Okanović, Dušan; Beck, Samuel; Merz, Lasse; Zorn, Christoph; Merino, Leonel; van Hoorn, André; Beck, Fabian: Can a Chatbot Support Software Engineers with Load Testing? Approach and Experiences. In: ICPE 2020 Industry and Experience Track (to appear). 2020. PDF Citation Abstract Details
Even though load testing is an established technique to assess load-related quality properties of software systems, it is applied only seldom and with questionable results. Indeed, configuring, executing, and interpreting results of a load test require high effort and expertise. Since chatbots have shown promising results for interactively supporting complex tasks in various domains (including software engineering), we hypothesize that chatbots can provide developers suitable support for load testing.
In this paper, we present PerformoBot, our chatbot for configuring and running load tests. In a natural language conversation, PerformoBot guides developers through the process of properly specifying the parameters of a load test, which is then automatically executed by PerformoBot using a state-of-the-art load testing tool. After the execution, PerformoBot provides developers a report that answers the respective concern. We report on results of a user study that involved 47 participants, in which we assessed our tool's acceptance and effectiveness. We found that participants in the study, particularly those with a lower level of expertise in performance engineering, had a mostly positive view of PerformoBot.
Mumtaz, Haris; Latif, Shahid; Beck, Fabian; Weiskopf, Daniel: Exploranative Code Quality Documents. In: IEEE Transactions on Visualization and Computer Graphics, to appear, Vol 26 (2020) No 1. PDF Citation Abstract Details
Good code quality is a prerequisite for efficiently developing maintainable software. In this paper, we present a novel approach to generate exploranative (explanatory and exploratory) data-driven documents that report code quality in an interactive, exploratory environment. We employ a template-based natural language generation method to create textual explanations about the code quality, dependent on data from software metrics. The interactive document is enriched by different kinds of visualization, including parallel coordinates plots and scatterplots for data exploration and graphics embedded into text. We devise an interaction model that allows users to explore code quality with consistent linking between text and visualizations; through integrated explanatory text, users are taught background knowledge about code quality aspects. Our approach to interactive documents was developed in a design study process that included software engineering and visual analytics experts. Although the solution is specific to the software engineering scenario, we discuss how the concept could generalize to multivariate data and report lessons learned in a broader scope.
Sancho-Chavarría, Lilliana; Gómez-Soza, Carlos; Beck, Fabian; Mata-Montero, Erick: Diaforá: A Visualization Tool for the Comparison of Biological Taxonomies. In: Proceedings of the Latin America High Performance Computing Conference. Springer, 2019, p. 423-437. doi:10.1007/978-3-030-41005-6_29 PDF Citation Abstract Details
We address the problem of visualizing differences between two versions of a biological taxonomy. Given the dynamics of the taxonomic work, taxonomists are often faced with alternative versions of a taxonomy that need to be reconciled. Nevertheless, visual comparison of hierarchies is an open problem that involves several difficult challenges in Visual Analytics. First, how to display not one but two possibly large taxonomies on a fixed-size screen. Second, how to highlight all differences between the two taxonomies. We present Diaforá, an interactive tool that infers and visualizes the differences. Automatic inference is achieved by incorporating taxonomy rules to identify operations such as merging, splitting, and renaming of taxa, among others. Highlighting of differences is accomplished by using the edge drawing technique, which has been enhanced with a number of features suggested by users of a prototype version. Diaforá has been implemented and tested with real world taxonomies such as Bryozoa and Annelida as well as with artificial taxonomies.
Munz, Tanja; Burch, Michael; van Benthem, Toon; Poels, Yoeri; Beck, Fabian; Weiskopf, Daniel: Overlap-free Drawing of Generalized Pythagoras Trees for Hierarchy Visualization. In: 2019 IEEE Visualization Conference (VIS), Short Papers. IEEE, 2019, p. 251-255. doi:10.1109/VISUAL.2019.8933606 PDF Citation Abstract Details
Generalized Pythagoras trees were developed for visualizing hierarchical data, producing organic, fractal-like representations. However, the drawback of the original layout algorithm is visual overlap of tree branches. To avoid such overlap, we introduce an adapted drawing algorithm using ellipses instead of circles to recursively place tree nodes representing the subhierarchies. Our technique is demonstrated by resolving overlap in diverse real-world and generated datasets, while comparing the results to the original approach.
Sandoval Alcocer, Juan Pablo; Beck, Fabian; Bergel, Alexandre: Performance Evolution Matrix: Visualizing Performance Variations along Software Versions. In: Proceedings of the 2019 Working Conference on Software Visualization. IEEE, 2019. doi:10.1109/VISSOFT.2019.00009 PDF Citation Abstract Details
Software performance may be significantly affected by source code modifications. Understanding the effect of these changes along different software versions is a challenging and necessary activity to debug performance failures. It is not sufficiently supported by existing profiling tools and visualization approaches. Practitioners would need to manually compare calling context trees and call graphs. We aim at better supporting the comparison of benchmark executions along multiple software versions. We propose Performance Evolution Matrix, an interactive visualization technique that contrasts runtime metrics to source code changes. It combines a comparison of time series data and execution graphs in a matrix layout, showing performance and source code metrics at different levels of granularity. The approach guides practitioners from the high-level identification of a performance regression to the changes that might have caused the issue. We conducted a controlled experiment with 12 participants to provide empirical evidence of the viability of our method. The results indicate that our approach can reduce the effort for identifying sources of performance regressions compared to traditional profiling visualizations.
