Korea, Republic of

Knowledge Graph Completion (KGC) has been recently extended to multiple knowledge graph (KG) structures, initiating new research directions, e.g. static KGC, temporal KGC and few-shot KGC. In this presentation, we will demonstrate, a Seq2Seq generative framework that could tackle different verbalizable graph structures by unifying the representation of KG facts into flat text, regardless of their original form. We will explain each model component we designed to improve the performance and demonstrate the experimental result on multiple KGC benchmarks. At last, we will present the ablation study results which verify the effectiveness of our model design.

COLING 2022

Knowledge Is Flat: A Seq2Seq Generative Framework for Various Knowledge Graph Completion

unified framework

sequence-to-sequence model

knowledge graph completion

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COLING, the International Conference on Computational Linguistics, is one of the premier conferences for the natural language processing and computational linguistics.

technical paper

In this study, we propose a morpheme-based scheme for Korean dependency parsing and adopt the proposed scheme to Universal Dependencies. We present the linguistic rationale that illustrates the motivation and the necessity of adopting the morpheme-based format, and develop scripts that convert between the original format used by Universal Dependencies and the proposed morpheme-based format automatically. The effectiveness of the proposed format for Korean dependency parsing is then testified by both statistical and neural models, including UDPipe and Stanza, with our carefully constructed morpheme-based word embedding for Korean. \textsc{morphUD} outperforms parsing results for all Korean UD treebanks, and we also present detailed error analyses. 


Yet Another Format of Universal Dependencies for Korean

Medical report automatic generation has gained increasing interest recently as a way to help radiologists write reports more efficiently. However, this image-to-text task is rather challenging due to the typical data biases: 1) Normal physiological structures dominate the images, with only tiny abnormalities; 2) Normal descriptions accordingly dominate the reports. Existing methods have attempted to solve these problems, but they neglect to exploit useful information from similar historical cases. In this paper, we propose a novel Cross-modal Contrastive Attention (CMCA) model to capture both visual and semantic information from similar cases, with mainly two modules: a Visual Contrastive Attention Module for refining the unique abnormal regions compared to the retrieved case images; a Cross-modal Attention Module for matching the positive semantic information from the case reports. Extensive experiments on two widely-used benchmarks, IU X-Ray and MIMIC-CXR, demonstrate that the proposed model outperforms the state-of-the-art methods on almost all metrics. Further analyses also validate that our proposed model is able to improve the reports with more accurate abnormal findings and richer descriptions.

Cross-modal Contrastive Attention Model for Medical Report Generation

Named Entity Recognition is the task to locate and classify the entities in the text. However, Unlabeled Entity Problem in NER datasets seriously hinders the improvement of NER performance. This paper proposes SCL-RAI to cope with this problem. Firstly, we decrease the distance of span representations with the same label while increasing it for different ones via span-based contrastive learning, which relieves the ambiguity among entities and improves the robustness of the model over unlabeled entities. Then we propose retrieval augmented inference to mitigate the decision boundary shifting problem. Our method significantly outperforms the previous SOTA method by 4.21% and 8.64% F1-score on two real-world datasets.

SCL-RAI: Span-based Contrastive Learning with Retrieval Augmented Inference for Unlabeled Entity Problem in NER

Multi-hop question generation (QG) is the process of generating answer related questions, which requires aggregating multiple pieces of information and reasoning from different parts of the texts.
This is opposed to single-hop QG which generates questions from sentences containing an answer in a given paragraph. Single-hop QG requires no reasoning or complexity, while multi-hop QG often requires logical reasoning to derive an answer related question, making it a dual task.
Not enough research has been made on the multi-hop QG due to its complexity. 
Also, a question should be created using the question type and words related to the correct answer as a prompt so that multi-hop questions can get more information. In this view, we propose a new type-dependent prompt cycleQAG (cyclic question-answer-generation), with a cycle consistency loss in which QG and Question Answering (QA) are learnt in a cyclic manner. The novelty is that the cycle consistency loss uses the negative cross entropy to generate syntactically diverse questions that enable selecting different word representations. Empirical evaluation on the multi-hop dataset with automatic and human evaluation metrics outperforms the baseline model by about 10.38% based on ROUGE score.

Type-dependent prompt CycleQAG : Cycle consistency for Multi-hop Question Generation

Emotion cause pair extraction (ECPE), as one of the derived subtasks of emotion cause analysis (ECA), shares rich inter-related features with emotion extraction (EE) and cause extraction (CE).Therefore EE and CE are frequently utilized as auxiliary tasks for better feature learning, modeled via multi-task learning (MTL) framework by prior works to achieve state-of-the-art (SoTA) ECPE results. However, existing MTL-based methods either fail to simultaneously model the specific features and the interactive feature in between,or suffer from the inconsistency of label prediction.In this work, we consider addressing the above challenges for improving ECPE by performing two alignment mechanisms with a novel A^2 Net model.We first propose a feature-task alignment to explicitly model the specific emotion-&cause-specific features and the shared interactive feature.Besides, an inter-task alignment is implemented, in which the label distance between the ECPE and the combinations of EE&CE are learned to be narrowed for better label consistency.Evaluations of benchmarks show that our methods outperform current best-performing systems on all ECA subtasks.Further analysis proves the importance of our proposed alignment mechanisms for the task.

