Effective performance testing techniques are essential for understanding whether a Webbased system will meet its performance objectives. Such systems have to be characterized in terms of sessions; a session being a sequence of inter-dependent requests submitted by a user. Dependencies arise because some requests depend on the responses of earlier requests in a session. These dependencies should be reflected in the synthetic workloads used to test Web-based systems. This makes performance testing a challenge. This research proposes an approach to address this issue. This approach uses an application model that can be used to obtain valid request sequences representing how users interact with the application. These sequences can be used to automatically construct a synthetic workload with desired characteristics. The application model provides an indirection which allows a common set of workload generation tools for testing different applications. Consequently, less effort is needed in maintaining and developing the tools.