Received the VISSOFT 2019 Best Paper Award
Sandoval Alcocer, Juan Pablo; Camacho Jaimes, Harold; Costa, Diego; Bergel, Alexandre; Beck, Fabian: Enhancing Commit Graphs with Visual Runtime Clues. In: Proceedings of the 2019 Working Conference on Software Visualization. IEEE, 2019. doi:10.1109/VISSOFT.2019.00012 PDF Citation Abstract Details
Monitoring software performance evolution is a daunting and challenging task. This paper proposes a lightweight visualization technique that contrasts source code variation with the memory consumption and execution time of a particular benchmark. The visualization fully integrates with the commit graph as common in many software repository managers. We illustrate the usefulness of our approach with two application examples. We expect our technique to be beneficial for practitioners who wish to easily review the impact of source code commits on software performance.
Latif, Shahid; Su, Kaidie; Beck, Fabian: Authoring Combined Textual and Visual Descriptions of Graph Data. In: EuroVis 2019 - Short Papers. The Eurographics Association, 2019. doi:10.2312/evs.20191180 PDF Citation Abstract Details
The interactive linking of text and visualizations supports easy and guided exploration of information and results in a coherent
reducing the effort by providing a declarative syntax. However, these approaches either do not support the interactive linking
of text and visualizations or require advance programming skills to establish this linking. Targeting a specific type of data i.e.,
graph data, we introduce an approach that uses a declarative syntax to produce interactive documents and requires little to no
programming. Based on the user specifications in an HTML file, the system queries the database to retrieve subgraphs and link
them to the relevant text fragments. The resulting document consists of a node-link diagram and text; the two representations
are closely linked via interactions and word-sized graphics, and provide an active reading experience.
Mumtaz, Haris; van Garderen, Mereke; Beck, Fabian; Weiskopf, Daniel: Label Placement for Outliers in Scatterplots. In: EuroVis 2019 - Short Papers. The Eurographics Association, 2019. doi:10.2312/evs.20191161 PDF Citation Abstract Details
In many application scenarios, outliers can be associated with specific importance for various reasons. In such cases, labeling outliers is important to connect them to the actual semantics of the respective entity. In this paper, we present a cost-based greedy approach that places labels with outliers within scatterplots. The approach uses a search strategy to find the position that represents the least cost to place labels. Our approach can also produce different labeling outcomes by adjusting the weights of the criteria of the cost function. We demonstrate our approach with scatterplots produced from object-oriented software metrics, where outliers often relate to bad smells in the software.
Latif, Shahid; Beck, Fabian: Interactive Map Reports Summarizing Bivariate Geographic Data. In: Visual Informatics, Vol 3 (2019) No 1, p. 27-37. doi:10.1016/j.visinf.2019.03.004 PDF Citation Abstract Details
Bivariate map visualizations use different encodings to visualize two variables but comparison across multiple encodings is challenging. Compared to a univariate visualization, it is significantly harder to read regional differences and spot geographical outliers. Especially targeting inexperienced users of visualizations, we advocate the use of natural language text for augmenting map visualizations and understanding the relationship between two geo-statistical variables. We propose an approach that selects interesting findings from data analysis, generates a respective text and visualization, and integrates both into a single document. The generated reports interactively link the visualization with the textual narrative. Users can get additional explanations and have the ability to compare different regions. The text generation process is flexible and adapts to various geographical and contextual settings based on small sets of parameters. We showcase this flexibility through a number of application examples.
Okanović, Dušan; van Hoorn, André; Zorn, Christoph; Beck, Fabian; Ferme, Vincenzo; Walter, Jürgen: Concern-driven Reporting of Software Performance Analysis Results. In: Companion of the 2019 ACM/SPEC International Conference on Performance Engineering. ACM, 2019, p. 1-4. doi:10.1145/3302541.3313103 PDF Citation Abstract Details
State-of-the-art approaches for reporting performance analysis results rely on charts providing insights on the performance of the system, often organized in dashboards. The insights are usually data-driven, i.e., not directly connected to the performance concern leading the users to execute the performance engineering activity, thus limiting the understandability of the provided result. A cause is that the data is presented without further explanations.
To solve this problem, we propose a concern-driven approach for reporting of performance evaluation results, shaped around a performance concern stated by a stakeholder and captured by state-of-the-art declarative performance engineering specifications. Starting from the available performance analysis, the approach automatically generates a customized performance report providing a chart- and natural-language-based answer to the concern. In this paper, we introduce the general concept of concern-driven performance analysis reporting and present a first prototype implementation of the approach. We envision that, by applying our approach, reports tailored to user concerns reduce the effort to analyze performance evaluation results.
Latif, Shahid; Beck, Fabian: VIS Author Profiles: Interactive Descriptions of Publication Records Combining Text and Visualization. In: IEEE Transactions on Visualization and Computer Graphics, Vol 25 (2019) No 1, p. 152-161. doi:10.1109/TVCG.2018.2865022 PDF Citation Abstract Details
Publication records and collaboration networks are important for assessing the expertise and experience of researchers. Existing digital libraries show the raw publication lists in author profiles, whereas visualization techniques focus on specific subproblems. Instead, we look at publication records from various perspectives mixing low-level publication data with high-level abstractions and background information. This work presents VIS Author Profiles, a novel approach to generate integrated textual and visual descriptions to highlight patterns in publication records. We leverage template-based natural language generation to summarize notable publication statistics, evolution of research topics, and collaboration relationships. Seamlessly integrated visualizations augment the textual description and are interactively connected with each other and the text. The underlying publication data and detailed explanations of the analysis are available on demand. We compare our approach to existing systems by taking into account information needs of users and demonstrate its usefulness in two realistic application examples.
