isbn9789526046266

another panel. A better solution in the future might bring explanatory texts closer to where the VPS
action is.
Another limitation of UUhistle that is highlighted by the split-attention and modality effects is its lack
of support for the auditory channel. The human capacity to receive sensory information is very limited,
and one of the few known ways to alleviate the problem is to use visuals and sound simultaneously. The
current failure of UUhistle to do so must be viewed as something to improve upon.
The overall effects of UUhistle’s user interface on cognitive load are unknown at present.
Conclusions on usability
UUhistle’s usability appears fairly good.
The analysis of cognitive dimensions suggests that the design of UUhistle’s VPS exercises suits their
intended purpose. The laborsome, viscous nature of some interactions is perhaps UUhistle’s greatest
usability challenge from the cognitive dimensions point of view. The split-attention effect is another
cause for concern. There are many small problems that we are aware of and UUhistle is, of course, still a
work in progress.
Ultimately, UUhistle’s usability depends on how learners use it. We have conducted no formal usability
studies. However, thousands of students have succeeded in using the system and most have found it easy
enough to use. I present some results from an opinion survey in Chapter 20.
An external evaluation
This chapter has presented our own analysis of UUhistle. In a recent independent review of visualization
systems, Gondi (2011) evaluated a visualization example in UUhistle against nine best practices identified
in the literature. A 2–3–4-tree visualization in UUhistle was found to support eight of these practices,
namely, support for flexible execution control, providing a context for users to interpret the visualization
(such as a textual description), providing multiple views or representations, allowing user-specified data
sets, showing the source code of what is being visualized, suitability for use as a lecture aid, suitability
for self-study, and suitability for debugging.
The ninth best practice, having students answer questions or make predictions, was apparently not
present in the particular example evaluated by Gondi. As the reader will know by now, UUhistle does, of
course, very much support such modes of interaction as well.
In Part IV, I have presented visual program simulation and a supporting piece of software as the outcomes
of what I hope appears to be a rational and logical process.
In a keynote address at the Koli Calling 2010 conference on computing education research, Michael
Kölling 10 remarked that the design of pedagogical software by computing educators is often informed
by gut feeling, but that this is not bad – gut feelings are important and useful. Nevertheless, Kölling
reminded us, with reference to Parnas’s famous article A Rational Design Process: How and Why to Fake
It, it is worthwhile to rationalize our design process and to relate it to theory.
According to Parnas, no software project, past, present, or future, proceeds in the ‘rational’ way, but
we can still make an effort to approach rationality and to document our software as if we had followed
the ideal process: the documentation should help the reader to understand what we have created, not to
relive the creation process. “It is very hard to be a rational designer; even faking that process is quite
difficult. However, the result is a product that can be understood, maintained, and reused.” (Parnas and
Clements, 1986, p. 256)
Parnas wrote about designing and documenting software artifacts and their modules. My concern
in this thesis is not one of software design in Parnas’s sense, but the design and documentation of a
software-supported pedagogical approach. This work on visual program simulation has not followed a
rational, well defined sequence of steps, although this thesis may sometimes portray it as such. The work
has been informed throughout by a complex interweaving of gut feeling, literature, and emerging empirical
10 Say this five times fast: collected colleagues of Kölling at Koli Calling.
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