Unsupervised head assignment algorithms can be used for the many applications in NLP where information on headedness is needed to convert constituency trees into dependency trees, or to extract head-lexicalised grammars from a constituency treebank.
2 the authors' approach of using EM for inducing latent information in treebanks has led to extremely accurate constituency parsers, that neither make use of nor produce headedness information; see (Petrov et al., 2006) then describe our evaluations of these algorithms.