Sebastien Rufiange

Assistant Professor
Pau, France

DiffAni: Visualizing Dynamic Graphs with a Hybrid of Difference Maps and Animation

Visualization of dynamically changing networks (graphs) is a significant challenge for researchers. Previous work has experimentally compared animation, small multiples, and other techniques, and found trade-offs between these. One potential way to avoid such trade-offs is to combine previous techniques in a hybrid visualization. We present two taxonomies of visualizations of dynamic graphs: one of non-hybrid techniques, and one of hybrid techniques. We also describe a prototype, called DiffAni, that allows a graph to be visualized as a sequence of three kinds of tiles: diff tiles that show difference maps over some time interval, animation tiles that show the evolution of the graph over some time interval, and small multiple tiles that show the graph state at an individual time slice.  This sequence of tiles is ordered by time and covers all time slices in the data. An experimental evaluation of DiffAni shows that our hybrid approach has advantages over non-hybrid techniques in certain cases.

Treematrix: A Hybrid Visualization of Compound Graphs

We present a hybrid visualization technique for compound graphs (i.e. networks with a hierarchical clustering defined on the nodes) that combines the use of adjacency matrices, node-link and arc diagrams to show the graph, and also combines the use of nested inclusion and icicle diagrams to show the hierarchical clustering. The graph visualized with our technique may have edges that are weighted and/or directed. We first explore the design space of visualizations of compound graphs and present a taxonomy of hybrid visualization techniques. We then present our prototype, which allows clusters (i.e. subtrees) of nodes to be grouped into matrices or split apart using a radial menu. We also demonstrate how our prototype can be used in the software engineering domain, and compare it to the commercial matrix-based visualization tool Lattix using a qualitative user study.

Change impact study using data mining techniques

A common problem in software engineering is to find the right balance between quality and cost, while delivering on time. Needs and technology are evolving faster than our skill to manage such projects. To manage and implement efficiently these change requests can affect the software quality and maintenance costs.

In this study, we used several data mining techniques (classification and regression) to find a relationship between change impact (e.g. lines of code, number of modified files) and software design measures. We found out which attributes seems to have more impact on the maintenance effort. The data was collected from open-source projects, but a larger scale study is currently being done.

Hybrid visualization for hierarchical links

Compound graphs are often useful for modeling components of hierarchical systems. While node-link diagrams can be used to visualize these graphs, adjacency matrices have the advantage of eliminating occlusion between edges, even in dense networks. However, matrices do not reveal the hierarchy in a compound graph. To address this issue, we propose a novel hybrid visualization technique that combines an adjacency matrix with treemaps displaying portions of the hierarchy. A prototype is presented that illustrates these ideas and supports visualization of digraphs with weighted edges. Interaction techniques allow the user to reorganize the hierarchical groupings of elements and facilitates the exploration of links within the network. For example, in software engineering, the prototype enables browsing of links between source code modules to help discover the architecture of the software.

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