Monday, February 2, 2009

Graph Theory -- Becoming "Organizing Framework"

Something I've been noting -- both on my own, and in conversations with Jenn Sleeman , who's in touch with the academic world at UMBC -- Graph theory is growing in centrality as a fundamental organizing framework for many current and emerging computational processes.

Specifically, anything more complex than a simple "tuple" (RDF or OWL, etc.), needs to be matched against a graph or partial graph.

One good "integrative" paper is Understanding Belief Propagation and its Generalizations by J.S. Yedidia, W.T. Freeman, and Y. Weiss (2002). One of their points [made right after Eqn. 18, w/r/t Belief Propagation and Graph Theory] is:
"In a practical computation .. one starts with the nodes at the edge of aaph ...
in general, it is easy to see that each message need only be computed once for
singly connected graphs [my note: not all will be singly-connected]. That means
that the whole computation takes a time proportional to the number of links in
thegraph, which is dramatically less than the exponentially large time that
would be required to compute marginal probabilities naively."
There is more -- connecting with Ising, Bethe, and Kikuchi free energy models.

I particularly enjoy the connection with the Kikuchi Cluster Variation Method (CVM), which began in the 1950's as a relatively obscure approach to a more accurate assessment of free energy.