nips nips2004 nips2004-165 nips2004-165-reference knowledge-graph by maker-knowledge-mining

165 nips-2004-Semi-supervised Learning on Directed Graphs


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Author: Dengyong Zhou, Thomas Hofmann, Bernhard Schölkopf

Abstract: Given a directed graph in which some of the nodes are labeled, we investigate the question of how to exploit the link structure of the graph to infer the labels of the remaining unlabeled nodes. To that extent we propose a regularization framework for functions defined over nodes of a directed graph that forces the classification function to change slowly on densely linked subgraphs. A powerful, yet computationally simple classification algorithm is derived within the proposed framework. The experimental evaluation on real-world Web classification problems demonstrates encouraging results that validate our approach. 1


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[18] X. Zhu, Z. Ghahramani, and J. Lafferty. Semi-supervised learning using Gaussian fields and harmonic functions. In ICML, 2003. A Proof of Proposition 1 Expand the right site of Equ. (4): ΩA (f ) = f (u)f (v) f 2 (u) − p(u) p(u)p(v) ch ([u, v]) u,v h = f 2 (u) − p(u) ch ([u, v]) u v h ch ([u, v]) u,v h f (u)f (v) . p(u)p(v) (15) By substituting Equ. (3), the first term in the above equality can be rewritten as u v = u h w([h, u])w([h, v]) q(h) h w([h, u]) 2 f (u) = p(u) f 2 (u) p(u) f 2 (u). (16) u In addition, the second term in Equ. (15) can be transformed into u,v h = w([h, u])w([h, v]) f (u)f (v) q(h) p(u)p(v) w([h, u]) w([h, v]) f (v). q(h)p(u) q(h)p(v) f (u) u,v h (17) Substituting Equ. (16) and (17) into (15), we have f 2 (u) − ΩA (f ) = u This completes the proof. f (u) u,v h w([h, u]) w([h, v]) f (v). q(h)p(u) q(h)p(v) (18)