A combinatorial approach to building navigation graphs for dynamic web applications

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 approach 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 a single node in a navigation graph. Grouping pages reduces and bounds the size of a navigation graph for practical applications. Second, assuming that values of individual parameters are supplied by using other techniques or generated manually by the user, we combine parameter values in a way that achieves a well-defined combinatorial coverage called pairwise coverage. Using pairwise coverage can significantly reduce the number of requests that have to be submitted while still achieving effective coverage of the navigation structure. We report a prototype tool called Tansuo, and apply the tool to five open source Web applications. Our empirical results indicate that Tansuo can efficiently generate Web navigation graphs for these applications.