XCAP and SIP filter chain state transforms via dynamic helper functions for internet multimedia subsystems

The present invention extends a servlet filter chain model to include the ability to dynamically define helper functions. These dynamic helper functions modify the state of an XCAP or SIP request or response as it transitions through the filter chain. The dynamic helper functions are defined via descriptor files that are based on the document type. Each filter in the filter chain has the ability to reference and invoke the helper functions to modify the state of the request and/or response.