It is most appropriate that the first volume to appear in the series "Advanced Applications in Pattern Recognition" should be this monograph by Nagao and Matsuyama. The work described here is a deep unification and synthesis of the two fundamental approaches to pat­ tern recognition: numerical (also known as "statistical") and struc­ tural ("linguistic," "syntactic"). The power and unity of the meth­ odology flow from the apparently effortless and natural use of the knowledge-base framework illuminated by the best results of artificial intelligence research. An integral part of the work is the algorithmic solution of many hitherto incompletely or clumsily treated problems. It was on the occasion of a laboratory