Jens Gerken

IPSep-CoLa: An Incremental Procedure for Separation Constraint Layout of Graphs

We extend the popular force-directed approach to network (or graph) layout to allow separation constraints, which enforce a minimum horizontal or vertical separation between selected pairs of nodes. This simple class of linear constraints is expressive enough to satisfy a wide variety of application-specific layout requirements, including: layout of directed graphs to better show flow; layout with non-overlapping node labels; and layout of graphs with grouped nodes (called clusters). In the stress majorization force-directed layout process, separation constraints can be treated as a quadratic programming problem. We give an incremental algorithm based on gradient projection for efficiently solving this problem. The algorithm is considerably faster than using generic constraint optimization techniques and is comparable in speed to unconstrained stress majorization. We demonstrate the utility of our technique with sample data from a number of practical applications including gene-activation networks, terrorist networks and visualization of high-dimensional data.Existing information-visualization techniques that target small screens are usually limited to exploring a few hundred items. In this article we present a scatterplot tool for personal digital assistants that allows the handling of many thousands of items. The applications scalability is achieved by incorporating two alternative interaction techniques: a geometric-semantic zoom that provides smooth transition between overview and detail, and a fisheye distortion that displays the focus and context regions of the scatterplot in a single view. A user study with 24 participants was conducted to compare the usability and efficiency of both techniques when searching a book database containing 7500 items. The study was run on a pen-driven Wacom board simulating a PDA interface. While the results showed no significant difference in task-completion times, a clear majority of 20 users preferred the fisheye view over the zoom interaction. In addition, other dependent variables such as user satisfaction and subjective rating of orientation and navigation support revealed a preference for the fisheye distortion. These findings partly contradict related research and indicate that, when using a small screen, users place higher value on the ability to preserve navigational context than they do on the ease of use of a simplistic, metaphor-based interaction style

Usability of overview-supported zooming on small screens with regard to individual differences in spatial ability

While zoomable user interfaces can improve the usability of applications by easing data access, a drawback is that some users tend to become lost after they have zoomed in. Previous studies indicate that this effect could be related to individual differences in spatial ability. To overcome such orientation problems, many desktop applications feature an additional overview window showing a miniature of the entire information space. Small devices, however, have a very limited screen real estate and incorporating an overview window often means pruning the size of the detail view considerably. Given this context, we report the results of a user study in which 24 participants solved search tasks by using two zoomable scatterplot applications on a PDA - one of the applications featured an overview, the other relied solely on the detail view. In contrast to similar studies for desktop applications, there was no significant difference in user preference between the interfaces. On the other hand, participants solved search tasks faster without the overview. This indicates that, on small screens, a larger detail view can outweigh the benefits gained from an overview window. Individual differences in spatial ability did not have a significant effect on task-completion times although results suggest that participants with higher spatial ability were slowed down by the overview more than low spatial-ability users.

Design and Implementation of Post-WIMP Distributed User Interfaces with ZOIL

“Interactive spaces” are physical environments or rooms for collaborative work that are augmented with ubiquitous computing technology. Their purpose is to enable a computer-supported collaboration between multiple users that is based on a seamless use of different devices for natural “post-WIMP” interaction (e.g., multitouch walls, interactive tabletops, tablet PCs, or digital pen and paper). However, to this day, there are no well-established guidelines or toolkits for designing and implementing such distributed user interfaces (DUIs). Therefore, this article introduces the Zoomable Object-Oriented Information Landscape (ZOIL), a novel design approach and software framework for post-WIMP DUIs in interactive spaces. In the following, the ZOIL design principles are first introduced and illustrated. They provide recommendations and examples of DUI interaction design for interactive spaces. Then the different software patterns and architectures that have been employed for implementing the open-source ZOIL software framework are described. This framework facilitates the implementation of ZOILs design principles in practice. Lessons learned from ZOILs implementation are shared, and the implementation is discussed and compared with related work and approaches. The results of an evaluation of ZOIL with designers and developers conclude the article.

MedioVis – a user-centred library metadata browser

MedioVis is a visual information seeking system which was designed especially for library data. The objective target was to create a system which simplifies and optimizes the users information seeking process and thus further motivates the user to browse in the library stock. To enhance the motivation special attention was given to consider joy of use aspects during the design of the user interface. The primary user interface design is based on multiple coordinated views to offer a great variety of exploration possibilities in a direct-manipulative manner. To accomplish a self-explanatory usability of the system for non-expert users, the development was accompanied by continuous user tests with casual and regular library users. At the end of the development process a comprehensive summative evaluation was conducted, comparing efficiency and joy of use of the existing web-based catalogue system KOALA of the library of the University of Konstanz with the MedioVis system. The results of this comparative evaluation show a significant improvement of the efficiency of the information seeking process with the help of MedioVis. The users also rated MedioVis significantly better in all dimensions of its hedonic quality and appeal compared with KOALA.

