This is the approach taken by IBM Models 4 + ( Brown et al. 1993b ; Och and Ney 2003 ) , and more recently by the LEAF model ( Fraser and Marcu 2007 ) .
a systematic comparison of various statistical alignment models
Franz Josef Och Hermann Ney
One solution to this problem is to add more complexity to the model to better reflect the translation process . This is the approach taken by IBM Models 4 + ( Brown et al. 1993b ; Och and Ney 2003 ) , and more recently by the LEAF model ( Fraser and Marcu 2007 ) . Unfortunately , these changes make the models probabilistically deficient and intractable , requiring approximations and heuristic learning and inference prone to search errors .
This is the approach taken by IBM Models 4 + ( Brown et al. 1993b ; @@CITATION ) , and more recently by the LEAF model ( Fraser and Marcu 2007 ) .