Latif, Shahid; Beck, Fabian: Visually Augmenting Documents With Data. In: Computing in Science & Engineering (2018), p. 96-103. doi:10.1109/MCSE.2018.2875316 PDF Citation Abstract Details
“A picture is worth a thousand words” is a famous English saying. It is true in many cases, because a complex idea or data can be simply conveyed through the use of a single static image or diagram. Therefore, inclusion of graphics and visualizations in scientific texts has been an important aspect ever since researchers started publishing articles. Conventional writing styles allow researchers to provide images, graphs, and tables to enhance the readability and understandability of the text, but usually, these large-scale images need to be placed at a slightly different location from the relevant text, either on the same page or on the next pages. This far-off placement of graphics forces readers to switch their attention between text and graphics, which can cause a split-attention effect, thereby increasing the cognitive effort to comprehend the information.
Tarner, Hagen; Frick, Veit; Pinzger, Martin; Beck, Fabian: Exploring Visual Comparison of Multivariate Runtime Statistics. In: 9th Symposium on Software Performance 2018. Hildesheim 2018. PDF Citation Abstract Details
To understand program behavior or find performance bottlenecks in their software, developers need tools to efficiently compare runtime statistics collected across multiple executions. As there is a variety of useful metrics, a good visualization needs to be able to handle multivariate data and highlight the most important differences between multiple versions. We identify three scenarios for the comparison of execution-relevant changes, and explore possible visualizations of the gathered multivariate runtime statistics.
Agarwal, Shivam; Bernard, Jürgen; Beck, Fabian: Computer-supported interactive assignment of keywords for literature collections. In: Proceedings of the 1st International Workshop on Machine Learning from User Interaction for Visualization and Analytics at IEEE VIS. 2018. PDF Citation Abstract Details
A curated literature collection on a specific topic helps researchers to find relevant articles quickly. Assigning multiple keywords to each article is one of the techniques to structure such a collection. But it is challenging to assign all the keywords consistently without any gaps or ambiguities. We propose to support the user with a machine learning technique that suggests keywords for articles in a literature collection browser. We provide visual explanations to make the keyword suggestions transparent. The suggestions are based on previous keyword assignments. The machine learning technique learns on the fly from the interactive assignments of the user. We seamlessly integrate the proposed technique in an existing literature collection browser and investigate various usage scenarios through an early prototype.
Beck, Fabian; Bergel, Alexandre; Bezemer, Cor-Paul; Isaacs, Katherine E.: Visualizing systems and software performance - Report on the GI-Dagstuhl seminar for young researchers, July 9-13, 2018. 2018. doi:10.7287/peerj.preprints.27253v1 Full text Citation Abstract Details
This GI-Dagstuhl seminar addressed the problem of visualizing performance-related data of systems and the software that they run. Due to the scale of performance-related data and the open-ended nature of analyzing it, visualization is often the only feasible way to comprehend, improve, and debug the performance behaviour of systems. The rise of cloud and big data systems, and the rapidly growing scale of the performance-related data that they generate, have led to an increased need for visualization of such data. However, the research communities behind data visualization, performance engineering, and high-performance computing are largely disjunct. The goal of this seminar was to bring together young researchers from these research areas to identify cross-community collaboration and to set the path for long-lasting collaborations towards rich and effective visualizations of performance-related data.
Sevastjanova, Rita; Beck, Fabian; Ell, Basil; Turkay, Cagatay; Henkin, Rafael; Butt, Miriam; Keim, Daniel; El-Assady, Mennatallah: Going beyond Visualization: Verbalization as Complementary Medium to Explain Machine Learning Models. In: Workshop on Visualization for AI Explainability at IEEE VIS. 2018. PDF Citation Abstract Details
In this position paper, we argue that a combination of visualization and verbalization techniques is beneficial for creating broad and versatile insights into the structure and decision-making processes of machine learning models. Explainability of machine learning models is emerging as an important area of research. Hence, insights into the inner workings of a trained model allow users and analysts, alike, to understand the models, develop justifications, and gain trust in the systems they inform. Explanations can be generated through different types of media, such as visualization and verbalization. Both are powerful tools that enable model interpretability. However, while their combination is arguably more powerful than each medium separately, they are currently applied and researched independently. To support our position that the combination of the two techniques is beneficial to explain machine learning models, we describe the design space of such a combination and discuss arising research questions, gaps, and opportunities.
Mumtaz, Haris; Beck, Fabian; Weiskopf, Daniel: Detecting Bad Smells in Software Systems with Linked Multivariate Visualizations. In: Proceedings of the 2018 IEEE Working Conference on Software Visualization. IEEE, 2018, p. 12-20. doi:10.1109/VISSOFT.2018.00010 PDF Citation Abstract Details
Parallel coordinates plots and RadViz are two visualization techniques that deal with multivariate data. They complement each other in identifying data patterns, clusters, and outliers. In this paper, we analyze multivariate software metrics linking the two approaches for detecting outliers, which could be the indicators for bad smells in software systems. Parallel coordinates plots provide an overview, whereas the RadViz representation allows for comparing a smaller subset of metrics in detail. We develop an interactive visual analytics system supporting automatic detection of bad smell patterns. In addition, we investigate the distinctive properties of outliers that are not considered harmful, but noteworthy for other reasons. We demonstrate our approach with open source Java systems and describe detected bad smells and other outlier patterns.
