Grammars & Parsing
To Swap or Not to Swap? Exploiting Dependency Word Pairs for Reordering in Statistical Machine Translation
Hadiwinoto, Christian (National University of Singapore) | Liu, Yang (Tsinghua University) | Ng, Hwee Tou (National University of Singapore)
Reordering poses a major challenge in machine translation (MT) between two languages with significant differences in word order. In this paper, we present a novel reordering approach utilizing sparse features based on dependency word pairs. Each instance of these features captures whether two words, which are related by a dependency link in the source sentence dependency parse tree, follow the same order or are swapped in the translation output. Experiments on Chinese-to-English translation show a statistically significant improvement of 1.21 BLEU point using our approach, compared to a state-of-the-art statistical MT system that incorporates prior reordering approaches.
Labeling the Semantic Roles of Commas
Arivazhagan, Naveen (University of Illinois, Urbana Champaign) | Christodoulopoulos, Christos (University of Illinois, Urbana Champaign) | Roth, Dan (University of Illinois, Urbana Champaign)
Commas and the surrounding sentence structure often express relations that are essential to understanding the meaning of the sentence. This paper proposes a set of relations commas participate in, expanding on previous work in this area, and develops a new dataset annotated with this set of labels. We identify features that are important to achieve a good performance on comma labeling and then develop a machine learning method that achieves high accuracy on identifying comma relations, improving over previous work. Finally, we discuss a variety of possible uses, both as syntactic and discourse-oriented features and constraints for downstream tasks.
Syntactic Skeleton-Based Translation
Xiao, Tong (Northeastern University) | Zhu, Jingbo (Northeastern University) | Zhang, Chunliang (Northeastern University) | Liu, Tongran (Institute of Psychology (CAS))
In this paper we propose an approach to modeling syntactically-motivated skeletal structure of source sentence for machine translation. This model allows for application of high-level syntactic transfer rules and low-level non-syntactic rules. It thus involves fully syntactic, non-syntactic, and partially syntactic derivations via a single grammar and decoding paradigm. On large-scale Chinese-English and English-Chinese translation tasks, we obtain an average improvement of +0.9 BLEU across the newswire and web genres.
Non-Linear Similarity Learning for Compositionality
Tsubaki, Masashi (Nara Institute of Science and Technology) | Duh, Kevin (Johns Hopkins University) | Shimbo, Masashi (Nara Institute of Science and Technology) | Matsumoto, Yuji (Nara Institute of Science and Technology)
Many NLP applications rely on the existence ofsimilarity measures over text data.Although word vector space modelsprovide good similarity measures between words,phrasal and sentential similarities derived from compositionof individual words remain as a difficult problem.In this paper, we propose a new method of ofnon-linear similarity learning for semantic compositionality.In this method, word representations are learnedthrough the similarity learning of sentencesin a high-dimensional space with kernel functions.On the task of predicting the semantic similarity oftwo sentences (SemEval 2014, Task 1),our method outperforms linear baselines,feature engineering approaches,recursive neural networks,and achieve competitive results with long short-term memory models.
Evaluation of Semantic Dependency Labeling Across Domains
Stoyanchev, Svetlana (Interactions Corporation) | Stent, Amanda (Yahoo Labs) | Bangalore, Srinivas (Interactions Corporation)
One of the key concerns in computational semantics is to construct a domain independent semantic representation which captures the richness of natural language, yet can be quickly customized to a specific domain for practical applications. We propose to use generic semantic frames defined in FrameNet, a domain-independent semantic resource, as an intermediate semantic representation for language understanding in dialog systems. In this paper we: (a) outline a novel method for FrameNet-style semantic dependency labeling that builds on a syntactic dependency parse; and (b) compare the accuracy of domain-adapted and generic approaches to semantic parsing for dialog tasks, using a frame-annotated corpus of human-computer dialogs in an airline reservation domain.
A Representation Learning Framework for Multi-Source Transfer Parsing
Guo, Jiang (Harbin Institute of Technology) | Che, Wanxiang (Harbin Institute of Technology) | Yarowsky, David (Johns Hopkins University) | Wang, Haifeng (Baidu Inc.) | Liu, Ting (Harbin Institute of Technology)
Cross-lingual model transfer has been a promising approach for inducing dependency parsers for low-resource languages where annotated treebanks are not available. The major obstacles for the model transfer approach are two-fold: 1. Lexical features are not directly transferable across languages; 2. Target language-specific syntactic structures are difficult to be recovered. To address these two challenges, we present a novel representation learning framework for multi-source transfer parsing. Our framework allows multi-source transfer parsing using full lexical features straightforwardly. By evaluating on the Google universal dependency treebanks (v2.0), our best models yield an absolute improvement of 6.53% in averaged labeled attachment score, as compared with delexicalized multi-source transfer models. We also significantly outperform the state-of-the-art transfer system proposed most recently.
