HCI Bibliography Home | HCI Journals | About VLC | Journal Info | VLC Journal Volumes | Detailed Records | RefWorks | EndNote | Hide Abstracts
VLC Tables of Contents: 16171819202122232425

Journal of Visual Languages & Computing 24

Editors:S.-K. Chang; Stefano Levialdi
Standard No:ISSN: 1045-926X
Links:Table of Contents
  1. VLC 2013-02 Volume 24 Issue 1
  2. VLC 2013-04 Volume 24 Issue 2
  3. VLC 2013-06 Volume 24 Issue 3
  4. VLC 2013-08 Volume 24 Issue 4
  5. VLC 2013-10 Volume 24 Issue 5
  6. VLC 2013-12 Volume 24 Issue 6

VLC 2013-02 Volume 24 Issue 1

Biometric system adaptation by self-update and graph-based techniques BIBAKFull-Text 1-9
  Ajita Rattani; Gian Luca Marcialis; Fabio Roli
Self-update is the most commonly adopted biometric template update technique in which the system adapts itself to the confidently classified samples. However, the recent works indicate that self-update has limited capability to capture samples representing significant intra-class variations. As an alternative, a biometric template update technique based on the graph-based representation is proposed. This technique can potentially capture samples with significant variations, resulting in efficient adaptation. Until now, the efficacy of these adaptation techniques has been proven only on the basis of experimental evaluations on small data sets. The contribution of this paper lies in (a) conceptual explanation of the functioning of self-update and graph-based techniques to template adaptation leading to efficacy of the latter and (b) evaluation of the performance of these adaptation techniques in comparison to the baseline system without adaptation. Experiments are conducted on the large DIEE data set, explicitly collected for this aim. Reported results validate the superiority of the graph-based technique over self-update.
Keywords: Biometric template updating; Graph min-cut; Self-update; Semi-supervised learning
Modeling collaboration protocols for collaborative modeling tools: Experiences and applications BIBAKFull-Text 10-23
  Jesús Gallardo; Crescencio Bravo; Miguel A. Redondo; Juan de Lara
Over the last two decades, Collaborative Systems have become increasingly popular thanks to the many advances made in networks, communications and software tools. Within this field, Collaborative Modeling Systems apply the collaborative paradigm to the construction of (often visual) models, where users build diagrams from building blocks and the relationships between them. In these kinds of applications, the work is usually arranged into sessions, with the definition of some kind of time organization between those sessions. This organization is known as a collaboration protocol. Unfortunately, it is not usually easy to define these protocols, and many applications do not allow users to make any use of them.
   In an effort to overcome these difficulties, in this paper we propose a visual language for defining collaboration protocols for these systems. As such, in our language, sessions, artifacts and the transformations between them can be specified visually, and different coordination relationships (such as fork and join) can be defined. The visual language is included in a development method for collaborative systems that take advantage of the Eclipse platform in order to develop model-driven graphical editors that are enhanced with collaboration capabilities.
Keywords: Collaboration protocols; Visual languages; Model-driven software development; Groupware
Time Automaton: A visual mechanism for temporal querying BIBAKFull-Text 24-36
  Luís Certo; Teresa Galvão; José Borges
Available visual temporal querying tools do not provide the means for formulating complex temporal queries. For these queries users have to adopt text-based querying languages, such as SQL. The problem, however, is that using text-based languages is less comfortable than using visual tools and, most important, in some cases temporal queries can be extremely difficult to formulate for users that do not possess programming competences. In this paper we propose the Time Automaton, a highly flexible visual mechanism that enables the formulation of a large set of different types of temporal queries, ranging from the simple to the most complex ones. To prove its practical application we created a tool that implements the mechanism and used it to analyze a real dataset. Time Automaton was validated against a representative sample of temporal queries extracted from the matured OWL-Time Ontology. In order to understand if users, with or without programming competences, could understand and use the Time Automaton we conducted a usability experiment.
Keywords: Visual mechanism; Temporal querying; Finite state automata
Interactive customization of ubiquitous Web applications BIBAKFull-Text 37-52
  G. Ghiani; F. Paternò; C. Santoro
Ubiquitous environments pose new challenges for end users who often need to access their applications from various devices. In this paper we present a solution that allows users to easily customise and migrate interactive web applications starting with an existing desktop version. This is obtained through an intelligent infrastructure that enables users to select the relevant part of an interactive Web application in order to create a mobile version and migrate it.
Keywords: Ubiquitous Web user interfaces; End user customization; Migratory interfaces
A kernel-based framework for image collection exploration BIBAKFull-Text 53-67
  Jorge E. Camargo; Juan C. Caicedo; Fabio A. Gonzalez
While search engines have been a successful tool to search text information, image search systems still face challenges. The keyword-based query paradigm used to search in image collection systems, which has been successful in text retrieval, may not be useful in scenarios where the user does not have the precise way to express a visual query. Image collection exploration is a new paradigm where users interact with the image collection to discover useful and relevant pictures. This paper proposes a framework for the construction of an image collection exploration system based on kernel methods, which offers a mathematically strong basis to address each stage of an image collection exploration system: image representation, summarization, visualization and interaction. In particular, our approach emphasizes a semantic representation of images using kernel functions, which can be seamlessly harnessed across all system components. Experiments were conducted with real users to verify the effectiveness and efficiency of the proposed strategy.
Keywords: Image collection exploration; Exploratory search; Summarization; Visualization; Kernel methods

