  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.
