Tool Building: Web-based Linear Algebra Modules - What is [i]JavaSketchpad[/i]?

What we have done here is use an existing software product, The Geometer's Sketchpad (Jackiw, 2001), but in a way for which it was not originally designed. It is intended for geometric constructions, but we have used the geometric basis and the interactivity to build our tools. Moreover, the current version has an applet, JavaSketchpad, which allows most Sketchpad code to be run on a Java-enabled web browser. So we now have true platform- and software-independence as well. The tools in this article download the JavaSketchpad applet and the accompanying code in a way that is transparent to the user. The only skill required is use of a web browser -- a nearly universal skill these days.

According to Key Curriculum Press (2001, p. 231), "JavaSketchpad is a Sketchpad extension that allows you to place simple sketches inside web pages you publish on the Internet." This allows an Internet user to interact with the elements of the sketch by dragging points and pressing action buttons even if they do not have local access to Sketchpad. JavaSketchpad is a scaled-down version of Sketchpad and therefore not capable of all the constructions generally available through The Geometer's Sketchpad 4.01.

Two elements are necessary to build a JavaSketchpad in order to interact with the dynamic sketch. The first element is the HTML file that contains the descriptions necessary to render the web page, as well as the descriptions of the geometric construction and associated action buttons included in the sketch. The second element is the JavaSketchpad applet. This applet differs from that of a plug-in which must be installed by the user prior to operating a particular application. The applet is held in the same directory as the HTML file and is downloaded at the same time the HTML file is accessed from the visitor's machine. In particular, "The applet -- a separate set of files -- provides the functionality that interprets this description (of the geometric construction), displays the figure in your visitor's browsers, and lets them interact with it" (Key Curriculum Press, 2001, p. 232). This simplifies the transfer and allows the user to interact seamlessly with the sketch without having to first download and install a plug-in.

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