VLC 2013-04 Volume 24 Issue 2

A general theory of spatial relations to support a graphical tool for visual information extraction BIBAKFull-Text 71-87
  Giuseppe Della Penna; Daniele Magazzeni; Sergio Orefice
In this paper we present a general spatial composition framework which allows one to model the graphical objects and the spatial relations of a large class of visual languages. The new formalism has been implemented within the SRQ tool, a software system for the Visual Information Extraction, enabling it to work on a wider range of domains. In particular, in the paper we describe the application of SRQ to geospatial data.
Keywords: Information extraction; Visual information search; Spatial relations; Geospatial data analysis
A visual language for explaining probabilistic reasoning BIBAKFull-Text 88-109
  Martin Erwig; Eric Walkingshaw
We present an explanation-oriented, domain-specific, visual language for explaining probabilistic reasoning. Explanation-oriented programming is a new paradigm that shifts the focus of programming from the computation of results to explanations of how those results were computed. Programs in this language therefore describe explanations of probabilistic reasoning problems. The language relies on a story-telling metaphor of explanation, where the reader is guided through a series of well-understood steps from some initial state to the final result. Programs can also be manipulated according to a set of laws to automatically generate equivalent explanations from one explanation instance. This increases the explanatory value of the language by allowing readers to cheaply derive alternative explanations if they do not understand the first. The language is composed of two parts: a formal textual notation for specifying explanation-producing programs and the more elaborate visual notation for presenting those explanations. We formally define the abstract syntax of explanations and define the semantics of the textual notation in terms of the explanations that are produced.
Keywords: Explanation; Probability; Story telling; Explanation transformation; Language semantics
A visual programming language for XML manipulation BIBAKFull-Text 110-135
  Gilbert Tekli; Richard Chbeir; Jacques Fayolle
XML data flow has reached beyond the world of computer science and has spread to other areas such as data communication, e-commerce and instant messaging. Therefore, manipulating this data by non-expert programmers is becoming imperative and has emerged two alternatives. On one hand, Mashups have emerged a few years ago, providing users with visual tools for web data manipulation but not necessarily XML specific. Mashups have been leaning towards functional composition but no formal definitions have yet been defined. On the other hand, visual languages for XML have been emerging since the standardization of XML, and mostly relying on querying XML data for extraction or structure transformations. These languages are mainly based on existing textual XML languages, they have limited expressiveness and do not provide non-expert programmers with means to manipulate XML data. In this paper, we define a generic visual language called XCDL based on Colored Petri Nets allowing non-expert programmers to compose manipulation operations. The XML manipulations range from simple data selection/projection to data modification (insertion, removal, obfuscation, etc.). The language is oriented to deal with XML data (XML documents and fragments), providing users with means to compose XML oriented operations. The language core syntax is presented here along with an implemented prototype based on it.
Keywords: Visual languages; Language syntax and specification; Colored Petri Nets; Composition; XML data manipulation; Concurrency
Scenario-driven analysis of systems specified through graph transformations BIBAKFull-Text 136-145
  Vahid Rafe
Model checking is one of the most accurate analysis techniques which are used to verify software and hardware systems. However, the analysis of large and complex systems tends to become infeasible since their state spaces easily become too big. Besides well-known abstraction techniques, which may hamper the accuracy of results, in this paper we propose the use of scenario-driven model checking to address and mitigate the state explosion problem. The proposal starts from systems specified through a Graph Transformation (GT) system and it is focused on the analysis of the most significant scenarios. We exploit the modularity of GT systems to reduce the state space by eliminating all the nodes and rules that are not involved in the scenario. Focused analysis also helps concentrate on the most critical behaviors of the system and smooth the risks associated with them. The paper introduces the analysis approach and explains how scenarios (specified in terms of sequence diagrams) can help to reduce the state space. All main concepts are illustrated through a simple application for a travel agency specified as if it were a service-oriented application.
Keywords: Graph transformation; Scenario-driven model checking; State space reduction


