GraphMaps: Browsing Large Graphs as Interactive Maps

Algorithms for laying out large graphs have seen significant progress in the past decade. However, browsing large graphs remains a challenge. Rendering thousands of graphical elements at once often results in a cluttered image, and navigating these elements naively can cause disorientation. To address this challenge we propose a method called GraphMaps, mimicking the browsing experience of online geographic maps. GraphMaps creates a sequence of layers, where each layer refines the previous one. During graph browsing, GraphMaps chooses the layer corresponding to the zoom level, and renders only those entities of the layer that intersect the current viewport. The result is that, regardless of the graph size, the number of entities rendered at each view does not exceed a predefined threshold, yet all graph elements can be explored by the standard zoom and pan operations. GraphMaps preprocesses a graph in such a way that during browsing, the geometry of the entities is stable, and the viewer is responsive. Our case studies indicate that GraphMaps is useful in gaining an overview of a large graph, and also in exploring a graph on a finer level of detail.Comment: submitted to GD 201

Code Park: A New 3D Code Visualization Tool

We introduce Code Park, a novel tool for visualizing codebases in a 3D game-like environment. Code Park aims to improve a programmer's understanding of an existing codebase in a manner that is both engaging and intuitive, appealing to novice users such as students. It achieves these goals by laying out the codebase in a 3D park-like environment. Each class in the codebase is represented as a 3D room-like structure. Constituent parts of the class (variable, member functions, etc.) are laid out on the walls, resembling a syntax-aware "wallpaper". The users can interact with the codebase using an overview, and a first-person viewer mode. We conducted two user studies to evaluate Code Park's usability and suitability for organizing an existing project. Our results indicate that Code Park is easy to get familiar with and significantly helps in code understanding compared to a traditional IDE. Further, the users unanimously believed that Code Park was a fun tool to work with.Comment: Accepted for publication in 2017 IEEE Working Conference on Software Visualization (VISSOFT 2017); Supplementary video: https://www.youtube.com/watch?v=LUiy1M9hUK

An energy-based model to optimize cluster visualization

National audienceGraphs are mathematical structures that provide natural means for complex-data representation. Graphs capture the structure and thus help modeling a wide range of complex real-life data in various domains. Moreover graphs are especially suitable for information visualization. Indeed the intuitive visualabstraction (dots and lines) they provide is intimately associated with graphs. Visualization paves the way to interactive exploratory data-analysis and to important goals such as identifying groups and subgroups among data and helping to understand how these groups interact with each other. In this paper, we present a graph drawing approach that helps to better appreciate the cluster structure in data and the interactions that may exist between clusters. In this work, we assume that the clusters are already extracted and focus rather on the visualization aspects. We propose an energy-based model for graph drawing that produces an esthetic drawing that ensures each cluster will occupy a separate zone within thevisualization layout. This method emphasizes the inter-groups interactions and still shows the inter-nodes interactions. The drawing areas assigned to the clusters can be user-specified (prefixed areas) or automatically crafted (free areas). The approach we suggest also enables handling geographically-based clustering. In the case of free areas, we illustrate the use of our drawing method through an example. In the case of prefixed areas, we firstuse an example from citation networks and then use another exampleto compare the results of our method to those of the divide and conquer approach. In the latter case, we show that while the two methods successfully point out the cluster structure our method better visualize the global structure

Preparing Software Re-Engineering via Freehand Sketches in Virtual Reality

Re-architecting a software system requires significant preparation, e.g., to scope and design new modules with their boundaries and constituent classes. When planning an intended future state of a system as a re-engineering goal, engineers often fall recur to mechanisms such as freehand sketching (using a whiteboard). While this ensures flexibility and expressiveness, the sketches remain disconnected from the source code. The alternative, tool-supported diagramming on the other hand considerably restricts flexibility and impedes free-form communication.We present a method for preparing the architectural software re-engineering via freehand sketches in virtual reality (VR) that can be seamlessly integrated with the model structure of a software visualization and, thus, also the code of a system, for productive use: Engineers explore a subject system in the immersive visualization, while freehand sketching their insights and plans. Our concept automatically interprets sketched shapes and connects them to the system’s source code, and superimposes code-level references into a sketch to support engineers in reflecting on their sketches.We evaluated our method in an iterative interview-based case study with software developers from four different companies, where they planned a hypothetical re-engineering of an opensource software system.Video Demonstration — https://youtu.be/NKC5YpH3n4

