Visualization of time varying hierarichal data

["Johannes.Lichtenberger" <Johannes.Lichtenberger@uni-konstanz.de>]

Hello,

would you find it useful to have visualizations of how hierarichal data
(XML) changes over time (several revisions of one XML-file or maybe even
of collections)? I'm going to implemenet a prototype based on our XML
database system and have some ideas.

I think at first I will implement some metrics and visualize how many
changes (inserts and deletes of nodes have been made in every revision)
without showing the hierarchy at all, so that you have an overview. Then
you can pick several revisions and visualize the changes in the
hierarchy itself using a modified radial layout and/or Treemap. Links
based on id/idref attributes can then be visualized with bezier curves
or something like that.

Furthermore it should be possible to select subtrees with XPath
expressions and somehow enlarge them while shrinking other regions. I
suppose I also have to prune the tree initially after some user
specified threshold and then provide ways to move down the hierarchy.

It's going to be my master project and thesis, so what features would
you find useful or what do you think at all?

regards,
Johannes