Frick, Veit; Grassauer, Thomas; Pinzger, Martin; Beck, Fabian: Generating Accurate and Compact Edit Scripts using Tree Differencing. In: Proceedings of the 2018 IEEE International Conference on Software Maintenance and Evolution. IEEE, 2018, p. 264-274. doi:10.1109/ICSME.2018.00036 PDF Citation Abstract Details
For analyzing changes in source code, edit scriptsare used to describe the differences between two versions of afile. These scripts consist of a list of actions that, applied to thesource file, result in the new version of the file. In contrast toline-based source code differencing, tree-based approaches suchas GumTree, MTDIFF, or ChangeDistiller extract changes bycomparing the abstract syntax trees (AST) of two versions of asource file. One benefit of tree-based approaches is their abilityto capture moved (sub) trees in the AST. Our approach, theIterative Java Matcher (IJM), builds upon GumTree and aims atgenerating more accurate and compact edit scripts that capturethe developer's intent. This is achieved by improving the qualityof the generated move and update actions, which are the mainsource of inaccurate actions generated by previous approaches. To evaluate our approach, we conducted a study with 11 external experts and manually analyzed the accuracy of 2400 randomly selected editactions. Comparing IJM to GumTree and MTDIFF, the resultsshow that IJM provides better accuracy for move and updateactions and is more beneficial to understanding the changes.
Herr, Dominik; Beck, Fabian; Ertl, Thomas: Visual Analytics for Decomposing Temporal Event Series of Production Lines. In: Proceedings of the 22nd International Conference on Information Visualisation. 2018. PDF Citation Abstract Details
The temporal analysis of events in a production line helps manufacturing experts get a better understanding of the line's performance and provides ideas for improvement. Especially the identification of recurring error patterns is important, because these patterns can be an indicator of systematic production issues. We present a visual analytics approach to analyze event reports of a production line. Reported events are shown as a time series plot that can be decomposed into a trend, seasonal, and remainder component by applying Seasonal Trend decomposition using Loess (STL). To find specific event patterns, the data is filtered based on aspects such as the event description or the processed product. Identified temporal patterns can be extracted from the original event series and compared visually with each other. In addition to predefined settings, experts can define a subseries of the event series and the period length of STL's seasonal component through an automatically optimized brushing of the undecomposed plot. We developed the approach together with an industry partner. To evaluate our approach, we conducted two pair analytics sessions with our industry partner's experts.
We demonstrate use cases from these sessions that showcase our approach's analytical potential. Moreover, we present general expert feedback that we collected through semi-structured interviews after the pair analytics sessions.
Latif, Shahid; Liu, Diao; Beck, Fabian: Exploring Interactive Linking Between Text and Visualization. In: EuroVis 2018 - Short Papers. 2018, p. 91-94. doi:10.2312/eurovisshort.20181084 PDF Citation Abstract Details
Visualizations are included in documents as augmentation to text and they become more intuitive if readers have the ability to interact with them. Modern web technologies facilitate the development of interactive documents including both text and visualizations. The aim of this research it to explore the design space of possible visualization–text linking and interactions based on various triggers such as mouse events. We describe a framework that takes text containing markup, a related dataset, and a configuration file as inputs and produces an interactive document. The resulting document provides interactions such as details on demand, visual highlighting and comparison, and bushing-and-linking. In addition to regular sized graphics, the use of word-sized graphics or sparklines presents related content in view-focus of the reader. Finally, an illustrative example is presented to showcase the approach.
Krüger, Robert; Simeonov, Georgi; Beck, Fabian; Ertl, Thomas: Visual Interactive Map Matching. In: IEEE Transactions on Visualization and Computer Graphics, Vol 24 (2018) No 6, p. 1881-1892. doi:10.1109/TVCG.2018.2816219 PDF Citation Abstract Details
Map matching is the process of assigning observed geographic positions of vehicles and their trajectories to the actual road links in a road network. In this paper, we present Visual Interactive Map Matching, a visual analytics approach to fine-tune the data preprocessing and matching process. It is based on ST-matching, a state-of-the-art and easy-to-understand map matching algorithm. Parameters of the preprocessing step and algorithm can be optimized with immediate visual feedback. Visualizations show current matching issues and performance metrics on a map and in diagrams. Manual and computer-supported editing of the road network model leads to a refined alignment of trajectories and roads. We demonstrate our approach with large-scale taxi trajectory data. We show that optimizing the matching on a subsample results in considerably improved matching quality, also when later scaled to the full dataset. An optimized matching ensures data faithfulness and prevents misinterpretation when the matched data might be investigated in follow-up analysis.
Karch, Grzegorz K.; Beck, Fabian; Ertl, Moritz; Meister, Christian; Schulte, Kathrin; Weigand, Bernhard; Ertl, Thomas; Sadlo, Filip: Visual Analysis of Inclusion Dynamics in Two-Phase Flow. In: IEEE Transactions on Visualization and Computer Graphics, Vol 24 (2018) No 5, p. 1841-1855. doi:10.1109/TVCG.2017.2692781 Citation Abstract Details
In single-phase flow visualization, research focuses on the analysis of vector field properties. In two-phase flow, in contrast, analysis of the phase components is typically of major interest. So far, visualization research of two-phase flow concentrated on proper interface reconstruction and the analysis thereof. In this paper, we present a novel visualization technique that enables the investigation of complex two-phase flow phenomena with respect to the physics of breakup and coalescence of inclusions. On the one hand, we adapt dimensionless quantities for a localized analysis of phase instability and breakup, and provide detailed inspection of breakup dynamics with emphasis on oscillation and its interplay with rotational motion. On the other hand, we present a parametric tightly linked space-time visualization approach for an effective interactive representation of the overall dynamics. We demonstrate the utility of our approach using several two-phase CFD datasets.