Visualization of large temporal social network datasets

Social network datasets consist of what sociologists call ‘social structures’, accumulation of all communication channels that social actors share ideas and information between each other. Social network analysis reveals characteristics and properties of social networks by applying specific metrics. Although, size of a real-life social network dataset can reach millions of relations belong to millions of social actors with large temporal dimension, existing information visualization tools can represent at most several thousands of these actors. This thesis presents a conceptual design study focused on visualization of large temporal social network datasets with a novel visualization method. Proposed technique combines Ideal Gas Law (IGL) with Jacob Moreno’s theory of The Cannon of Creativity to layout social network datasets in 3D hyperbolic space and can render 50,000 social actors at interactive speed. A proof-of-the-concept program is developed around this technique allowing users to perform several analysis tasks on temporal social network datasets. Users can explore the network, control the amount of visual clutter, and identify communication anomalies in run time. Moreover, they can search a specific actor and visually follow her communication pattern. The effectiveness of proposed technique is presented with case and usability studies performed using generated and real-life datasets. In particular the Enron email dataset (323,073 emails, 19,898 email addresses over four years) and 20 Newsgroups (44,797 postings, 20 news groups and 5417 email addresses over one month) datasets are analyzed

Visualization of the Static aspects of Software: a survey

International audienceSoftware is usually complex and always intangible. In practice, the development and maintenance processes are time-consuming activities mainly because software complexity is difficult to manage. Graphical visualization of software has the potential to result in a better and faster understanding of its design and functionality, saving time and providing valuable information to improve its quality. However, visualizing software is not an easy task because of the huge amount of information comprised in the software. Furthermore, the information content increases significantly once the time dimension to visualize the evolution of the software is taken into account. Human perception of information and cognitive factors must thus be taken into account to improve the understandability of the visualization. In this paper, we survey visualization techniques, both 2D- and 3D-based, representing the static aspects of the software and its evolution. We categorize these techniques according to the issues they focus on, in order to help compare them and identify the most relevant techniques and tools for a given problem

Εργαλείο Οπτικοποίησης για την Υποστήριξη της Εξερεύνησης Δημόσιων Υπηρεσιών σε Πληροφοριακά Συστήματα Ηλεκτρονικής Διακυβέρνησης

Διπλωματική εργασία--Πανεπιστήμιο Μακεδονίας, Θεσσαλονίκη, 2010.Πολλές φορές ο τρόπος που παρουσιάζονται οι πληροφορίες στα κυβερνητικά portals και τα εργαλεία που παρέχονται στους χρήστες για να τις εξερευνήσουν, έχουν σαν αποτέλεσμα το χαμηλό βαθμό χρηστικότητας των portals και επομένως την πλημμελή πρόσβαση στις ίδιες τις πληροφορίες. Τις περισσότερες φορές αυτές οι πληροφορίες αφορούν σε Δημόσιες Υπηρεσίες (ΔΥ) και στην πολύπλοκη δομή τους. Στόχος αυτής της εργασίας είναι η ανάπτυξη και παρουσίαση ενός νέου εργαλείου οπτικοποίησης δημόσιων υπηρεσιών και των μεταξύ τους σχέσεων. Το εργαλείο αυτό σχεδιάστηκε και υλοποιήθηκε για να διερευνηθεί ένας νέος τρόπος παρουσίασης, μέσω οπτικοποίησης, σχεσιακών δεδομένων, όπως είναι το σύνολο των δημόσιων υπηρεσιών ενός κράτους και πώς αυτός ο τρόπος παρουσίασης μπορεί να συμβάλει, έναντι άλλων τρόπων, στην βελτίωση της εμπειρίας του χρήστη κατά την αναζήτηση υπηρεσιών και την περιήγηση του στους δαιδαλώδεις διαδρόμους τους. Η υλοποίηση του προαναφερθέντος εργαλείου στηρίχθηκε στην χρήση δομημένου τρόπου περιγραφής των δημοσίων υπηρεσιών μέσω του Governance Enterprise Architecture Service Model (GEA)[24] [25] για το οποίο θα γίνει σύντομη περιγραφή στο κεφάλαιο 2. Η τυποποίηση του τρόπου περιγραφής των δημόσιων υπηρεσιών επιδιώκει να αντιμετωπίσει το θέμα της ύπαρξης κατακερματισμού και ασυνέπειας στην περιγραφή των υπηρεσιών τόσο στη Δημόσια Διοίκηση του ίδιου κράτους όσο και μεταξύ διαφορετικών κρατών. Η μη ύπαρξη τυποποιημένης περιγραφής καθιστά δυσχερή και τις περισσότερες φορές αδύνατη: Την κατανόηση και χρήση των δημόσιων υπηρεσιών από τον πολίτη-χρήστη του υπολογιστικού συστήματος. Την κατανόηση και επεξεργασία των δημόσιων υπηρεσιών από αυτόν που πρέπει να προσφέρει την υπηρεσία μέσω υπολογιστικών συστημάτων, δηλ. τον δημόσιο φορέα. Τη συνεννόηση και συνεργασία των διαφορετικών υπολογιστικών συστημάτων μέσα στην ίδια Δημόσια Διοίκηση. Τη συνεννόηση και συνεργασία των διαφορετικών υπολογιστικών συστημάτων μεταξύ των Δημόσιων Διοικήσεων διαφορετικών κρατών. Η λύση των ανωτέρω προβλημάτων θα κάνει τη Δημόσια Διοίκηση πολύ πιο αποτελεσματική και αποδοτική τόσο στη σχέση της με τους πολίτες αλλά και στον «εσωτερικό της κόσμο», δηλ. στην αλληλεπίδραση και συνεργασία μεταξύ των φορέων της. Σ’ αυτή την κατεύθυνση επιχειρεί να παρέχει υποστήριξη το νέο εργαλείο οπτικοποίησης συμβάλλοντας στη βελτίωση της εμπειρίας των χρηστών όταν εισέρχονται σ’ ένα portal ηλεκτρονικής διακυβέρνησης (e-government) για να αναζητήσουν δημόσιες υπηρεσίες που είναι κατάλληλες γι’ αυτούς. Το εργαλείο οπτικοποίησης παρέχει ένα νέο τρόπο παρουσίασης των υπηρεσιών αυτών, κάνοντας χρήση, κατά κύριο λόγο, γραφικών, εικόνων, κίνησης (animation) και αλληλεπίδρασης (interaction) με το οπτικό του περιβάλλον. Στο κεφάλαιο 3 παρουσιάζονται κάποια από τα γνωστότερα και πιο συναφή έργα και τεχνολογίες σχετικά με την υποστήριξη της παροχής υπηρεσιών στο Δημόσιο Τομέα. Στο κεφάλαιο 4 παρουσιάζεται το λογισμικό ανοικτού κώδικα Birdeye RaVis στο οποίο βασίστηκε η ανάπτυξη του «Εργαλείου Οπτικοποίησης ΔΥ» και στη συνέχεια το ίδιο το «Εργαλείο Οπτικοποίησης ΔΥ», οι τροποποιήσεις του RaVis που έγιναν ώστε να γίνει δυνατή η βελτίωση του και οι λειτουργίες του νέου «Εργαλείου Οπτικοποίησης ΔΥ». Στο πέμπτο κεφάλαιο παρουσιάζεται ένα παράδειγμα εφαρμογής με πραγματικά δεδομένα, στο οποίο χρησιμοποιήθηκαν τέσσερις Δημόσιες Υπηρεσίες (ΔΥ), κατά το μοντέλο GEA, έτσι όπως καταγράφηκαν στο πλαίσιο ενός έργου eGovernment του Εργαστήριου Πληροφοριακών Συστημάτων του Πανεπιστημίου Μακεδονία. Τέλος, στο έκτο κεφάλαιο συνάγονται τα συμπεράσματα αυτής της εργασίας και καταγράφονται οι προτάσεις για μελλοντική δουλειά προς την κατεύθυνση της βελτίωσης της οπτικοποίησης των ΔΥ