Visualization in management: From communication to collaboration. A response to Zhang BIBAKFull-Text 146-149
  Martin J. Eppler; Sabrina Bresciani
The benefits of visualization are starting to be exploited in the field of management. Beyond cognitive and communicative advantages, this view point article highlights how visualization can enhance collaborative activities in organizations. Recent trends in management indicate that the activity of visualizing can be as important as the pictures that are generated. Qualitative visualizations such as conceptual diagrams, metaphors or sketches are used as collaboration catalysts to facilitate a variety of tasks, from idea generation to decision making and planning. The article derives future research avenues in this promising and interdisciplinary field of inquiry, including the impact of immersive worlds, electronic sketches or multi-user interfaces for collaborative managerial tasks.
Keywords: Visual communication; Visualization; Management; Collaboration

VLC 2013-06 Volume 24 Issue 3

Graph Transformation and Visual Modeling Techniques

Preface BIBFull-Text 151-152
  Fabio Gadducci; Leonardo Mariani
Compositional and behavior-preserving reconfiguration of component connectors in Reo BIBAKFull-Text 153-168
  Christian Krause; Holger Giese; Erik de Vink
It is generally accepted that building software out of loosely coupled components, such as in service-oriented systems or mobile networks, yields applications that are more robust against changes and failure of single components than monolithic systems. In order to accommodate for changes in the environment or in the requirements, and anticipate to a component failure, applications are often dynamically adapted by means of a reconfiguration. In this paper, we target the visual channel-based coordination language Reo and introduce a combined structural and behavioral model for graph-based component connectors in Reo. Exploiting concepts from category theory, we model reconfigurations of connectors as transformations of the underlying connector graphs. We show that our connector model has a compositional semantics and lift structural reconfigurations to the semantical level. As a concrete application of our framework, we introduce a notion of behavior-preserving reconfiguration for Reo and provide a sufficient condition to ensure behavior-preservation statically.
Keywords: Coordination languages; Reconfiguration; Behavior-preservation; Semantics; Category theory
Extending Spider Diagrams for policy definition BIBAKFull-Text 169-191
  P. Bottoni; A. Fish
Spider Diagrams (SDs) are a well-established visual language used to specify sets, their relationships, and constraints on their cardinalities. We propose two extensions allowing their use in the definition of temporal policies. Firstly, Timed SDs (TSDs) enable the expression of temporal constraints. We adopt an interval-based model of calendar time, permitting diagram elements to be specified to exist only over some interval. We introduce basic TSDs, where time constraints refer to an entire diagram rather than individual elements, as a canonical form for TSDs, and decompose complex TSDs into comic strip-like sequences of basic TSDs. Secondly, we introduce an innovative usage of SDs by specialising and adapting them to an OO-modelling context: in type-SDs a spider represents a type, whereas in instance-SDs a spider represents a specific object of a given type. A notion of conformance of an instance-SD to a type-SD ensues and we extend the concepts to instance-TSDs and type-TSDs. Finally, we combine extensions to allow the specification of temporal policies, which define permissible states for instances of some given type over a period without temporal gaps in it, and introduce a notion of conformance to a policy for a sequence of time-annotated instances.
Keywords: Visual logic; Temporal constraint specification; Spider Diagrams; Policy; Visual modelling
