Maylis Delest

Tree Visualisation and Navigation Clues for Information Visualisation

Information visualisation often requires good navigation aids on large trees, which represent the underlying abstract information. Using trees for information visualisation requires novel user interface techniques, visual clues, and navigational aids. This paper describes a visual clue: using the so‐called Strahler numbers, a map is provided that indicates which parts of the tree are interesting. A second idea is that of “folding” away subtrees that are too “different” in some sense, thereby reducing the visual complexity of the tree. Examples are given demonstrating these techniques, and what the further challenges in this area are.

Retrieval of objects in video by similarity based on graph matching

In this paper, we tackle the problem of matching of objects in video in the context of the rough indexing paradigm. The approach developed is based on matching of region adjacency graphs (RAG) of pre-segmented objects. In the context of the rough indexing paradigm, the video data are of very low resolution and segmentation is consequently inaccurate. Hence the RAGs vary with the time. The contribution of this paper is a graph matching method for such RAGs based on an improvement of relaxation labelling techniques. In this method, adjustments of similarity between regions according to neighborhood consistency compensate for the inaccuracy of segmentation. The approach demonstrates promising performance on real sequences when compared to another region-based technique.

Latour - a tree visualisation system

This paper presents some of the most important features of a tree visualisation system called Latour, developed for the purposes of information visualisation. This system includes a number of interesting and unique characteristics, for example the provision for visual cues based on complexity metrics on graphs, which represent general principles that, in our view, graph based information visualisation systems should generally offer.

New Strahler numbers for rooted plane trees

In this paper, wepresent an extension of Strahler numbers to rooted plane trees. Several asymptotic properties are proved; others are conjectured. We also describe several applications of this extension.

Efficient drawing of RNA secondary structure

In this paper, we propose a new layout algorithm that draws the secondary structure of a Ribonucleic Acid (RNA) automatically according to some of the biologists’ aesthetic criteria. Such layout insures that two equivalent structures (or sub-structures) are drawn in a same and planar way. In order to allow a visual comparison of two RNAs, we use an heuristic that places the biggest similar part of the two structures in the same position and orientation.

Exploring InfoVis Publication History with Tulip

We show the structure of the InfoVis publications dataset using Tulip, a scalable open-source visualization system for graphs and trees. Tulip supports interactive navigation and many options for layout. Subgraphs of the full dataset can be created interactively or using a wide set of algorithms based on graph theory and combinatorics, including several kinds of clustering. We found that convolution clustering and small world clustering were particularly effective at showing the structure of the InfoVis publications dataset, as was coloring by the Strahler metric.

DAG-based visual interfaces for navigation in indexed video content

Indexing and segmenting of video content by motion, color and texture has been intensively explored leading to a commonly used representation in a storyboard. In this paper, a novel method of visualization of video content is proposed. First of all, the content is segmented into shots, and then a spatio-temporal color signature of shots, based on color distribution in the frames, is proposed. This spatio-temporal color signature serves as a basis for graph clustering and graph visualization tools. Those, integrated in a platform for visualization of huge graphs, Tulip, supply an exciting graph-based navigation interface for multimedia content. The results obtained on feature documentaries are promising.

Assessing the quality of multilevel graph clustering

Abstract“Lifting up” a non-hierarchical approach to handle hierarchical clustering by iteratively applying the approach to hierarchically cluster a graph is a popular strategy. However, these lifted iterative strategies cannot reasonably guide the overall nesting process precisely because they fail to evaluate the very hierarchical character of the clustering they produce. In this study, we develop a criterion that can evaluate the quality of the subgraph hierarchy. The multilevel criterion we present and discuss in this paper generalizes a measure designed for a one-level (flat) graph clustering to take nesting of the clusters into account. We borrow ideas from standard techniques in algebraic combinatorics and exploit a variable

A Heuristic for the Retrieval of Objects in Low Resolution Video

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