Cauchy-characteristic extractions (CCE) avoids the errors due to extraction at finite worldtube. The Cauchy and the characteristic approaches have complementary strengths and weaknesses. Unification of the two methods is a promising way of combining the strengths of both formalisms.
Babiuc-Hamilton M. (2009, May). Steps Towards a Nonlinear Cauchy-characteristic Code Patching. Slides presented at Multi-Messenger Relativistic Astrophysics 2009 Conference, Atlanta, GA.