Sancho-Chavarria, Lilliana; Beck, Fabian; Weiskopf, Daniel; Mata-Montero, Erick: Task-based assessment of visualization tools for the comparison of biological taxonomies. In: Research Ideas and Outcomes, Vol 4 (2018) No e25742. doi:10.3897/rio.4.e25742 Full text Citation Abstract Details
Maintenance and curation of large-sized biological taxonomies are complex and laborious activities. Information visualization systems use interactive visual interfaces to facilitate analytical reasoning on complex information. Several approaches such as treemaps, indented lists, cone trees, radial trees, and many others have been used to visualize and analyze a single taxonomy. In addition, methods such as edge drawing, animation, and matrix representations have been used for comparing trees. Visualizing similarities and differences between two or more large taxonomies is harder than the visualization of a single taxonomy. On one hand, less space is available on the screen to display each tree; on the other hand, differences should be highlighted. The comparison of two alternative taxonomies and the analysis of a taxonomy as it evolves over time provide fundamental information to taxonomists and global initiatives that promote standardization and integration of taxonomic databases to better document biodiversity and support its conservation. In this work we assess how ten user visualization tasks for the curation of biological taxonomies are supported by several visualization tools. Tasks include the identification of conditions such as congruent taxa, splits, merges, and new species added to a taxonomy. We consider tools that have gone beyond the prototype stage, that have been described in peer-reviewed publications, or are in current use. We conclude with the identification of challenges for future development of taxonomy comparison tools.
Beck, Fabian; Siddiqui, Hafiz Ammar; Bergel, Alexandre; Weiskopf, Daniel: Method Execution Reports: Generating Text and Visualization to Describe Program Behavior. In: Proceedings of the 5th IEEE Working Conference on Software Visualization. IEEE, 2017, p. 1-10. doi:10.1109/VISSOFT.2017.14 PDF Citation Abstract Details
To obtain an accurate understanding of a program behavior, developers use a set of tools and techniques such as logging outputs, debuggers, profilers, and visualizations. These support an in-depth analysis of the program behavior, each approach focusing on a different aspect. What is missing, however, is an approach to get an overview of a program execution. As a first step to fill this gap, this paper presents an approach to generate Method Execution Reports. Each report summarizes the execution of a selected method for a specific execution of the program using natural-language text and embedded visualizations. A report provides an overview of the dynamic calls and time consumption related to the selected method. We present a framework to generate these reports and discuss the specific instantiation and phrasing we have chosen. Our results comprise feedback from developers discussing the understandability and usefulness of our approach and a task-based comparison to state-of-the-art solutions.
Brandt, Sebastian; Striewe, Michael; Beck, Fabian; Goedicke, Michael: A Dashboard for Visualizing Software Engineering Processes based on ESSENCE. In: Proceedings of the 5th IEEE Working Conference on Software Visualization. IEEE, 2017, p. 134-138. doi:10.1109/VISSOFT.2017.14 PDF Citation Abstract Details
While traditional project planning approaches focus on precise scheduling of tasks, the ESSENCE standard proposes a higher-level approach that focuses on monitoring. Hence, a new kind of process visualization that picks up ideas of Kanban boards and physical cards is sketched in the standard. This tool paper presents a dashboard application refining, extending, and implementing these ideas based on five use cases posed by two industry partners. It demonstrates that a high degree of support for project management can be achieved by using a relatively small set of visualization means.
Vehlow, Corinna; Beck, Fabian; Weiskopf, Daniel: Visualizing Group Structures in Graphs: a Survey. In: Computer Graphics Forum, Vol 36 (2017) No 6, p. 201-225. doi:10.1111/cgf.12872 PDF Citation Abstract Details
Graph visualizations encode relationships between objects. Abstracting the objects into group structures provides an overview of the data. Groups can be disjoint or overlapping, and might be organized hierarchically. However, the underlying graph still needs to be represented for analyzing the data in more depth. This work surveys research in visualizing group structures as part of graph diagrams. A particular focus is the explicit visual encoding of groups, rather than only using graph layout to indicate groups implicitly. We introduce a taxonomy of visualization techniques structuring the field into four main categories: visual node attributes vary properties of the node representation to encode the grouping, juxtaposed approaches use two separate visualizations, superimposed techniques work with two aligned visual layers, and embedded visualizations tightly integrate group and graph representation. The derived taxonomies for group structure and visualization types are also applied to group visualizations of edges. We survey group-only, group–node, group–link, and group–network tasks that are described in the literature as use cases of group visualizations. We discuss results from evaluations of existing visualization techniques as well as main areas of application. Finally, we report future challenges based on interviews we conducted with leading researchers of the field.
- Beck, Fabian; Bergel, Alexandre: Guest editorial of the special section on software visualization. In: Information and Software Technology, Vol 87 (2017), p. 221-222. doi:10.1016/j.infsof.2016.12.002 Citation Details
Beck, Fabian; Weiskopf, Daniel: Word-Sized Graphics for Scientific Texts. In: IEEE Transactions on Visualization and Computer Graphics, Vol 23 (2017) No 6, p. 1576-1587. doi:10.1109/TVCG.2017.2674958 PDF Citation Abstract Details
Generating visualizations at the size of a word creates dense information representations often called sparklines. The integration of word-sized graphics into text could avoid additional cognitive load caused by splitting the readers' attention between figures and text. In scientific publications, these graphics make statements easier to understand and verify because additional quantitative information is available where needed. In this work, we perform a literature review to find out how researchers have already applied such word-sized representations. Illustrating the versatility of the approach, we leverage these representations for reporting empirical and bibliographic data in three application examples. For interactive Web-based publications, we explore levels of interactivity and discuss interaction patterns to link visualization and text. We finally call the visualization community to be a pioneer in exploring new visualization-enriched and interactive publication formats.