Extracting Biomolecular Interactions Using Semantic Parsing of Biomedical Text
Garg, Sahil (USC Information Sciences Institute) | Galstyan, Aram (USC Information Sciences Institute) | Hermjakob, Ulf (USC Information Sciences Institute) | Marcu, Daniel (USC Information Sciences Institute)
We advance the state of the art in biomolecular interaction extraction with three contributions: (i) We show that deep, Abstract Meaning Representations (AMR) significantly improve the accuracy of a biomolecular interaction extraction system when compared to a baseline that relies solely on surface- and syntax-based features; (ii) In contrast with previous approaches that infer relations on a sentence-by-sentence basis, we expand our framework to enable consistent predictions over sets of sentences (documents); (iii) We further modify and expand a graph kernel learning framework to enable concurrent exploitation of automatically induced AMR (semantic) and dependency structure (syntactic) representations. Our experiments show that our approach yields interaction extraction systems that are more robust in environments where there is a significant mismatch between training and test conditions.
Modeling Evolving Relationships Between Characters in Literary Novels
Chaturvedi, Snigdha (University of Maryland, College Park) | Srivastava, Shashank (Carnegie Mellon University) | III, Hal Daume (University of Maryland, College Park) | Dyer, Chris (Carnegie Mellon University)
Studying characters plays a vital role in computationally representing and interpreting narratives. Unlike previous work, which has focused on inferring character roles, we focus on the problem of modeling their relationships. Rather than assuming a fixed relationship for a character pair, we hypothesize that relationships temporally evolve with the progress of the narrative, and formulate the problem of relationship modeling as a structured prediction problem. We propose a semi-supervised framework to learn relationship sequences from fully as well as partially labeled data. We present a Markovian model capable of accumulating historical beliefs about the relationship and status changes. We use a set of rich linguistic and semantically motivated features that incorporate world knowledge to investigate the textual content of narrative. We empirically demonstrate that such a framework outperforms competitive baselines.
Instructable Intelligent Personal Agent
Azaria, Amos (Carnegie Mellon University) | Krishnamurthy, Jayant (Allen Institute for Artificial Intelligence) | Mitchell, Tom M. (Carnegie Mellon University)
Unlike traditional machine learning methods, humans often learn from natural language instruction. As users become increasingly accustomed to interacting with mobile devices using speech, their interest in instructing these devices in natural language is likely to grow. We introduce our Learning by Instruction Agent (LIA), an intelligent personal agent that users can teach to perform new action sequences to achieve new commands, using solely natural language interaction. LIA uses a CCG semantic parser to ground the semantics of each command in terms of primitive executable procedures defining sensors and effectors of the agent. Given a natural language command that LIA does not understand, it prompts the user to explain how to achieve the command through a sequence of steps, also specified in natural language. A novel lexicon induction algorithm enables LIA to generalize across taught commands, e.g., having been taught how to "forward an email to Alice," LIA can correctly interpret the command "forward this email to Bob." A user study involving email tasks demonstrates that users voluntarily teach LIA new commands, and that these taught commands significantly reduce task completion time. These results demonstrate the potential of natural language instruction as a significant, under-explored paradigm for machine learning.
Dependency Tree Representations of Predicate-Argument Structures
Qiu, Likun (Ludong University and Singapore University of Technology and Design) | Zhang, Yue (Singapore University of Technology and Design) | Zhang, Meishan (Singapore University of Technology and Design)
We present a novel annotation framework for representing predicate-argument structures, which uses dependency trees to encode the syntactic and semantic roles of a sentence simultaneously. The main contribution is a semantic role transmission model, which eliminates the structural gap between syntax and shallow semantics, making them compatible. A Chinese semantic treebank was built under the proposed framework, and the first release containing about 14K sentences is made freely available. The proposed framework enables semantic role labeling to be solved as a sequence labeling task, and experiments show that standard sequence labelers can give competitive performance on the new treebank compared with state-of-the-art graph structure models.