Identifying Changes of Functional Brain Networks using Graph Theory

This thesis gives an overview on how to estimate changes in functional brain networks using graph theoretical measures. It explains the assessment and definition of functional brain networks derived from fMRI data. More explicitly, this thesis provides examples and newly developed methods on the measurement and visualization of changes due to pathology, external electrical stimulation or ongoing internal thought processes. These changes can occur on long as well as on short time scales and might be a key to understanding brain pathologies and their development. Furthermore, this thesis describes new methods to investigate and visualize these changes on both time scales and provides a more complete picture of the brain as a dynamic and constantly changing network.:1 Introduction 1.1 General Introduction 1.2 Functional Magnetic Resonance Imaging 1.3 Resting-state fMRI 1.4 Brain Networks and Graph Theory 1.5 White-Matter Lesions and Small Vessel Disease 1.6 Transcranial Direct Current Stimulation 1.7 Dynamic Functional Connectivity 2 Publications 2.1 Resting developments: a review of fMRI post-processing methodologies for spontaneous brain activity 2.2 Early small vessel disease affects fronto-parietal and cerebellar hubs in close correlation with clinical symptoms - A resting-state fMRI study 2.3 Dynamic modulation of intrinsic functional connectivity by transcranial direct current stimulation 2.4 Three-dimensional mean-shift edge bundling for the visualization of functional connectivity in the brain 2.5 Dynamic network participation of functional connectivity hubs assessed by resting-state fMRI 3 Summary 4 Bibliography 5. Appendix 5.1 Erklärung über die eigenständige Abfassung der Arbeit 5.2 Curriculum vitae 5.3 Publications 5.4 Acknowledgement

visone - Software for the Analysis and Visualization of Social Networks

We present the software tool visone which combines graph-theoretic methods for the analysis of social networks with tailored means of visualization. Our main contribution is the design of novel graph-layout algorithms which accurately reflect computed analyses results in well-arranged drawings of the networks under consideration. Besides this, we give a detailed description of the design of the software tool and the provided analysis methods