Enrico Bertini

Appropriating and assessing heuristics for mobile computing

Mobile computing presents formidable challenges not only to the design of applications but also to each and every phase of the systems lifecycle. In particular, the HCI community is still struggling with the challenges that mobile computing poses to evaluation. Expert-based evaluation techniques are well known and they do enable a relatively quick and easy evaluation. Heuristic evaluation, in particular, has been widely applied and investigated, most likely due to its efficiency in detecting most of usability flaws at front of a rather limited investment of time and human resources in the evaluation. However, the capacity of expert-based techniques to capture contextual factors in mobile computing is a major concern. In this paper, we report an effort for realizing usability heuristics appropriate for mobile computing. The effort intends to capture contextual requirements while still drawing from the inexpensive and flexible nature of heuristic-based techniques. This work has been carried out in the context of a research project task geared toward developing a heuristic-based evaluation methodology for mobile computing. This paper describes the methodology that we adopted toward realizing mobile heuristics. It also reports a study that we carried out in order to assess the relevance of the realized mobile heuristics by comparing their performance with that of the standard/traditional usability heuristics. The study yielded positive results in terms of the number of usability flaws identified and the severity ranking assigned.

A unified methodology for the evaluation of accessibility and usability of mobile applications

This article reports a unified methodology developed to evaluate the accessibility and usability of mobile computing applications, which is intended to guarantee universal access as far as possible. As a basis for the methodology, this paper presents an analysis of the accessibility guidelines, conducted to take into account the specificity of mobile systems, as well as a set of usability heuristics, specifically devised for mobile computing. Finally, it presents the results of the application of the proposed methodology to applications that have been semi-automatically developed by the MAIS Designer, a new design tool that provides applications suited to different mobile devices.

Give chance a chance: modeling density to enhance scatter plot quality through random data sampling

The problem of visualizing huge amounts of data is well known in information visualization. Dealing with a large number of items forces almost any kind of Infovis technique to reveal its limits in terms of expressivity and scalability. In this paper we focus on 2D scatter plots, proposing a ‘feature preservation’ approach, based on the idea of modeling the visualization in a virtual space in order to analyze its features (e.g., absolute density, relative density, etc.). In this way we provide a formal framework to measure the visual overlapping, obtaining precise quality metrics about the visualization degradation and devising automatic sampling strategies able to improve the overall image quality. Metrics and algorithms have been improved through suitable user studies.

SpringView: cooperation of radviz and parallel coordinates for view optimization and clutter reduction

In this paper we integrate radviz and parallel coordinates, two methods able to handle multidimensional datasets, exploiting their contrasting characteristics. From on side radviz offers good direct data manipulation (i.e., brushing) techniques and low cluttering but it fails in providing visualization of quantitative information; conversely, parallel coordinates clearly shows the values of data attributes and their ranges but suffers from high cluttering also on small datasets and presents tedious manipulation techniques. We developed a prototype, called SpringView, that allows for simultaneously viewing both radviz and parallel coordinates and implements several useful techniques to manipulate the data, both interactively and, more interestingly, automatically. We challenged our approach against two well know multidimensional datasets, proving its effectiveness.

Quality Metrics for 2D Scatterplot Graphics: Automatically Reducing Visual Clutter

The problem of visualizing huge amounts of data is very well known in the field of Computer Graphics. Visualizing large number of items (the order of millions) forces almost any kind of techniques to reveal its limits in terms of expressivity and scalability. To deal with this problem we propose a ”feature preservation” approach, based on the idea of modelling the final visualization in a virtual space in order to analyze its features (e.g, absolute and relative density, clusters, etc.). Through this approach we provide a formal model to measure the visual clutter resulting from the representation of a large dataset on a physical device, obtaining some figures about the visualization decay and devising an automatic sampling strategy able to preserve relative densities.

Visual quality metrics

The definition and usage of quality metrics for Information Visualization techniques is still an immature field. Several proposals are available but a common view and understanding of this issue is still missing. This paper attempts a first step toward a visual quality metrics systematization, providing a general classification of both metrics and usage purposes. Moreover, the paper explores a quite neglected class of visual quality metrics, namely Feature Preservation Metrics, that allow for evaluating and improving in a novel way the effectiveness of basic Infovis techniques.

The sampling lens: making sense of saturated visualisations

Information visualisation systems frequently have to deal with large amounts of data and this often leads to saturated areas in the display with considerable overplotting. This paper introduces the Sampling Lens, a novel tool that utilises random sampling to reduce the clutter within a moveable region, thus allowing the user to uncover any potentially interesting patterns and trends in the data while still being able to view the sample in context. We demonstrate the versatility of the tool by adding sampling lenses to scatter and parallel co-ordinate visualisations. We also consider some implementation issues and present initial user evaluation results.

By chance is not enough: preserving relative density through nonuniform sampling

Dealing with visualizations containing large data set is a challenging issue and, in the field of information visualization, almost every visual technique reveals its drawback when visualizing large number of items. To deal with this problem we introduce a formal environment, modeling in a virtual space the image features we are interested in (e.g, absolute and relative density, clusters, etc.) and we define some metrics able to characterize the image decay. Such metrics drive our automatic techniques (i.e., not uniform sampling) rescuing the image features and making them visible to the user. In This work we focus on 2D scatter-plots, devising a novel non uniform data sampling strategy able to preserve in an effective way relative densities.

Improving 2D scatterplots effectiveness through sampling, displacement, and user perception

In this paper we present a novel, hybrid, and automatic strategy whose goal is to reduce the 2D scatter plot cluttering. The presented technique relies on a combination of nonuniform sampling and pixel displacement and it is driven by perceptual results coming from a suitable user study. The same results are used to define precise quality metrics that allow for validating our approach.

Mobile devices: Opportunities for users with special needs

Breakthroughs in mobile and wireless technologies have revolutionized the world in virtually every aspect. While much work has been and is being done regarding the opportunities and challenges arising from these technologies, much less exists on the unique opportunities and implications the same devices present and raise to users with special needs. Furthermore, the existing little work is normally specific to only a certain type of disability or device. While addressing a specific type of disability or mobile device has its place, it is also significant to ensure that one is operating based on a holistic perspective/framework of the entire audience of the disabled mobile device users.