Celmar Guimarães da Silva

Visual structures for image browsing

Content-Based Image Retrieval (CBIR) presents several challenges and has been subject to extensive research from many domains, such as image processing or database systems. Database researchers are concerned with indexing and querying, whereas image processing experts worry about extracting appropriate image descriptors. Comparatively little work has been done on designing user interfaces for CBIR systems. This, in turn, has a profound effect on these systems since the concept of image similarity is strongly influenced by user perception. This paper describes an initial effort to fill this gap, combining recent research in CBIR and Information Visualization, studied from a Human-Computer Interface perspective. It presents two visualization techniques based on Spiral and Concentric Rings implemented in a CBIR system to explore query results. The approach is centered on keeping user focus on both the query image, and the most similar retrieved images. Experiments conducted so far suggest that the proposed visualization strategies improves system usability.

An improved visualization-based approach for project portfolio selection

We propose a 2-step interactive approach for solving a project portfolio selection problem as a single-criterium optimization problem. Our approach innovates by using two coordinated charts: an interactive project timeline with drag-and-drop functionalities for project reallocation in time; and an interactive cost and risk chart that combines line charts and bar charts in order to present multidimensional time-based datasets. We also use bar charts related to the allocation of man-hour resources. These functionalities enable users to refine the model that is fed into optimization software in order to achieve results that better correspond to their expectations. We discuss results of a heuristic-based usability evaluation of our prototype, its use in real scenarios, and present preliminary positive feedback from users. We present a visualization approach for a single-criterium optimization problem.We propose an interactive dashboard of costs, risks and project allocation in time.We propose an interactive chart of man-hour data.We present a new cluster-based layout for timelines with draggable events.

A Case Study of the Development of e-Learning Systems Following a Component-based Layered Architecture

The development of flexible, reusable and interoperable LMSs has increasingly attracted the attention of the e-learning community. Considering these issues, the TIDIA-Ae project has been proposing a component-based solution for LMSs development. This article presents a development case study according to the TIDIA-Aes component-based architecture, whose activity was the development of the Portfolio and Weblog tools. The main artifacts obtained in the development process, the solutions adopted for the open issues and the main learned lessons are presented.

PQR sort: using PQR trees for binary matrix reorganization

BackgroundReorganization of rows and columns of a matrix does not modify data but may ease or impair visual analysis of data similarities in this structure, according to Gestalt spatial proximity laws. However, there are a factorial number of permutations of rows and columns. Matrix reordering algorithms, such as 2D sort and Sugiyama-based reordering, permute matrix rows and columns in order to highlight hidden patterns.MethodsWe present PQR sort, a matrix reordering algorithm based on a recent data structure called PQR tree, and compare it with the previous ones in terms of time complexity and quality of reordering, according to predefined evaluation criteria.ResultsWe found that PQR sort is an interesting method for minimizing minimal span loss functions based on Jaccard or simple matching coefficients, specially for a given pattern called Rectnoise with a noise ratio of 0.01 or 0.02 and a matrix size of 100 × 100 or 1,000 × 1,000.ConclusionWe concluded that “PQR sort” is a valid alternative method for matrix reordering, which may also be extended for other visual structures.

Accessibility Guidelines for the Use of Tablets by Elderly: Evaluation of Proposed Changes to WCAG

The aging of Brazilian population increases the importance of the study of accessibility. Tablets devices are winning the market, and the study of their interfaces for the elderly also an important field of research. However, recent studies have found that the WCAG 2.0 do not fully address this scenario. In order to fill this gap, nine new successful criteria for WCAG 2.0 to assist in the detection of accessibility problems in this scenario have been proposed, but they have not been evaluated. This article presents the evaluation of these nine new successful criteria. The methodology was based on recruiting evaluators, separating them into three groups, choosing websites that have presented the problems that gave rise to the new criteria, inspecting the websites and analyzing the results. Results of the accessibility evaluation using the new criteria have shown that they are relevant and help in detecting a greater number of accessibility problems in websites.