Blascheck, Tanja; Schweizer, Markus; Beck, Fabian; Ertl, Thomas: Visual Comparison of Eye Movement Patterns. In: Computer Graphics Forum, Vol 36 (2017) No 3, p. 87-97. doi:10.1111/cgf.13170 PDF Citation Abstract Details
In eye tracking research, finding eye movement patterns and similar strategies between participants’ eye movements is important to understand task solving strategies and obstacles. In this application paper, we present a graph comparison method using radial graphs that show Areas of Interest (AOIs) and their transitions. An analyst investigates a single graph based on dwell times, directed transitions, and temporal AOI sequences. Two graphs can be compared directly and temporal changes may be analyzed. A list and matrix approach facilitate the analyst to contrast more than two graphs guided by visually encoded graph similarities. We evaluated our approach in case studies with three eye tracking and visualization experts. They identified temporal transition patterns of eye movements across participants, groups of participants, and outliers.
Beck, Fabian; Burch, Michael; Diehl, Stephan; Weiskopf, Daniel: A Taxonomy and Survey of Dynamic Graph Visualization. In: Computer Graphics Forum, Vol 36 (2017) No 1, p. 133-159. doi:10.1111/cgf.12791 PDF Citation Abstract Details
Dynamic graph visualization focuses on the challenge of representing the evolution of relationships between entities in readable, scalable, and effective diagrams. This work surveys the growing number of approaches in this discipline. We derive a hierarchical taxonomy of techniques by systematically categorizing and tagging publications. While static graph visualizations are often divided into node-link and matrix representations, we identify the representation of time as the major distinguishing feature for dynamic graph visualizations: either graphs are represented as animated diagrams or as static charts based on a timeline. Evaluations of animated approaches focus on dynamic stability for preserving the viewer’s mental map or, in general, compare animated diagrams to timeline-based ones. A bibliographic analysis provides insights into the organization and development of the field and its community. Finally, we identify and discuss challenges for future research. We also provide feedback from experts, collected with a questionnaire, which gives a broad perspective of these challenges and the current state of the field.
Beck, Fabian; Blascheck, Tanja; Ertl, Thomas; Weiskopf, Daniel: Word-Sized Eye Tracking Visualizations. In: Burch, Michael; Chuang, Lewis; Fisher, Brian; Schmidt, Albrecht; Weiskopf, Daniel (Ed.): Eye Tracking and Visualization. Springer, 2017, p. 113-128. PDF Citation Abstract Details
In user studies, eye tracking is often used in combination with other recordings, such as think-aloud protocols. However, it is difficult to analyze the eye tracking data and transcribed recordings together because of missing data alignment and integration. We suggest the use of word-sized eye tracking visualizations to augment the transcript with important events that occurred concurrently to the transcribed activities. We explore the design space of such graphics by discussing how existing eye tracking visualizations can be scaled down to word size. The suggested visualizations can optionally be combined with other event-based data such as interaction logs. We demonstrate our concept by a prototypical analysis tool.
Schulz, Christoph; Burch, Michael; Beck, Fabian; Weiskopf, Daniel: Visual Data Cleansing of Low-Level Eye Tracking Data. In: Burch, Michael; Chuang, Lewis; Fisher, Brian; Schmidt, Albrecht; Weiskopf, Daniel (Ed.): Eye Tracking and Visualization. Springer, 2017, p. 199-216. PDF Citation Abstract Details
Analysis and visualization of eye movement data from eye tracking studies typically take into account gazes, fixations, and saccades of both eyes filtered and fused into a combined eye. Although this is a valid strategy, we argue that it is also worth investigating low-level eye tracking data prior to high-level analysis, because today’s eye tracking systems measure and infer data from both eyes separately. In this work, we present an approach that supports visual analysis and cleansing of low-level time-varying data for eye tracking experiments. The visualization helps researchers get insights into the quality of the data in terms of its uncertainty, or reliability. We discuss uncertainty originating from eye tracking, and how to reveal it for visualization, using a comparative approach for disagreement between plots, and a density-based approach for accuracy in volume rendering. Finally, we illustrate the usefulness of our approach by applying it to eye movement data recorded with two state-of-the-art eye trackers.
Beck, Fabian; Acurana, Yasett; Blascheck, Tanja; Netzel, Rudolf; Weiskopf, Daniel: An Expert Evaluation of Word-Sized Visualizations for Analyzing Eye Movement Data. In: Proceedings of the 2016 IEEE Second Workshop on Eye Tracking and Visualization. 2016, p. 50-54. doi:10.1109/ETVIS.2016.7851166 PDF Citation Abstract Details
Word-sized visualizations for eye movement data allow analysts to compare a variety of experiment conditions or participants at the same time. We implemented a set of such word-sized visualizations as part of an analysis framework. We want to find out which of the visualizations is most suitable for different analysis tasks. To this end, we applied the framework to data from an eye tracking study on the reading behavior of users studying metro maps. In an expert evaluation with five analysts, we identified distinguishing characteristics of the different word-sized visualizations.
