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== Title ==
Maximum Entropy Summary Trees

== Speaker ==
After receiving his PhD from UC Berkeley, Howard Karloff taught at the
University of Chicago and Georgia Tech before joining AT&T Labs--Research
in 1999. An editor of ACM's Transactions on Algorithms and an ACM Fellow,
he has served on the program committees of numerous conferences, chaired
the 1998 Symposium of Discrete Algorithms (SODA) program committee, was
general chair of the 2012 Symposium on the Theory of Computing (2012) and
will be general chair of STOC 2014. He is the author of numerous journal
and conference articles and the Birkhauser book "Linear Programming."
His research interests span theoretical computer science but extend to
more applied areas of computer science such as databases and networking.


== Abstract ==
Given a very large, node-weighted, rooted tree on, say, n nodes,
if one has only enough space to display a k-node summary of the tree,
what is the most informative way to draw the tree? We define a type of
weighted tree that we call a "summary tree" of the original tree, that
results from aggregating nodes of the original tree subject to certain
constraints. We suggest that the best choice of which summary tree to
use (among those with a fixed number of nodes) is the one that maximizes
the information-theoretic entropy of a natural probability distribution
associated with the summary tree, and we provide a (pseudopolynomial-time)
dynamic-programming algorithm to compute this maximum entropy summary
tree, when the weights are integral. The result is an automated way
to summarize large trees and retain as much information about them as
possible, while using (and displaying) only a fraction of the original
node set. We also provide an additive approximation algorithm and
a greedy heuristic that are faster than the optimal algorithm, and
generalize to trees with real-valued weights.

This is joint work with Ken Shirley and will appear at Eurovis 2013.