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.

Well-designed object-oriented programs typically consist of a few key classes that work tightly together to provide the bulk of the functionality. As such, these key classes are excellent starting points for the program comprehension process. We propose a technique that uses webmining principles on execution traces to discover these important and tightly interacting classes. Based on two medium-scale case studies – Apache Ant and Jakarta JMeter – and detailed architectural information from its developers, we show that our heuristic does in fact find a sizeable number of the classes deemed important by the developers.

Large software projects often require a programmer to make changes to unfamiliar source code. This paper presents the results of a formative observational study of seven professional programmers who use a conventional development environment to update an unfamiliar implementation of a commonly known video game. We describe several usability problems they experience, including keeping oriented in the program’s source text, maintaining the number and layout of open text documents and relying heavily on textual search for navigation. To reduce the cost of transferring knowledge about the program among developers, we propose the idea of wear-based filtering, a combination of computational wear and social filtering. The development environment collects interaction information, as with computational wear, and uses that information to direct the attention of subsequent users, as with social filtering. We present sketches of new visualizations that use wear-based filtering and demonstrate the feasibility of our approach with data drawn from our study.

We present conditioned slicing as a general slicing framework for program comprehension. A conditioned slice consists of a subset of program statements which preserves the behavior of the original program with respect to a set of program executions. The set of initial states of the program that characterize these executions is specified in terms of a first order logic formula on the input variables of the program. Conditioned slicing allows a better decomposition of the program giving the maintainer the possibility to analyze code fragments with respect to different perspectives. We also show how slices produced with traditional slicing methods can be reduced to conditioned slices. Conditioned slices can be identified by using symbolic execution techniques and dependence graphs. 1 Introduction The comprehension of an existing software system consumes from 50% up to 90% of its maintenance time. Comprehending a software system can be defined as the process of abstracting higher level d...

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.

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development. Service-orientation allows organisations to rapidly form new software applications dynamically to meet changing business needs, thus alleviating the problems of software evolution that occur with traditional applications. The largest of these problems is understanding the existing software before it can be changed. In this article, we look a little further ahead towards the automated construction of service-oriented software, discussing software comprehension in the context of service-orientation and identifying some new issues that will need to be overcome. We draw the conclusion that, whilst service-orientation certainly helps to solve some aspects of the evolution problem, software comprehension takes a new and potentially more challenging role.

Despite significant existing empirical work, little is known about the specific kinds of questions programmers ask when evolving a code base. Understanding precisely what information a programmer needs about the code base as they work is key to determining how to better support the activity of programming. The goal of this research is to provide an empirical foundation for tool design based on an exploration of what programmers need to understand about a code base and of how they use tools to discover that information. To this end, we undertook two qualitative studies of programmers performing change tasks to medium to large sized programs. One study involved newcomers working on assigned change tasks to a mediumsized code base. The other study involved industrial programmers working on their own change tasks to code with which they had experience. The focus of our analysis has been on what information a programmer needs to know about a code base while performing a change task and also on how they go about discovering that information. Based on a systematic analysis of the data from these user studies as well as an analysis of the support that current programming tools provide for these activities, this research makes four key contributions: (1) a catalog of 44 types of questions programmers ask, (2) a categorization of those questions into four categories based on the kind and scope of information needed to answer a question, (3) a description of important context for the process of answering questions, and (4) a description of support that is missing from current programming tools.