Tree kernels were inspired in part by ideas from Data-Oriented Parsing (Scha, 1990;Bod, 1993), which was in turn motivated by uncertainty about which fragments to include in a grammar.
manual and automatic approaches to inducing tree fragments have recently been found to be useful in an explicit approach to text classification, which employs specific tree fragments as features in standard classifiers (Post, 2011;Wong and Dras, 2011;Swanson and Charniak, 2012).