Modeling the navigation structure of a dynamic web application is a challenging task because of the presence of dynamic pages. In particular, there are two problems to be dealt with: (1) the page explosion problem, i.e., the number of dynamic pages may be huge or even infinite; and (2) the request generation problem, i.e., many dynamic pages may not be reached unless appropriate user requests are supplied. As a user request typically consists of multiple parameter values, the request generation problem can be further divided into two problems: (1) How to select appropriate values for individual parameters? (2) How to effectively combine individual parameter values to generate requests? This paper presents a combinatorial approach to building a navigation graph. The novelty of our is two-fold. First, we use an abstraction scheme to control the page explosion problem. In this scheme, pages that are likely to have the same navigation behavior are grouped together, and are represented as ...