Page 3 - Physlets and Open Source Physics for Quantum Mechanics:

The Physlet paradigm, an example of which is shown in Figure 1, is based on the
Model-View-Control (MVC) design pattern which is one of the most successful software
architectures ever invented. The model maintains data and provides methods by which
that data can change; the control gives the user the ability to interact with the model
using the keyboard and the mouse; and the view presents a visual representation of
the model’s data. Java is ideal for the implementation of models and views because
these objects are often complex and computational speed is important. But since the
control object is accessed infrequently and should be customizable, it can be
implemented differently. A scripting language such as JavaScript embedded into an
HTML document provides an ideal solution. The advantage of using JavaScript and
HTML to control a model and its views is that a common user interface can be created
to ease the learning curve across pedagogical contexts. This unique approach has
contributed to the success and wide adoption of Physlets. For example, a Google
search on “Physlets” returns over 12,000 Web pages.

Open Source Physics

Figure 2: An OSP program, QMSuperpositionApp,
used to depict a two-state superposition for the
quantum-mechanical harmonic oscillator. The
visualization (the view) is shown on the left while the
OSP control is shown on the right. One can edit
animation parameters by typing in the parameter
fields. These parameter values can also be saved and
loaded using an XML file as shown in Figure 3.

While Physlets are in many ways ‘open,’ they are not open source. As a consequence,
the underlying Java code is inaccessible. This approach works for general-purpose
applications, but fails for more sophisticated one-of-a-kind simulations that require
advanced discipline-specific expertise, such as those for quantum mechanics. Users
and developers of these types of programs often have specialized curricular needs that
can only be addressed by having access to the source code. However, anyone who
has ever written a program in Java knows that writing code for creating buttons, text
fields, and graphs can be tedious and time consuming. The Open Source Physics
(OSP) project [20] solves this problem by providing a consistent object-oriented library
of Java components (OSP libraries are based on Swing and Java 1.4) for anyone
wishing to write their own programs.

Open Source Physics curricular material is written in Java and distributed using internet
technologies. Although we distribute source code under the GNU GPL license, the