Interactive tag maps and tag clouds for the multiscale exploration of large spatio-temporal datasets

'Tag clouds' and 'tag maps' are introduced to represent geographically referenced text. In combination, these aspatial and spatial views are used to explore a large structured spatio-temporal data set by providing overviews and filtering by text and geography. Prototypes are implemented using freely available technologies including Google Earth and Yahoo! 's Tag Map applet. The interactive tag map and tag cloud techniques and the rapid prototyping method used are informally evaluated through successes and limitations encountered. Preliminary evaluation suggests that the techniques may be useful for generating insights when visualizing large data sets containing geo-referenced text strings. The rapid prototyping approach enabled the technique to be developed and evaluated, leading to geovisualization through which a number of ideas were generated. Limitations of this approach are reflected upon. Tag placement, generalisation and prominence at different scales are issues which have come to light in this study that warrant further work

Visualizing Dynamic Memory Allocations

We present a visualization tool for dynamic memory allocation information obtained from instrumenting the runtime allocator used by C programs. The goal of the presented visualization techniques is to convey insight in the dynamic behavior of the allocator. The purpose is to help the allocator designers understand how the performance and working of the allocator depend on the actual allocation scenarios in order to optimize its functionality by decreasing fragmentation and improving response time. We use an orthogonal dense pixel layout of time versus memory space which can show tens of thousands of allocation events on a single screen. We enhance the basic idea with several new techniques: antialiased metric bars for detecting high and low activity areas; cushion cursors for checking correlations of multiple views; and a view to show correlation between program structure (functions) and memory allocations. The presented techniques are demonstrated on data from a real application