HyperGrid - Accessing Complex Information Spaces

In this paper, we describe a new interaction and visualization concept for non-expert users to easily access complex heterogeneous information spaces. The HyperGrid combines well-known table visualizations with zoomable user interface concepts to provide a two-dimensional grid as an access tool to multi-dimensional and relational data. It allows the presentation of attributes of multiple data types, various modalities and various levels of detail in a compact and consistent visual structure. Our concept is illustrated by a use-case based on our experiences and evaluations from preceding projects in the field of visual information seeking systems.

The concept maps method as a tool to evaluate the usability of APIs

Application programming interfaces (APIs) are the interfaces to existing code structures, such as widgets, frameworks, or toolkits. Therefore, they very much do have an impact on the quality of the resulting system. So, ensuring that developers can make the most out of them is an important challenge. However standard usability evaluation methods as known from HCI have limitations in grasping the interaction between developer and API as most IDEs (essentially the GUI) capture only part of it. In this paper we present the Concept Map method to study the usability of an API over time. This allows us to elicit the mental model of a programmer when using an API and thereby identify usability issues and learning barriers and their development over time.

Model-based design and implementation of interactive spaces for information interaction

Interactive spaces with multiple networked devices and interactive surfaces are an effective means to support multi-user collocated collaboration. In these spaces, surfaces like tablet PCs, tabletops, or display walls can be combined to allow users to interact naturally with their personal or shared information, e.g. during presentation, discussion, or annotation. However, designing and implementing such interactive spaces is a challenging task due to the lack of appropriate interaction abstractions and the shortcomings of current user interface toolkits. We believe that these challenges can be addressed by revisiting model-based design techniques for object-oriented user interfaces (OOUI). We discuss the potential of OOUIs for the design of interactive spaces and introduce our own object-oriented design and implementation approach. Furthermore we introduce the ZOIL (Zoomable Object-Oriented Information Landscape) paradigm that we have used as an experimental testbed. While our approach does not provide automated model-driven procedures to create user interfaces without human intervention, we illustrate how it provides efficient support throughout design and implementation. We conclude with the results from a case study in which we collected empirical data on the utility and ease of use of our approach.

Hidden details of negotiation: the mechanics of reality-based collaboration in information seeking

Social activities such as collaborative work and group negotiation can be an essential part of information seeking processes. However, they are not sufficiently supported by todays information systems as they focus on individual users working with PCs. Reality-based UIs with their increased emphasis on social, tangible, and surface computing have the potential to tackle this problem. By blending characteristics of real-world interaction and social qualities with the advantages of virtual computer systems, they inherently change the possibilities for collaboration, but until now this phenomenon has not been explored sufficiently. Therefore, this paper presents an experimental user study that aims at clarifying the impact such reality-based UIs and its characteristics have on collaborative information seeking processes. Two different UIs have been developed for the purpose of this study. One is based on an interactive multi-touch tabletop in combination with on-screen tangibles, therefore qualifying as a reality-based UI, while the other interface uses three synchronized PCs each controlled by keyboard and mouse. A comparative user study with 75 participants in groups of three was carried out to observe fundamental information seeking tasks for co-located collaboration. The study shows essential differences of emerging group behavior, especially in terms of role perception and seeking strategies depending on the two different UIs.

Pocket Bee: a multi-modal diary for field research

In this paper we present Pocket Bee, a multi-modal diary tool that allows researchers to remotely collect rich and in-depth data in the field. Based on the Android smart phone platform, we especially focused on an easy to use user interface. We introduce the notion of core questions that serve as cognitive triggers for pre-defined events. Multiple modalities allow participants to compose notes in the most appropriate and convenient way. Instant network synchronization allows researchers to view and analyze the data on-the-fly while also being able to create new tasks or questionnaires during an ongoing study. These can also be linked to certain trigger events, such as time and date. Thereby, Pocket Bee supports diary and Experience Sampling (ESM) studies. The system was developed in a user-centered design process and its potential value is described in a scenario of use illustrating an upcoming study.

Can "touch" get annoying?

While touch interaction with tabletops is now widely accepted as a very natural and intuitive form of input, only little research has been carried out to understand whether and how it might interfere with our natural ways of gestural communication. This poster presents a study that aims at understanding the importance of touching physical and virtual artifacts during discussion or collaboration around a table. Furthermore, it focuses on how users compensate for conflicts between non-interactivity and interactivity created by unintended touch interaction when using a multi-touch enabled tabletop. In our study, we asked participants to explain illustrations of technical or physical mechanisms, such as the workings of an airplane wing. We observed whether and how they used gestures to do so on a touch sensitive Microsoft Surface tabletop and on a sheet of paper. Our results suggest that touching is an essential part of such an activity and that the compensation strategies people adapt to avoid conflicts may reduce precision of communication and increase the physical strain on the user.