This is an excellent book that provides a systematic treatment of one of the most fundamental concepts in modern probability theory. It will certainly find lots of interest among all mathematicians who work at the interplay of stochastics and analysis."--Karl-Theodor Sturm, University of Bonn"Modern theory of Dirichlet forms is widely considered to be one of the main achievements in the analysis of stochastic process, and the authors of this book are among the world's leading experts in the field."--Michael Rckner, Bielefeld University