Yumi Yamaguchi

Hierarchical data visualization using a fast rectangle-packing algorithm

We present a technique for the representation of large-scale hierarchical data which aims to provide good overviews of complete structures and the content of the data in one display space. The technique represents the data by using nested rectangles. It first packs icons or thumbnails of the lowest-level data and then generates rectangular borders that enclose the packed data. It repeats the process of generating rectangles that enclose the lower-level rectangles until the highest-level rectangles are packed. We present two rectangle-packing algorithms for placing items of hierarchical data onto display spaces. The algorithms refer to Delaunay triangular meshes connecting the centers of rectangles to find gaps where rectangles can be placed. The first algorithm places rectangles where they do not overlap each other and where the extension of the layout area is minimal. The second algorithm places rectangles by referring to templates describing the ideal positions for nodes of input data. It places rectangles where they do not overlap each other and where the combination of the layout area and the distances between the positions described in the template and the actual positions is minimal. It can smoothly represent time-varying data by referring to templates that describe previous layout results. It is also suitable for semantics-based or design-based data layout by generating templates according to the semantics or design.

Generic Security Policy Transformation Framework for WS-Security

Model-driven security is a framework to configure WS-security easily. It generates a security policy written in WS-security policy to be transformed into platform-specific configuration files. Since the WS-security policy specification is quite complicated, it is difficult to directly map between a security policy and a configuration. We propose a generic security policy transformation framework using an intermediate model. The intermediate model structure is designed based on the WS-security message structure, because both a security policy and the configuration files correspond to one WS-security message, even though the WS-security policy is flexible in specifying security requirements. Our contributions are simpler transformation rules compared to direct mapping, the support for various platforms, and more flexible updates if the WS-security policy specification changes. We demonstrate the transformation using the intermediate model for WebSphere application server 6.0.

Easy-To-Use Programming Model for Web Services Security

Even with a support tool, setting up a Web services security (WS-Security) configuration can be difficult for people who are not familiar with WS-Security. Some of the reasons are that the WS-Security is a very rich specification with many options and often the processing is complicated. This paper introduces an application programming model (WSSAPI) to simplify the programming experience for end users. It was designed by looking at WS-Security processing from an abstract level. Also, it is designed to consider correctness, efficiency, usability, flexibility, portability, and extensibility. End users just follow the six-step programming model provided in WSSAPI to configure WS-Security. The comparison of WSSAPI to others, like WSS4J, WSE, and JSR-105 shows that it is much easier for end users to use WSSAPI. In this paper, existing APIs for WS-Security are reviewed and compared with WSSAPI to evaluate the ease of use and utility.

Topologically-Accentuated Volume Rendering

In spite of many attempts at making volume visualization popular, it is still a hard task for novice users to adjust rendering-related parameter values for generating informative images. In our previous study, we took advantage of a 3D field topology analysis for semi-automatic design of transfer functions. In this paper, we address four specific issues to adapt the method for dealing with real world datasets. A medical CT-scanned dataset is used to prove the feasibility of the extended method.

A Topological Analysis Approach to Dynamic Volume Data Mining

This paper takes advantage of a 3D field topology analysis for automating transfer function design aiming at volume data mining. The conventional Reeb graph-based approach to describe the topological features of 3D surfaces is extended to capture the topological skeleton of a volumetric field. Based on the analysis results, which are represented in the form of hyper Reeb graph, we propose two principles to design appropriate color/opacity transfer functions for direct volume rendering. Feasibility study of the present methodology is performed with a large scale 4D simulated dataset from atomic collision research. In analyzing the dynamic volume data, it turned out to be effective to use transfer functions designed appropriately at each time step. The basic idea of another approach with a higher order hyper Reeb graph to dynamic volume data mining is also discussed.