The scope of software visualization tools which exist for the navigation, analysis and presentation of software information varies widely. One class of tools, which we refer to as software exploration tools, provide graphical representations of software structures linked to textual views of the program source code and documentation. This paper describes a hierarchy of cognitive issues which should be considered during the design of a software exploration tool. The hierarchy of cognitive design elements is derived through the examination of program comprehension cognitive models. Examples of how existing tools address each of these issues are provided.

In this paper, we explore the question of whether program understanding tools enhance or change the way that programmers understand programs. The strategies that programmers use to comprehend programs vary widely. Program understanding tools should enhance or ease the programmer's preferred strategies, rather than impose a fixed strategy that may not always be suitable. We present observations from a user study that compares three tools for browsing program source code and exploring software structures. In this study, 30 participants used these tools to solve several high-level program understanding tasks. These tasks required a broad range of comprehension strategies. We describe how these tools supported or hindered the diverse comprehension strategies used.

This paper describes the SHriMP visualization technique for seamlessly exploring software structure and browsing source code, with a focus on effectively assisting hybrid program comprehension strategies. The technique integrates both pan+zoom and fisheye-view visualization approaches for exploring a nested graph view of software structure. The fisheye-view approach handles multiple focal points, which are necessary when examining several subsystems and their mutual interconnections. Source code is presented by embedding code fragments within the nodes of the nested graph. Finer connections among these fragments are represented by a network that is navigated using a hypertext link-following metaphor. SHriMP combines this hypertext metaphor with animated panning and zooming motions over the nested graph to provide continuous orientation and contextual cues for the user. The SHriMP tool is currently being evaluated in several user studies. Observations of users performing program understanding tasks with the tool are discussed.

The Rigi reverse engineering system provides tNo con-trasting approaches for presenting software structures in its graph editor. The first displays the struc-tures through multiple, individual NindoNs. The sec-ond (neNer) approach, Simple Hierarchical Multi-Perspective (SHriMP) views, employs fisheye views of nested graphs. We compare and contrast these tNo in-terfaces for visualizing software graphs, and provide re-sults from user experiments.

This paper describes a multi-perspective software visualization environment, SHriMP, which combines single view and multi-view techniques to support software exploration at both the architectural and source code levels. SHriMP provides three different views: a primary nested view and two subsidiary views. The primary nested view employs fisheye views of nested graphs, provides contextual cues, and supports general exploration activities. In SHriMP, subsidiary views exist as a searching tool and a relation tracer. These views complement each other and allow programmers to examine a software system from multiple perspectives.

During maintenance activities, the availability of integrated conceptual views that present software at dierent levels of abstraction, from software architecture to control and data ow relations at code level, is fundamental to understand and modify legacy systems. This paper presents CANTO, a comprehensive program understanding and maintenance environment which integrates ne grained information with architectural views extracted from source code, giving the user control on what is being computed by analyses. The capabilities and usefulness of CANTO are illustrated with reference to a real understanding and maintenance task. 1

This paper describes a structured tool demonstration, a hybrid evaluation technique that combines elements from experiments, case studies, and technology demonstrations. Developers of program understanding tools were invited to bring their tools to a common location to participate in a scenario with a common subject system. Working simultaneously, the tool teams were given reverse engineering tasks and maintenance tasks to complete on an unfamiliar subject system. Observers were assigned to each team to find out how useful the observed program comprehension tool would be in an industrial setting. The demonstration was followed by a workshop panel where the development teams and the observers presented their results and findings from this experience.

Software programs, especially legacy programs, are often large, complex and poorly documented. To maintain these programs software engineers require a variety of efficient analytical tools. Some software maintenance tools use visualizations (i.e. graphical views) to communicate information about software systems. Although many software visualization tools exist, the majority of them are not very effective in practice. Part of the problem is that they are designed in an ad hoc manner, with little empirical evaluation. They are often criticized because they try to force programmers to use a specific approach to understanding software rather than supporting their own approaches. The result is that current software visualization tools do not play as big a role in industry as was anticipated by some researchers. The tools that are used are very basic, consisting of mainly text editors and searching features. With increasingly fast computing platforms, there is great potential for the use of...

Frequently large knowledge bases are represented by graphs. Many visualization tools allow users or other applications to interact with and adjust the layouts of these graphs. One layout adjustment problem is that of showing more detail without eliding parts of the graph. Approaches based on a fisheye lens paradigm seem well suited to this task. However, many of these techniques are non-trivial to implement and their distortion techniques often cannot be altered to suit different graph layouts. When distorting a graph layout, it is often desirable to preserve various properties of the original graph in an adjusted view. Pertinent properties may include straightness of lines, graph topology, orthogonalities and proximities. However, it is normally not possible to preserve all of the original properties of the graph layout. The type of layout and its application should be considered when deciding which properties to preserve or distort. This paper describes a fisheye view algori...

Despite their potential applications in software comprehension, it appears that dynamic visualisation tools are seldom used outside the research laboratory. This paper presents an empirical evaluation of five dynamic visualisation tools- AVID, Jinsight, jRMTool, Together ControlCenter diagrams and Together ControlCenter debugger. The tools were evaluated on a number of general software comprehension and specific reverse engineering tasks using the HotDraw objectoriented framework. The tasks considered typical comprehension issues, including identification of software structure and behaviour, design pattern extraction, extensibility potential, maintenance issues, functionality location, and runtime load. The results revealed that the level of abstraction employed by a tool affects its success in different tasks, and that tools were more successful in addressing specific reverse engineering tasks than general software comprehension activities. It was found that no one tool performs well in all tasks, and some tasks were beyond the capabilities of all five tools. This paper concludes with suggestions for improving the efficacy of such tools. 1.