscopy.html]