¹Pacific Northwest National Laboratory, Richland, WA, U.S.A

Correspondence: Pak Chung Wong, P.O. Box 999, K7-28, Richland, WA 99352, U.S.A. Tel: +1 509 372 4764; Fax: +1 509 375 3641; E-mail: pak.wong@pnl.gov

Received 9 January 2008; Revised 3 March 2008; Published online 17 April 2008.

Abstract

We present an information visualization tool, known as GreenMax, to visually explore large small-world graphs with up to a million graph nodes on a desktop computer. A major motivation for scanning a small-world graph in such a dynamic fashion is the demanding goal of identifying not just the well-known features but also the unknown–known and unknown–unknown features of the graph. GreenMax uses a highly effective multilevel graph drawing approach to pre-process a large graph by generating a hierarchy of increasingly coarse layouts that later support the dynamic zooming of the graph. This paper describes the graph visualization challenges, elaborates our solution, and evaluates the contributions of GreenMax in the larger context of visual analytics on large small-world graphs. We report the results of two case studies using GreenMax and the results support our claim that we can use GreenMax to locate unexpected features or structures behind a graph.