As the popularity of XML keeps growing rapidly, XML compliant structured document management becomes an interesting and compelling research area. Query optimization for structured documents stands out as a very challenging issue because of the much enlarged optimization (search) space, which is a consequence of the intrinsic complexity of the underlying data model of structured documents. We therefore propose to apply deterministic transformations on query expressions to most aggressively control the search space and fast achieve a sufficiently improved alternative (if not the optimal) for each incoming query expression. This idea is not just exciting but practically attainable. This paper first provides an overview of our optimization strategy, and then focuses on the implementation issues of our transformation system for structured document query optimization.