Considering the fact that today some corpora for word segmentation are really large (usually tens of thousands of sentences), it is necessary to obtain the latest CTB and investigate whether and how much does annotation transformation bring improvement to a much higher baseline.
the key idea of co-training is utilize the complementarity of different parsing models to mine additional training data from raw text, while iterative training for annotation transformation emphasizes the iterative optimization of the parellelly annotated corpora used  to train the transformation models.