Blascheck, Tanja; Beck, Fabian; Baltes, Sebastian; Ertl, Thomas; Weiskopf, Daniel: Visual Analysis and Coding of Data-Rich User Behavior. In: Proceedings of the IEEE Conference on Visual Analytics Science & Technology 2016. IEEE, 2016, p. 141-150. doi:10.1109/VAST.2016.7883520 PDF Citation Abstract Details
Investigating user behavior involves abstracting low-level events to higher-level concepts. This requires an analyst to study individual user activities, assign codes which categorize behavior, and develop a consistent classification scheme. To better support this reasoning process of an analyst, we suggest a novel visual analytics approach which integrates rich user data including transcripts, videos, eye movement data, and interaction logs. Word-sized visualizations embedded into a tabular representation provide a space-efficient and detailed overview of user activities. An analyst assigns codes, grouped into code categories, as part of an interactive process. Filtering and searching helps to select specific activities and focus an analysis. A comparison visualization summarizes results of coding and reveals relationships between codes. Editing features support efficient assignment, refinement, and aggregation of codes. We demonstrate the practical applicability and usefulness of our approach in a case study and describe expert feedback.
Beck, Fabian; Burch, Michael; Weiskopf, Daniel: A Matrix-Based Visual Comparison of Time Series Sports Data. In: Vision, Modeling & Visualization. The Eurographics Association, 2016. doi:10.2312/vmv.20161342 PDF Citation Abstract Details
In sports, large amounts of data are measured and stored with the help of modern sensors and electronic devices. In particular, for endurance sports events, time-varying data are recorded and can be used to analyze the athletes' performance. Finding patterns and issues can help better understand results in sports competitions, which is of interest for the athletes, sports managers, and trainers alike. In this paper, we introduce a matrix-based approach to visually compare similar and dissimilar periods in performances of athletes. We differentiate the performances and visually encode these differences as color-coded matrix cells. The strengths of our approach are illustrated in a case study investigating the performances of two riders in the prologue of Tour de France 2012.
Schulz, Rodrigo; Beck, Fabian; Cerezo Felipez, Jhonny W.; Bergel, Alexandre: Visually Exploring Object Mutation. In: Proceedings of the 4th IEEE Working Conference on Software Visualization. IEEE, 2016. doi:10.1109/VISSOFT.2016.21 PDF Citation Abstract Details
Object-oriented programming supports object mutation during a program execution. A mutation occurs whenever a value is assigned to an object field. Analyzing the evolution of object mutation is known to be difficult. Unfortunately, classical code debuggers painfully support the analysis of object mutations. Object Evolution Blueprint is a visualization dedicated to exploring object mutation over time. Our blueprint visually and concisely represents sequences of field mutations. The history of each field is adequately shown with respect to the dynamic value types. We have observed the use of our blueprint with three practitioners. Our visualization has been well received and accepted to complete two different software comprehension tasks. Moreover, our user study shows that the visualization is both intuitive and simple to learn.
Vehlow, Corinna; Beck, Fabian; Weiskopf, Daniel: Visualizing Dynamic Hierarchies in Graph Sequences. In: IEEE Transactions on Visualization and Computer Graphics, Vol 22 (2016) No 10, p. 2343-2357. doi:10.1109/TVCG.2015.2507595 PDF Citation Abstract Details
Graphs are used to model relations between objects, where these objects can be grouped hierarchically based on their connectivity. In many applications, the relations change over time and so does the hierarchical group structure. We developed a visualization technique that supports the analysis of the topology and the hierarchical group structure of a dynamic graph and the tracking of changes over time. Each graph of a sequence is visualized by an adjacency matrix, where the hierarchical group structure is encoded within the matrix using indentation and nested contours, complemented by icicle plots attached to the matrices. The density within and between subgroups of the hierarchy is represented within the matrices using a gray scale. To visualize changes, transitions and dissimilarities between the hierarchically structured graphs are shown using a flow metaphor and color coding. The design of our visualization technique allows us to show more than one hierarchical group structure of the same graph by stacking the sequences, where hierarchy comparison is supported not only within but also between sequences. To improve the readability, we minimize the number of crossing curves within and between sequences based on a sorting algorithm that sweeps through the sequences of hierarchies.
Beck, Fabian; Melcher, Jan; Weiskopf, Daniel: Identifying Modularization Patterns by Visual Comparison of Multiple Hierarchies. In: Proceedings of the 2016 IEEE 24th International Conference on Program Comprehension. IEEE, 2016, p. 1-10. doi:10.1109/ICPC.2016.7503712 PDF Citation Abstract Details
Software is modularized to make its high complexity manageable. However, a multitude of modularization criteria exists and is applied. Hence, to extend, reuse, or restructure a system, it is important for developers to understand which criteria have been used. To this end, we provide an interactive visualization approach that compares the current modularization of a system to several software clustering results. The visualization is based on juxtaposed icicle plot representations of the hierarchical modularizations, encoding similarity by color. A detailed comparison is facilitated by an advanced selection concept. Coupling graphs, which form the basis for software clustering, can be explored on demand in matrix representations. We discuss typical modularization patterns that indicate criteria used for structuring the software or suggest opportunities for partial remodularization of the system. We apply the approach to analyze 16 open source Java projects. The results show that identifying those modularization patterns provides valuable insights and can be done efficiently.