Treewidth, pathwidth and cospan decompositions with applications to graph-accepting tree automata BIBAKFull-Text 192-206
  Christoph Blume; H. J. Sander Bruggink; Martin Friedrich; Barbara König
We will revisit the categorical notion of cospan decompositions of graphs and compare it to the well-known notions of path decomposition and tree decomposition from graph theory. More specifically, we will define several types of cospan decompositions with appropriate width measures and show that these width measures coincide with pathwidth and treewidth. Such graph decompositions of small width are used to efficiently decide graph properties, for instance via graph automata. Hence we will give an application by defining graph-accepting tree automata, thus integrating previous work by Courcelle into the setting of cospan decompositions. Furthermore we will show that regardless of whether we consider path or tree decompositions, we arrive at the same notion of recognizability.
Keywords: Cospans; Graph decompositions; Pathwidth; Treewidth; Tree automata
Graph transformations and software engineering: Success stories and lost chances BIBAKFull-Text 207-217
  Giovanni Toffetti; Mauro Pezzè
Textual as well as visual and diagrammatic notations are essential in software engineering, and are used in many different contexts. Chomsky grammars are the key tool to handle textual notations, and find many applications for textual languages. Visual and diagrammatic languages add spatial dimensions that reduce the applicability of textual grammars and call for new tools.
   Graph transformation systems have been studied for over 40 years and are a powerful tool to deal with syntax, semantics and transformation of diagrammatic notations. The enormous importance of visual and diagrammatic languages and the strong support that graph transformation provide to the manipulation of diagrammatic notations would suggest a big success of graph transformation in software engineering.
   Graph transformation systems find their application both as language generating devices and specification means for system evolution, and thus can have many applications in software engineering. In this paper we discuss the main features of graph transformation and how they can help software engineers. We look back to the many attempts to use graph transformations in software engineering in the last 15 years, identify some success stories, and discuss to what extent graph transformation succeeded, when they have not succeeded yet, what are the main causes of failures, and how they can help software engineering in the next 15 years.
Keywords: Graph transformation; Software engineering; Model; Model transformation; Visual language; Dynamic system; Evolving system
Semiotic perspectives on interactive languages for life on the screen BIBAKFull-Text 218-221
  Clarisse Sieckenius de Souza
Cross-disciplinary research involving semiotics and computer science is rare. With the Web 2.0, contemporary activities of users can be properly described as real 'life on the screen'. One of the challenges for the design of interactive languages is to support these activities and to express the much wider variety of meanings that users want to exchange through and with software. As the discipline whose aim is to investigate meanings, through representation and interpretation processes, semiotics is remarkably well-positioned to contribute with new knowledge in our field. This viewpoint article examines the reasons why in spite of this positioning, semiotics remains unpopular among researchers interested in interactive computer languages. In particular, it proposes that a semiotic approach can help us think about computer languages to represent our individual and collective 'selves' on the screen.
Keywords: Computer semiotics; Interactive languages; Computer languages; Virtual self-representation

