The Turbine processing pipeline is modeled after the pipeline found in Tomcat 4.0.1 (Catalina), and after the module architecture found in Apache httpd. It is extensible both laterally and vertically via Valve additions and default Valve implementations (respectively). Even the semantics of the default Turbine Pipeline (ClassicPipeline) can be changed by replacing or extending the implementation with a custom one.

As with Catalina, Turbine's Pipeline and Valve configuration is setup via XML: `<pipeline name="default"> <valves> <valve>org.apache.turbine.pipeline.DetermineActionValve</valve> <valve>org.apache.turbine.pipeline.DetermineTargetValve</valve> <valve>org.apache.turbine.pipeline.DefaultSessionTimeoutValve</valve> <valve>org.apache.turbine.pipeline.DefaultLoginValve</valve> <valve>org.apache.turbine.pipeline.DefaultSessionValidationValve</valve> <valve>org.apache.turbine.pipeline.DefaultACLCreationValve</valve> <valve>org.apache.turbine.pipeline.ExecutePageValve</valve> <valve>org.apache.turbine.pipeline.CleanUpValve</valve> <valve>org.apache.turbine.pipeline.DetermineRedirectRequestedValve</valve> </valves> </pipeline>`

Please direct all comments, fixes, and enhancements to the development list.