Discovery of Emerging Topics between Communities on WWW Naohiro Matsumura 1,3 , Yukio Ohsawa 2,3 , and Mitsuru Ishizuka 1 1 Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113–8656 Japan {matumura, ishizuka}@miv.t.u-tokyo.ac.jp 2 Graduate School of Systems Management, University of Tsukuba, 3-29-1 Otsuka, Bunkyo-ku, Tokyo, 112–0012 Japan osawa@gssm.otsuka.tsukuba.ac.jp 3 TOREST, Japan Science and Technology Corporation, 2-2-11 Tsutsujigaoka, Miyagino-ku, Sendai, Miyagi, 983–0852 Japan Abstract. In the real world, discovering new topics covering profitable items and ideas (e.g., mobile phone, global warming, human genome project, etc) is important and interesting. However, since we cannot com- pletely encode the world surrounding us, it’s difficult to detect such top- ics and their mechanisms in advance. In order to support the detection, we show a method for revealing the structure of WWW by using the KeyGraph algorithm. Empirical results are reported. 1 Introduction In our daily lives, a new topic sometimes become suddenly popular. The topic might seem insignificant at first sight, however, it turns out to match potential needs of us. The Tipping Point [1] describes this kind of phenomenon where a ’little’ thing can make a big difference in the future. For example, how does a novel written by an unknown author become a bestseller? Why did the crime- rate drop so dramatically in New York City? Malcolm Gladwell answers to these questions as follows [1]: ... ideas and behavior and message and products sometimes behave just like outbreaks of infectious disease. They are social epidemics. The Tip- ping Point is an examination of the social epidemics that surround us. The infectious disease usually spreads through the virus. Whereas, we cannot detect the social epidemics(new topics) and their mechanisms in advance since we cannot completely decode the world surrounding us. Detection of a Tipping Point, in face of this obstacle, could be a big chance for our various activities because competitors are not aware of such new topics. We here interpret ’topics’ in the broad sense that cover new items, problems, ideas, and so on. Here we introduce some recent examples of new significant topics: