UCL+Sheffield at SemEval-2016 Task 8: Imitation learning for AMR parsing with an alpha-bound

We develop a novel transition-based parsing algorithm for the abstract meaning representation parsing task using exact imitation learning, in which the parser learns a statistical model by imitating the actions of an expert on the training data. We then use the imitation learning algorithm DAGGER to improve the performance, and apply an α-bound as a simple noise reduction technique. Our performance on the test set was 60% in F-score, and the performance gains on the development set due to DAGGER was up to 1.1 points of Fscore. The α-bound improved performance by up to 1.8 points.