VLC 2013-08 Volume 24 Issue 4

Visualization experience and related process modeling BIBAKFull-Text 223-233
  Ilya Malyanov; Brian J. d'Auriol; Sungyoung Lee
The visualization process is a transformation of information content into knowledge via a visual representation. Visualization experience, proposed herein, reflects human sensations arising during the visualization process. It provides a basis in which to objectively measure and evaluate human participation in the visualization process; and thereby provides methods of control. Visualization experience modeling allows leveraging on the natural environment to augment understanding, therefore improve decision making. The application emphasis in this paper is on the theoretical development of visualization experience in the visualization process as applied to Ambient Assisted Living and Clinical Decision Support Systems.
Keywords: Visualization; Visualization experience; CDSS; Ambient assisted living
Interpretation of strokes in radial menus: The case of the KeyScretch text entry method BIBAKFull-Text 234-247
  Gennaro Costagliola; Vittorio Fuccella; Michele Di Capua
Most of the recently proposed text entry methods for touch screen devices are stroke-based: the traditional tapping interaction is being replaced with a more natural gesture, performed through a pointer (pen or finger) on a soft keyboard. These methods need an effective technique to interpret user strokes, in order to correctly obtain the text the user intends to enter. KeyScretch is a recent text entry method based on menu-augmented soft keyboards. The method introduces a new way of interacting with radial menus through compound strokes. In this paper we present the technology used for recognizing these strokes. In particular, the design of different recognizers is presented and their performances are compared. The evaluation shows that geometric stroke recognition techniques, associated to other calibrations, can significantly improve the accuracy achievable using a simple target-based method.
Keywords: KeyScretch; Text entry; Menu; Soft keyboard; Stroke recognition
Cognitive artifacts as a window on design BIBAKFull-Text 248-261
  John M. Carroll; Marcela Borge; Shin-I Shih
We are investigating information analysis as a kind of problem solving in which teams are presented with a collection of facts regarding people, places and events, and then identify underlying connections, patterns, and plans in order to draw specific conclusions. The teams spontaneously created a variety of artifacts to hold and organize problem information, and practices to simplify and regularize their collaborative interactions around these artifacts. In this paper, we analyze the artifacts and practices as a potential source of insight into how this problem solving activity could be supported by an interactive system design.
Keywords: Information analysis; Information artifacts; Design of interactive systems
Improving multiple aesthetics produces better graph drawings BIBAKFull-Text 262-272
  Weidong Huang; Peter Eades; Seok-Hee Hong; Chun-Cheng Lin
Many automatic graph drawing algorithms implement only one or two aesthetic criteria since most aesthetics conflict with each other. Empirical research has shown that although those algorithms are based on different aesthetics, drawings produced by them have comparable effectiveness.
   The comparable effectiveness raises a question about the necessity of choosing one algorithm against another for drawing graphs when human performance is a main concern. In this paper, we argue that effectiveness can be improved when algorithms are designed by making compromises between aesthetics, rather than trying to satisfy one or two of them to the fullest. We therefore introduce a new algorithm: BIGANGLE. This algorithm produces drawings with multiple aesthetics being improved at the same time, compared to a classical spring algorithm. A user study comparing these two algorithms indicates that BIGANGLE induces a significantly better task performance and a lower cognitive load, therefore resulting in better graph drawings in terms of human cognitive efficiency.
   Our study indicates that aesthetics should not be considered separately. Improving multiple aesthetics at the same time, even to small extents, will have a better chance to make resultant drawings more effective. Although this finding is based on a study of algorithms, it also applies in general graph visualization and evaluation.
Keywords: Graph drawing; Force-directed algorithms; Aesthetic criteria; Crossing angles; Angular resolution; Evaluation; Effectiveness
On the expressiveness of spider diagrams and commutative star-free regular languages BIBAKFull-Text 273-288
  Aidan Delaney; Gem Stapleton; John Taylor; Simon Thompson
Spider diagrams provide a visual logic to express relations between sets and their elements, extending the expressiveness of Venn diagrams. Sound and complete inference systems for spider diagrams have been developed and it is known that they are equivalent in expressive power to monadic first-order logic with equality, MFOL[=]. In this paper, we further characterize their expressiveness by articulating a link between them and formal languages. First, we establish that spider diagrams define precisely the languages that are finite unions of languages of the form KUUΓ*, where K is a finite commutative language and Γ is a finite set of letters. We note that it was previously established that spider diagrams define commutative star-free languages. As a corollary, all languages of the form KUUΓ* are commutative star-free languages. We further demonstrate that every commutative star-free language is also such a finite union. In summary, we establish that spider diagrams define precisely: (a) languages definable in MFOL[=], (b) the commutative star-free regular languages, and (c) finite unions of the form KUUΓ*, as just described.
Keywords: Spider diagrams; Diagrammatic logics; Regular languages; Expressiveness; Star-free languages
Exploring hierarchical multidimensional data with unified views of distribution and correlation BIBAKFull-Text 289-312
  Mark John Sifer; John Michael Potter
Data analysts explore data by inspecting features such as clustering, distribution and correlation. Much existing research has focused on different visualisations for different data exploration tasks. For example, a data analyst might inspect clustering and correlation with scatterplots, but use histograms to inspect a distribution. Such visualisations allow an analyst to confirm prior expectations. For example, a scatterplot may confirm an expected correlation or may show deviations from the expected correlation. In order to better facilitate discovery of unexpected features in data, however, a combination of different perspectives may be needed. In this paper, we combine distributional and correlational views of hierarchical multidimensional data. Our unified view supports the simultaneous exploration of data distribution and correlation. By presenting a unified view, we aim to increase the chances of discovery of unexpected data features, and to provide the means to explore such features in detail. Further, our unified view is equipped with a small number of primitive interaction operators which a user composes to facilitate smooth and flexible exploration.
Keywords: Data analysis; Multidimensional data; Data distribution; Correlation

