Yukio Ohsawa

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In this paper, we present an algorithm for extracting keywords representing the asserted main point in a document, without relying on external devices such as natural language processing tools or a document corpus. Our algorithm KeyGraph is based on the segmentation of a graph, representing the co-occurrence between terms in a document, into clusters. Each(More)
Experts of chance discovery have recognized a new class of problems where the previous methods fail to visualize a latent structure behind observation. There are invisible events which play an important role in the dynamics of visible events. An invisible leader in a communication network is a typical example. Such an event is named a dark event. A novel(More)
Chance discovery is to become aware of a chance and to explain its significance, especially if the chance is rare and its significance is unnoticed. This direction matches with various real requirements in human life. This paper presents the significance, viewpoints, theories, methods, and future work of chance discovery. Three keys for the progress are(More)
“2channel” is the most popular online-community site in Japan, where millions of people are discussing or chitchatting about various topics. The communication in 2channel shows dynamic social phenomena such as positive/negative communication, polarization of opinions, slander called flaming, etc. In this paper, we assume the existence of underlying(More)
The small world topology is known widespread in biological, social and man-made systems. This paper shows that the small world structure also exists in documents, such as papers. A document is represented by a network; the nodes represent terms, and the edges represent the co-occurrence of terms. This network is shown to have the characteristics of being(More)
The small world topology is known widespread in biological, social and man-made systems. This paper shows that the small world structure also exists in documents, such as papers. A document is represented by a network; the nodes represent terms, and the edges represent the co-occurrence of terms. This network is shown to have the characteristics of being(More)
The pages and hyperlinks of the World Wide Web may be viewed as nodes and edges in a directed graph. In this paper, we propose a new definition of the distance between two pages, called average-clicks. It is based on the probability to click a link through random surfing. We compare the average-clicks measure to the classical measure of clicks between two(More)