Joint Alignment of Multi-Task Feature and Label Spaces for Emotion Cause Pair Extraction

Despite having achieved great success for sentiment analysis, existing neural models struggle with implicit sentiment analysis. This may be due to the fact that they may latch onto spurious correlations (“shortcuts”, e.g., focusing only on explicit sentiment words), resulting in undermining the effectiveness and robustness of the learned model. In this work, we propose a CausaL intervention model for implicit sEntiment ANalysis using instrumental variable (CLEAN). We first review sentiment analysis from a causal perspective and analyze the confounders existing in this task. Then, we
introduce an instrumental variable to eliminate the confounding causal effects, thus extracting the pure causal effect between sentence and sentiment. We compare the proposed CLEAN model with several strong baselines on both the general implicit sentiment analysis and aspect-based implicit sentiment analysis tasks. The results
indicate the great advantages of our model and the efficacy of implicit sentiment reasoning.

Causal Intervention Improves Implicit Sentiment Analysis

Multi-hop reasoning requires aggregating mul- tiple documents to answer a complex question. Existing methods usually decompose the multi- hop question into simpler single-hop questions to solve the problem for illustrating the explain- able reasoning process. However, they ignore grounding on the supporting facts of each rea- soning step, which tends to generate inaccu- rate decompositions. In this paper, we pro- pose an interpretable stepwise reasoning frame- work to incorporate both single-hop supporting sentence identification and single-hop question generation at each intermediate step, and uti- lize the inference of the current hop for the next until reasoning out the final result. We em- ploy a unified reader model for both intermedi- ate hop reasoning and final hop inference and adopt joint optimization for more accurate and robust multi-hop reasoning. We conduct exper- iments on two benchmark datasets HotpotQA and 2WikiMultiHopQA. The results show that our method can effectively boost performance and also yields a better interpretable reasoning process without decomposition supervision.

Locate Then Ask: Interpretable Stepwise Reasoning for Multi-hop Question Answering

We present a subword regularization method for WordPiece, which uses a maximum matching algorithm for tokenization. The proposed method, MaxMatch-Dropout, randomly drops words in a search using the maximum matching algorithm. It realizes finetuning with subword regularization for popular pretrained language models such as BERT-base. The experimental results demonstrate that MaxMatch-Dropout improves the performance of text classification and machine translation tasks as well as other subword regularization methods. Moreover, we provide a comparative analysis of subword regularization methods: subword regularization with SentencePiece (Unigram), BPE-Dropout, and MaxMatch-Dropout.


MaxMatch-Dropout: Subword Regularization for WordPiece

Automatic Essay Scoring (AES) is the task of using the computer to evaluate the quality of essays automatically. Current research on AES focuses on scoring the overall quality or single trait of prompt-specific essays. However, users expect to obtain not only the overall score but also the instant feedback from different traits to help improve their writing. Therefore, we first annotate a multi-trait dataset ACEA including 1220 argumentative essays from four traits, i.e., the essay organization, topic, logic, and language. And then we design a Hierarchical Multi-task Trait Scorer (HMTS) to evaluate the quality of writing by modeling these four traits. Moreover, we propose an inter-sequence attention mechanism to enhance information interaction between different tasks and design the trait-specific features for various tasks in AES. The experimental results on ACEA show that our HMTS can effectively score essays from multiple traits, outperforming several strong baselines.

Automated Chinese Essay Scoring from Multiple Traits

Rule mining is an effective approach for reasoning over knowledge graph (KG). Existing works mainly concentrate on mining rules. However, there might be several rules that could be applied for reasoning for one relation, and how to select appropriate rules for completion of different triples has not been discussed. In this paper, we propose to take the context information into consideration, which helps select suitable rules for the inference tasks. Based on this idea, we propose a transformer-based rule mining approach, Ruleformer. It consists of two blocks: 1) an encoder extracting the context information from subgraph of head entities with modified attention mechanism, and 2) a decoder which aggregates the subgraph information from the encoder output and generates the probability of relations for each step of reasoning. The basic idea behind Ruleformer is regarding rule mining process as a sequence to sequence task. To make the subgraph a sequence input to the encoder and retain the graph structure, we devise a relational attention mechanism in Transformer. The experiment results show the necessity of considering these information in rule mining task and the effectiveness of our model.

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Knowledge Is Flat: A Seq2Seq Generative Framework for Various Knowledge Graph Completion

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Yet Another Format of Universal Dependencies for Korean

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