A fast feature vector approach for revealing simplex and equi-correlation data patterns in reorderable matrices

Reorderable matrices may be used as support for tabular displays such as heatmaps. Matrix reordering algorithms provide an initial permutation of these matrices, which should help to reveal hidden patterns in the dataset in the visual structure. Some of these algorithms directly permute the data matrix, instead of its row- and column-proximity matrices. We present a data matrix reordering method (feature vector-based sort – FVS), which reorders a data matrix aiming to reveal simplex and equi-correlation patterns. Our approach extracts feature vectors from a data matrix and uses them to calculate row and column permutations of the data matrix. We used FVS for reordering data matrices of distinct real-world scenarios, in which it revealed those patterns. Our experiments with synthetic matrices revealed that FVS is faster than other known matrix-reordering algorithms and produces results of approximately the same quality (in terms of stress function) when these patterns are hidden in the data matrix. We also present some real-world datasets reordered by our algorithm and discuss the patterns that it uncovers.

A Visualization-Based Approach for Project Portfolio Selection

We propose a 2-step interactive approach for solving a project portfolio selection problem as a single-criterium optimization problem. Our approach innovates by using two coordinated charts: an interactive project timeline with drag-and-drop functionalities for project reallocation in time; and an interactive cost and risk chart that combines a line chart and several bar charts in order to present multidimensional time-based datasets. These functionalities enable users to refine the model fed into optimization software in order to achieve results that better correspond to their expectations. We discuss the use of our prototype in real scenarios, and present preliminary positive feedback from users.

Usability heuristics and accessibility guidelines: a comparison of heuristic evaluation and WCAG

The distinction between usability and accessibility becomes convoluted as we focus our analysis in the field of HCI. They were originally conceived as separate concepts and there is no clear comparison between them in the literature. Some authors advocate that these are complementary definitions, while others classify accessibility as a sub-class of usability. Such lack of distinction may pose a challenge to many areas that attempt to implement such concepts such as requirements engineering, possibly leading to redundant implementations or incomplete efforts. Therefore, this work attempts at bridging this gap in the research literature by mapping Nielsens usability heuristics to the W3Cs Web Content Accessibility Guidelines (WCAG). We conclude that there is a strong relationship between them and that it is possible to establish a mapping so that all heuristics are represented by at least one principle and vice versa. Furthermore, we notice that the mapping distribution is non-homogeneous as it focus mainly on three heuristics.

Data mining techniques for water ecotoxicity classification for application on water resources management

Among the various forms of action that promote sustainability, technological innovation can be considered one of the most important. This paper applied data mining techniques to discover knowledge in the field of water quality monitoring data, providing useful and relevant support for decision-making in environmental management systems. At the current stage of research, a predictive modelling technique, known as rule-based classification, was used to find rules that can, based on the values of certain chemical parameters, predict the ecotoxicity level of a water sample. We used data from water analyses from main water bodies of Sao Paulo state in Brazil, from 2005 to 2010. We expect to get a reliable, fast and effective way to predict the ecotoxicity levels of water in rivers, lakes and reservoirs based on analyses of chemical parameters, or indicate the complementarity of these measurements for optimisation of monitoring networks and the consequent improvement natural resources management.

Adapting Heuristic Evaluation to Information Visualization - A Method for Defining a Heuristic Set by Heuristic Grouping

Heuristic evaluation technique is a classical evaluation method in Human-Computer Interaction area. Researchers and software developers broadly use it, given that it is fast, cheap and easy to use. Using it in other areas demands creating a new heuristic set able to identify common problems of these areas. Information Visualization (InfoVis) researchers commonly use this technique with the original usability heuristic set proposed by Nielsen, which does not cover many relevant aspects of InfoVis. InfoVis literature presents sets of guidelines that cover InfoVis concepts, but it does not present most of them as heuristics, or they cover much specific concepts. This work presents a method for defining a set of InfoVis heuristics for use in heuristic evaluation. The method clusters heuristics and guidelines found in a literature review, and creates a new heuristic set based on each group. As a result, we created a new set of 15 generic heuristics, from a set of 62 ones, which we hypothesize that will help evaluators to take into account a broad set of visualization aspects during evaluation with possibly less cognitive effort.