ADT Extends Probe

Finally, let us assume that we do not have an implementation for AVL-tree, but we would like to create one for our own purposes. This might be the case, for example, if we would like to animate an AVL tree of our own. The easiest way to implement and visualize an AVL-tree is to reuse the binary search tree probe and to change its behavior properly. For example, one can inherit the existing binary search tree and override its insert and delete methods to keep the tree balanced.

4 Discussion

Algorithm simulation provides lecturers as well as students a valuable aid for demonstrating and sur-veying the working of basic algorithms because no user written code is needed. Moreover, the instru-ments that are capable of visualization and simulation of user’s own code greatly extend the learning possibilities.

Even though educational software is the main application area for Matrix, it is obvious that similar tools can be applied also to other areas. These instruments can be used for testing purposes or visual debugging in software engineering. However, the more application areas there are involved the more flexibility is needed to meet the overall requirements. Our strategy, in this sense, is to support as many techniques as possible. Moreover, our research aims at new techniques and specification styles, such as algorithm simulation.

Even though some techniques are not fully supported at the moment, the Matrix framework is at least capable of adopting them with little or no effort. Thus, it is flexible enough to be extended further in terms of fast prototyping. We believe that this is the way we can keep the framework live enough also for further research. Of course, real applications for special areas are better implemented from the scratch, but at that point it should be clear which techniques to use.

From this point of view, it is obvious that there is not just one technique that could dominate the others. The invasive methods have their applications in education as stated by Stasko (1997).

However, they cannot be applied to software engineering, if effortless techniques are required. The interface typing can produce arbitrary complex structural visualizations, but lacks the ability to store the animation or reverse its temporal direction. Probing can fix this problem, but requires inheritance.

Annotation can be applied to automatic code animation, but it has its weaknesses as it is an invasive

method. Thus, by supporting multiple techniques and specification styles the system can allow the visualizer to choose the technique used, so that it would be the most suitable for the specified case.

4.1 Future

Obviously, the range of different techniques can be extended even further. At the moment, the research is aiming at even more effortless visualizations. One possible area of development is the intelligent systems that are capable of concept visualizations of arbitrary data structures. The idea is not com-pletely new, but the Java language provides new powerful tools to implement the technique. From Matrix point of view this could mean a process where the conceptual displays are generated without the need to implement any of the interfaces.

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