Semi-Supervised Learning of Statistical Models for Natural Language Understanding

Natural language understanding is to specify a computational model that maps sentences to their semantic mean representation. In this paper, we propose a novel framework to train the statistical models without using expensive fully annotated data. In particular, the input of our framework is a set of sentences labeled with abstract semantic annotations. These annotations encode the underlying embedded semantic structural relations without explicit word/semantic tag alignment. The proposed framework can automatically induce derivation rules that map sentences to their semantic meaning representations. The learning frameworkis applied on two statistical models, the conditional random fields (CRFs) and the hidden Markov support vector machines (HM-SVMs). Our experimental results on the DARPA communicator data show that both CRFs and HM-SVMs outperform the baselineapproach, previously proposed hidden vector state (HVS) model which is also trained on abstract semantic annotations. In addition,the proposed framework shows superior performance than two other baseline approaches, a hybrid framework combining HVSand HM-SVMs and discriminative training of HVS, with a relative error reduction rate of about 25% and 15% being achieved in F -measure.