VLC 2013-10 Volume 24 Issue 5

Assisting comprehension of animation programs through interactive code visualization BIBAKFull-Text 313-326
  Yan Zhang; Sheela Surisetty; Christopher Scaffidi
Visual languages have been widely used to help people create animation programs. However, current programming environments lack features supporting efficient code exploration and program comprehension, particularly for understanding relationships among parts of animation programs. In this paper, we present novel interactive visualizations aimed at helping people to understand animation programs. We conducted an empirical study to evaluate the impact of these visualizations on programmer comprehension of the code, showing that our approach enabled programmers to comprehend more information with less effort and in less time. This result is potentially significant because it demonstrates an approach for helping users to explore and understand animation code. We anticipate that this approach could be applied in a wide variety of animation programming tools, which could ease common animation programming tasks that require understanding code.
Keywords: Animation programming; Visualization; Novice programmers
On the expressiveness of second-order spider diagrams BIBAKFull-Text 327-349
  Peter Chapman; Gem Stapleton; Aidan Delaney
Existing diagrammatic notations based on Euler diagrams are mostly limited in expressiveness to monadic first-order logic with an order predicate. The most expressive monadic diagrammatic notation is known as spider diagrams of order. A primary contribution of this paper is to develop and formalise a second-order diagrammatic logic, called second-order spider diagrams, extending spider diagrams of order. A motivation for this lies in the limited expressiveness of first-order logics. They are incapable of defining a variety of common properties, like 'is even', which are second-order definable. We show that second-order spider diagrams are at least as expressive as monadic second-order logic. This result is proved by giving a method for constructing a second-order spider diagram for any regular expression. Since monadic second-order logic sentences and regular expressions are equivalent in expressive power, this shows second-order spider diagrams can express any sentence of monadic second-order logic.
Keywords: Expressiveness; Spider diagrams; Diagrammatic logic; Second-order logic
Vibes: A visual language for specifying behavioral requirements of algorithms BIBAKFull-Text 350-364
  Gürcan Gülesir; Lodewijk Bergmans; Mehmet Aksit; Klaas van den Berg
Manually verifying the behavior of software systems with respect to a set of requirements is a time-consuming and error-prone task. If the verification is automatically performed by a model checker however, time can be saved, and errors can be prevented. To be able to use a model checker, requirements need to be specified using a formal language. Although temporal logic languages are frequently used for this purpose, they are neither commonly considered to have sufficient usability, nor always naturally suited for specifying behavioral requirements of algorithms. Such requirements can be naturally specified as regular language recognizers such as deterministic finite accepters, which however suffer from poor evolvability: the necessity to re-compute the recognizer whenever the alphabet of the underlying model changes. In this paper, we present the visual language Vibes that both is naturally suited for specifying behavioral requirements of algorithms, and enables the creation of highly evolvable specifications. Based on our observations from controlled experiments with 23 professional software engineers and 21 M.Sc. computer science students, we evaluate the usability of Vibes in terms of its understandability, learnability, and operability. This evaluation suggests that Vibes is an easy-to-use language.
Keywords: State-transition diagrams; Formal methods; Software specification; Visual formalisms
Propagation of constraints along model transformations using triple graph grammars and borrowed context BIBAKFull-Text 365-388
  Hartmut Ehrig; Frank Hermann; Hanna Schözel; Christoph Brandt
Fundamental properties of model transformations based on triple graph grammars (TGGs) have been studied extensively including syntactical correctness, completeness, termination and functional behavior. But up to now, it is an open problem how domain specific properties that are valid for a source model can be preserved along model transformations such that the transformed properties are valid for the derived target model. This question shows up in enterprise modeling. Here, modeling activities related to different domains are handled by different parties, and their models need to be consistent and integrated into one holistic enterprise model later on. So, support for decentralized modeling processes is needed. One technical aspect of the needed support in this case is the (bidirectional) propagation of constraints because that enables one party to understand and check the constraints of another party. Therefore, we analyze in the framework of TGGs how to propagate constraints from a source model to an integrated model and, afterwards, to a target model, such that, whenever the source model satisfies the source constraint, also the integrated and target model satisfy the corresponding integrated and target constraint. In our main new results we show under which conditions this is possible.
Keywords: Model transformation; Graph constraints; Security requirements; Triple graph grammars; Enterprise modeling

