Hierarchical Aggregation for Information Visualization: Overview, Techniques, and Design Guidelines <s> Local Aggregation Control <s> In many contexts, humans often represent their own “neighborhood” in great detail, yet only major landmarks further away. This suggests that such views (“fisheye views”) might be useful for the computer display of large information structures like programs, data bases, online text, etc. This paper explores fisheye views presenting, in turn, naturalistic studies, a general formalism, a specific instantiation, a resulting computer program, example displays and an evaluation. <s> BIB001 </s> Hierarchical Aggregation for Information Visualization: Overview, Techniques, and Design Guidelines <s> Local Aggregation Control <s> Toolglass™ widgets are new user interface tools that can appear, as though on a transparent sheet of glass, between an application and a traditional cursor. They can be positioned with one hand while the other positions the cursor. The widgets provide a rich and concise vocabulary for operating on application objects. These widgets may incorporate visual filters, called Magic Lens™ filters, that modify the presentation of application objects to reveal hidden information, to enhance data of interest, or to suppress distracting information. Together, these tools form a see-through interface that offers many advantages over traditional controls. They provide a new style of interaction that better exploits the user’ s everyday skills. They can reduce steps, cursor motion, and errors. Many widgets can be provided in a user inter face, by designers and by users, without requiring dedicated screen space. In addition, lenses provide rich context -dependent feedback and the ability to view details and context simultaneous ly. Our widgets and lenses can be combined to form operation and viewing macros, and can be used over multiple applications. CR Categories and Subject Descriptors: I.3.6 [Computer Graphics]: Methodology and Techniques- interaction techniques; H.5.2 [Information Interfaces and Presentation]: User Interfaces- interaction styles; I.3.3 [ Computer Graphics]: Picture/Image Generation- viewing algorithms; I.3.4 [Computer Graphics]: Graphics Utilities - graphics editors <s> BIB002 </s> Hierarchical Aggregation for Information Visualization: Overview, Techniques, and Design Guidelines <s> Local Aggregation Control <s> One very effective method for managing large data sets is aggregation or binning. We consider two aggregation methods that are tightly coupled with interactive manipulation and the visual representation of the data. Through this integration we hope to provide effective support for the aggregation process, specifically by enabling: 1) automatic aggregation, 2) continuous change and control of the aggregation level, 3) spatially based aggregates, 4) context maintenance across different aggregate levels, and 5) feedback on the level of aggregation. <s> BIB003 </s> Hierarchical Aggregation for Information Visualization: Overview, Techniques, and Design Guidelines <s> Local Aggregation Control <s> Interactive selection is a critical component in exploratory visualization, allowing users to isolate subsets of the displayed information for highlighting, deleting, analysis, or focussed investigation. Brushing, a popular method for implementing the selection process, has traditionally been performed in either screen space or data space. We introduce the concept of a structure-based brush, which can be used to perform selection in hierarchically structured data sets. Our structure-based brush allows users to navigate hierarchies by specifying focal extents and level-of-detail on a visual representation of the structure. Proximity-based coloring, which maps similar colors to data that are closely related within the structure, helps convey both structural relationships and anomalies. We describe the design and implementation of our structure-based brushing tool. We also validate its usefulness using two distinct hierarchical visualization techniques, namely hierarchical parallel coordinates and tree-maps. <s> BIB004 </s> Hierarchical Aggregation for Information Visualization: Overview, Techniques, and Design Guidelines <s> Local Aggregation Control <s> Our ability to accumulate large, complex (multivariate) data sets has far exceeded our ability to effectively process them in searching for patterns, anomalies and other interesting features. Conventional multivariate visualization techniques generally do not scale well with respect to the size of the data set. The focus of this paper is on the interactive visualization of large multivariate data sets based on a number of novel extensions to the parallel coordinates display technique. We develop a multi-resolution view of the data via hierarchical clustering, and use a variation of parallel coordinates to convey aggregation information for the resulting clusters. Users can then navigate the resulting structure until the desired focus region and level of detail is reached, using our suite of navigational and filtering tools. We describe the design and implementation of our hierarchical parallel coordinates system which is based on extending the XmdvTool system. Lastly, we show examples of the tools and techniques applied to large (hundreds of thousands of records) multivariate data sets. <s> BIB005
As discussed in Section 3.4, it is, sometimes, useful to perform unbalanced rendering of the aggregate hierarchy to reveal different amounts of detail for different regions of the visualization in a focus+context BIB001 ,  fashion (Fig. 5) . Local aggregation control gives the user control over this process in different ways. For example, one form of local aggregation control may be to allow the user to directly select which part of the aggregate hierarchy to expand or collapse by, for example, simply clicking on the visual aggregates in the display (leftclick for expand, right-click for collapse). Another instance of this type of interaction may include directly controlling the type of rendering traversal (Section 3.4) to perform, or parameters of the current traversal (cutoffs, start points, current level, etc). In this case, selecting the region of interest becomes part of the problem. While rubberband selection in screen space is the most common approach, structure-based brushes BIB004 support filtering whole branches of the aggregate hierarchy based on its structure. Chuah BIB003 describe the use of Magic Lenses BIB002 for local aggregation control. On a related note, the dynamic masking BIB005 technique interactively fades out unselected regions in favor of selected regions. 