A Note About Universality Theorem as an Enumerative Riemann-Roch Theorem
  The paper is a short supplement of the longer paper "The Algebraic Proof of the Universality Theorem", preprint math.AG/0402045. In this short note, we outline the geometric meaning of Universality theorem (conjecture by Gottsche) as a non-linear extension of surface Riemann-Roch Theorem, inspired by the string theory argument of Yau-Zaslow to probe non-linear information from linear systems of algebraic surfaces.   The universality theorem is an existence result which reflects the topological nature of the Riemann-Roch problem.   We also outline the crucial role that Yau-Zaslow formula has played in our theory. At the end, we list a few open problems related to the algebraic solution of the problem. 
Ai-Ko Liu