Sancho-Chavarria, Lilliana; Beck, Fabian; Mata-Montero, Erick; Weiskopf, Daniel: Visual Comparison of Biological Taxonomies: A Task Characterization. In: Poster papers at EuroVis 2016. Eurographics, 2016. PDF Citation Abstract Details
Although biological taxonomies are a prevalent use case in hierarchy visualization, there has been little research on the characterization of users’ tasks for taxonomy comparison. Task identification is very relevant as a start point to design an effective information visualization solution for taxonomic work. We performed a systematic domain characterization that involved interviews with experts, literature review, the identification of data sources, and a survey of existing software tools. We performed iterative analysis until we reached a satisfactory list of users’ tasks. We present the tasks in a two-level model, describe them, and discuss future work.
Krüger, Robert; Sun, Guodao; Beck, Fabian; Liang, Ronghua; Ertl, Thomas: TravelDiff: Visual Comparison Analytics for Massive Movement Patterns Derived from Twitter. In: Proceedings of the IEEE Pacific Visualization Symposium. IEEE, 2016, p. 176-183. doi:10.1109/PACIFICVIS.2016.7465266 PDF Citation Abstract Details
Geo-tagged microblog data covers billions of movement patterns on a global and local scale. Understanding these patterns could guide urban and traffic planning or help coping with disaster situations. We present a visual analytics system to investigate travel trajectories of people reconstructed from microblog messages. To analyze seasonal changes and events and to validate movement patterns against other data sources, we contribute highly interactive visual comparison methods that normalize and contrast trajectories as well as density maps within a single view. We also compute an adaptive hierarchical graph from the trajectories to abstract individual movements into higher-level structures. Specific challenges that we tackle are, among others, the spatio-temporal sparsity of the data, the volume of data varying by region, and a diverse mix of means of transportation. The applicability of our approach is presented in three case studies.
Meyer, Matthias; Beck, Fabian; Lohmann, Steffen: Visual Monitoring of Process Runs: An Application Study for Stored Procedures. In: Proceedings of the IEEE Pacific Visualization Symposium. IEEE, 2016, p. 160-167. doi:10.1109/PACIFICVIS.2016.7465264 PDF Citation Abstract Details
Stored procedures are used in database systems to process and aggregate data. Hundreds of stored procedures often form a complex process network with documented and hidden dependencies that is difficult to understand, maintain, and debug. This paper introduces a novel approach to support such tasks by visually comparing a specific process run to other runs of the same process. The visualization is based on a force-directed node-link diagram arranged on a timeline. Color coding, histograms, and trend charts are used to highlight temporal deviations. The approach has been implemented as an interactive web application and used by professional database developers for solving realistic maintenance and debugging tasks. The feedback of these expert users confirms the usefulness and practical relevance of the approach.
Beck, Fabian; Koch, Sebastian; Weiskopf, Daniel: Visual Analysis and Dissemination of Scientific Literature Collections with SurVis. In: IEEE Transactions on Visualization and Computer Graphics, Vol 22 (2016) No 1, p. 180-189. doi:10.1109/TVCG.2015.2467757 PDF Citation Abstract Details
Bibliographic data such as collections of scientific articles and citation networks have been studied extensively in information visualization and visual analytics research. Powerful systems have been built to support various types of bibliographic analysis, but they require some training and cannot be used to disseminate the insights gained. In contrast, we focused on developing a more accessible visual analytics system, called SurVis, that is ready to disseminate a carefully surveyed literature collection. The authors of a survey may use our Web-based system to structure and analyze their literature database. Later, readers of the survey can obtain an overview, quickly retrieve specific publications, and reproduce or extend the original bibliographic analysis. Our system employs a set of selectors that enable users to filter and browse the literature collection as well as to control interactive visualizations. The versatile selector concept includes selectors for textual search, filtering by keywords and meta-information, selection and clustering of similar publications, and following citation links. Agreement to the selector is represented by word-sized sparkline visualizations seamlessly integrated into the user interface. Based on an analysis of the analytical reasoning process, we derived requirements for the system. We developed the system in a formative way involving other researchers writing literature surveys. A questionnaire study with 14 visual analytics experts confirms that SurVis meets the initially formulated requirements.
Beck, Fabian; Burch, Michael; Munz, Tanja; Di Silvestro, Lorenzo; Weiskopf, Daniel: Generalized Pythagoras Trees: A Fractal Approach to Hierarchy Visualization. In: Battiato, Sebastiano; Coquillart, Sabine; Pettré, Julien; Laramee, Robert S.; Kerren, Andreas; Braz, José (Ed.): Computer Vision, Imaging and Computer Graphics - Theory and Applications, VISIGRAPP 2014, Revised Selected Papers. Springer, 2016, p. 115-135. doi:10.1007/978-3-319-25117-2_8 PDF Citation Abstract Details
Through their recursive definition, many fractals have an inherent hierarchical structure. An example are binary branching Pythagoras Trees. By stopping the recursion in certain branches, a binary hierarchy can be encoded and visualized. But this binary encoding is an obstacle for representing general hierarchical data such as file systems or phylogenetic trees, which usually branch into more than two subhierarchies. We hence extend Pythagoras Trees to arbitrarily branching trees by adapting the geometry of the original fractal approach. Each vertex in the hierarchy is visualized as a rectangle sized according to a metric. We analyze several visual parameters such as length, width, order, and color of the nodes against the use of different metrics. Interactions help to zoom, browse, and filter the hierarchy. The usefulness of our technique is illustrated by two case studies visualizing directory structures and a large phylogenetic tree. We compare our approach with existing tree diagrams and discuss questions of geometry, perception, readability, and aesthetics.