Data-driven sentence generation with non-isomorphic trees

Miguel Ballesteros, Bernd Bohnet, Simon Mille, Leo Wanner

Abstract: Abstract structures from which the generation naturally starts often do not contain any func- tional nodes, while surface-syntactic struc- tures or a chain of tokens in a linearized tree contain all of them. Therefore, data-driven linguistic generation needs to be able to cope with the projection between non-isomorphic structures that differ in their topology and number of nodes. So far, such a projection has been a challenge in data-driven genera- tion and was largely avoided. We present a fully stochastic generator that is able to cope with projection between non-isomorphic structures. The generator, which starts from PropBank-like structures, consists of a cas- cade of SVM-classifier based submodules that map in a series of transitions the input struc- tures onto sentences. The generator has been evaluated for English on the Penn-Treebank and for Spanish on the multi-layered Ancora- UPF corpus.