Visualisation of Evolving Systems

Guest editor's introduction BIBFull-Text 389
  Philip Cox
Continuous awareness: A visual mobile approach BIBAKFull-Text 390-401
  Cong Chen; Wenyuan Tao; Kang Zhang
Facing the challenges of global distribution in software development, Continuous Coordination constitutes a new coordination paradigm that helps break the communication barriers in distributed teams by providing awareness information and integrating heterogeneous tools. Continuous Awareness is an extension of Continuous Coordination emphasizing continuous awareness support across space and time. Traditional desktop-based approaches are insufficient for the requirements of continuous awareness. Team Radar Mobile takes a visual mobile approach to awareness by extending the visualization of awareness information on desktop platforms to mobile platforms. The concept of continuous awareness and its implementation on multiple platforms are discussed. An experiment has evaluated the visual mobile approach to continuous awareness, and found visualization express awareness information more efficiently than the non-visual approach. Our work also provides experience on mobile visualization.
Keywords: Awareness; Mobile visualization; Continuous awareness; Global software development
Visualization and analysis of 3D time-varying simulations with time lines BIBAKFull-Text 402-418
  Li Yu; Aidong Lu; Wei Chen
This paper presents a time line visualization approach, which allows users to study temporal relationships through encoding their interested data properties to time lines with different shapes and locations. Specifically, our approach extracts key data features as virtual words and uses them to encode various data properties. The distributions of virtual words across time are further applied to study various temporal relationships by generating time lines, which renders sampled time steps as points and temporal sequence as a line. Our approach consists of the three following components. First, we select feature points and collect feature descriptors to build a space of data properties, where virtual words are extracted as representative vectors. Second, the virtual words are applied to characterize feature points and their distribution statistics are used to measure temporal relationships. Third, we demonstrate several methods to visualize time lines flexibly for different data visualization and analysis purposes. We present several case studies to visualize time lines for different data visualization and analysis purposes. Our time line visualization can be used for both summarization and exploration of overall temporal relationships. We demonstrate with examples that time lines can serve as effective exploration, comparison, and visualization tools to study time-varying datasets.
Keywords: Time line; Virtual words; Feature description; Time-varying data visualization

