About PADs
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Overview
Grading | Combining
| Code
General features
PADs are interactive Java applets that provide a wide range of ways to
represent data and evaluate the correctness of those representations.
The all offer a fair number of options for
setting criteria for evaluation, changing appearances and functions, and
getting them to function together.
Grading
PADs have an internal grading engine so that no additional code needs to
be writing to have them automatically evaluate graphs and diagrams.
Grading options can be set for a whole range of qualitative or quantitative
evaluation. The kinematics PADs (EquationPAD,
GraphPAD, MotionPAD,
StrobePAD, TablePAD,
VideoPAD) accomplish this by fitting a function
to the data points, and then compare the fit parameters to values specified
in the parameters of the applet. This has a number of major advantages.
First, certain features of a graph or diagram can be selected while others
ignored, such as expecting a specific slope of the graph but accepting
any starting point. Second, by setting the tolerances appropriate,
qualitative or quantitative evaluation can be achieved, e.g. requiring
a merely a positive slope or requiring it to be 1.5 +/- 0.1. Third,
when there are multiple data points in a PAD, having one slightly off from
the correct position will have a reduced effect on the grading.
Forth, a question coder needs to know no Java or programming, simply how
to specify the accepted values of each parameter. Fifth, the six
different applets use the very same internal representation and evaluation
routines, so there is less to learn when moving from one to another.
If greater security is desired, the webserver optionally could supply the
PAD with no information about what to consider correct and instead use
a string representation of the status returned by the PAD to evaluate.
Combining
PADs are modular and are designed to communicate with each other.
Any PAD can broadcast changes in its data to any other PAD on a web page,
so when a user clicks on a point in VideoPAD, the time and position information
can be automatically inserted into a GraphPAD or TablePAD on the same page.
Also, the status of another PAD can be used in the criteria for grading,
for example requiring the intercept of a line segment on a velocity graph
be the same as the slope for the corresponding segment on a position graph.
Code
PADs are Java applets written in Java 1.1, "old" technology that is present
in every major browsers, even 4.x generation Netscape and Internet Explorer.
This means no downloads or plug-ins to make them work. PADs can be scripted
using JavaScript, but that is unnecessary for normal use. All the
flexible options are specified by the use of the <PARAM> parameter tags.
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