VLC 2013-12 Volume 24 Issue 6

Graph Transformation and Visual Modeling Techniques

Special Issue on Graph Transformation and Visual Modeling Techniques: Guest Editors' introduction BIBFull-Text 419-420
  Andrew Fish; Leen Lambers
Annotation processes for flexible management of contextual information BIBAKFull-Text 421-440
  Paolo Bottoni; Francesco Parisi Presicce
We propose the use of annotations as a way to flexibly enrich a domain of interest with information concerning different contexts of use for its elements. We provide a formal model of annotation in the framework of typed graphs, in which the presence of annotations is reified through nodes and edges of specific types, relating nodes from different domains. This allows the flexible activation and de-activation of annotations, as well as the addition of several annotations from different domains on the same element. We show that annotations give rise to a category, where pushouts are the basic construct for the composition of annotation-related processes. We prove some properties of annotated graphs and discuss examples drawn from several fields.
Keywords: Annotations; Graph transformations; Graph constraints
Model-driven rapid prototyping with programmed graph transformations BIBAKFull-Text 441-462
  Anthony Anjorin; Karsten Saller; Ingo Reimund; Sebastian Oster; Ivan Zorcic; Andy Schürr
Modern software systems are constantly increasing in complexity and supporting the rapid prototyping of such systems has become crucial to check the feasibility of extensions and optimizations, thereby reducing risks and, consequently, the cost of development. As modern software systems are also expected to be reused, extended, and adapted over a much longer lifetime than ever before, ensuring the maintainability of such systems is equally gaining relevance.
   In this paper, we present the development, optimization and maintenance of MoSo-PoLiTe, a framework for Software Product Line (SPL) testing, as a novel case study for rapid prototyping via metamodelling and programmed graph transformations.
   The first part of the case study evaluates the use of programmed graph transformations for optimizing an existing, hand-written system (MoSo-PoLiTe) via rapid prototyping of various strategies. In the second part, we present a complete re-engineering of the hand-written system with programmed graph transformations and provide a critical comparison of both implementations.
   Our results and conclusions indicate that metamodelling and programmed graph transformation are not only suitable techniques for rapid prototyping, but also lead to more maintainable systems.
Keywords: Rapid prototyping; Programmed graph transformations; Metamodelling; Software product lines; Model-driven testing

Regular Articles

GlyphLink: An interactive visualization approach for semantic graphs BIBAKFull-Text 463-471
  Merve Cayli; Murat Can Cobanoglu; Selim Balcisoy
Graph analysis by data visualization involves achieving a series of topology-based tasks. When the graph data belongs to a data domain that contains multiple node and link types, as in the case of semantic graphs, topology-based tasks become more challenging. To reduce visual complexity in semantic graphs, we propose an approach which is based on applying relational operations such as selecting and joining nodes of different types. We use node aggregation to reflect the relational operations to the graph. We introduce glyphs for representing aggregated nodes. Using glyphs lets us encode connectivity information of multiple nodes with a single glyph. We also use visual parameters of the glyph to encode node attributes or type specific information. Rather than doing the operations in the data abstraction layer and presenting the user with the resulting visualization, we propose an interactive approach where the user can iteratively apply the relational operations directly on the visualization. We present the efficiency of our method by the results of a usability study that includes a case study on a subset of the International Movie Database. The results of the controlled experiment in our usability study indicate a statistically significant contribution in reducing the completion time of the evaluation tasks.
Keywords: Graph visualization; Node -- link diagrams; Node aggregation; Relational operations; Glyphs
Creating and evaluating a particle system for music visualization BIBAKFull-Text 472-482
  Joyce Horn Fonteles; Maria Andréia Formico Rodrigues; Victor Emanuel Dias Basso
In this paper, we present a simplified 3D particle system and fast translation algorithm we have designed and implemented to generate real-time animated particle emitter fountains choreographed by a classical music. The approach we used to translate and map the controlling information into the musical fountain animation is also introduced, as well as the process to build the physical model of the music fountains. A proof of concept is implemented to demonstrate the main system's aspects, its feasibility, and that it has met the system's design goals. Moreover, it shows that is possible to observe visual patterns that match the theme of the musical composition, as an example of how the system can be used not only for visual appreciation and entertainment, but also as a possible support tool for music composition. We have also conducted a user study as an evaluation of the system. The results of this have provided us with positive and useful feedback on the effectiveness of our visual mappings as well as further directions to explore.
Keywords: Particle system; Music; Visualization; Animation; Evaluation