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Answer Passage Ranking Enhancement Using Shallow Linguistic Features

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Abstract

Question Answering (QA) systems play an important role in decision support systems. Deep neural network-based passage rankers have recently been developed to more effectively rank likely answer-containing passages for QA purposes. These rankers utilize distributed word or sentence embeddings. Such distributed representations mostly carry semantic relatedness of text units in which explicit linguistic features are under-represented. In this paper, we take novel approaches to combine linguistic features (such as different part-of-speech measures) with distributed sentence representations of questions and passages. The QUASAR-T fact-seeking questions and short text passages were used in our experiments to show that while ensembling of deep relevance measures based on pure sentence embedding with linguistic features using several machine learning techniques fails to improve upon the passage ranking performance of our baseline neural network ranker, the concatenation of the same features within the network structure significantly improves the overall performance of passage ranking for QA.
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... In such a pipelined architecture, the effectiveness of passage retrieval and ranking has been shown to consistently have a positive correlation with the overall performance of a QA system [11][12][13]. Recent advances in the QA and passage retrieval domains provide evidence that linguistic features of passages and questions play an important role in improving answer passage retrieval effectiveness [14]. To illustrate this, Table 1 summarizes two examples that show the effect of features such as the number of pronouns, the number of nouns, and the query term coverage, in the correct identification of answers to the respective natural language questions. ...
... every single question. Contrary to existing works in the domain, e.g., those in [11,14], this dynamic passage ranking process, therefore, goes beyond a generic, static model that would be applied across several different questions with the same set of feature importance measures. DEA was originally developed to measure the technical and operational efficiency of Decision Making Units (DMUs) that use multiple inputs to produce multiple outputs [15]. ...
... Such embeddings capture contextual information around any given unit of text in such a way that relationships between semantically related units can be established (for example between words city and Melbourne, laptop and computer). The studies in [11,14,[42][43][44][45][46][47][48], those in [49,50] using Bidirectional Encoder Representations from Transformers (BERT) [51], and the work in [52] using phrase-level learning models and dense representations [53,54] are examples of the utilization of deep neural structures to improve passage retrieval. BERT and dense representations have been used in [55] to overcome the low passage ranking performance issues in the presence of typos in query terms. ...
Article
Question Answering (QA) systems play an important role in today’s human–computer interaction systems. QA performance can be significantly improved using effective answer passage retrieval and ranking techniques. Our focus in this paper is on both non machine learning-based and deep learning-based passage retrieval and ranking systems for QA to leverage linguistic features within the text of questions and passages and improve passage ranking effectiveness. We propose a decoupled linguistic and linear programming-based approach for passage ranking using the Data Envelopment Analysis (DEA) technique to improve over well-established answer passage retrieval techniques. Our method scores passages using information retrieval and deep learning relevance metrics, represents retrieved passages using their relevance scores and several linguistic features, and finally makes use of DEA to re-rank the retrieved list of passages. The high effectiveness and significance of our proposed passage ranking method is demonstrated based on several experiments that we have conducted on a standard benchmark data set.
... Re-ranking with a PLM can be performed with a cross-encoder architecture where the question and passage are passed to an encoder trained to identify their relevance. However, the question-passage pair contains semantic features that can help produce a better re-ranking, see e.g., [16,17]. In this paper, we analyze the use of additional information extraction, from both question and passage and its effect on re-ranking. ...
... A significant difference in the distribution of linguistic features between relevant and irrelevant passages is identified. Linguistic features, like parts of speech, are combined with sentence embedding models using the feature concatenation technique in [17]. This enhances the vector representations of the questions and answer passages. ...
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Passage re-ranking in question answering (QA) systems is a method to reorder a set of retrieved passages, related to a given question so that answer-containing passages are ranked higher than non-answer-containing passages. With recent advances in language models, passage ranking has become more effective due to improved natural language understanding of the relationship between questions and answer passages. With neural network models, question-passage pairs are used to train a cross-encoder that predicts the semantic relevance score of the pairs and is subsequently used to rank retrieved passages. This paper reports on the use of open information extraction (OpenIE) triples in the form \({<subject, verb, object>}\) for questions and passages to enhance answer passage ranking in neural network models. Coverage and overlap scores of question-passage triples are studied and a novel loss function is developed using the proposed triple-based features to better learn a cross-encoder model to rerank passages. Experiments on three benchmark datasets are compared to the baseline BERT and ERNIE models using the proposed loss function demonstrating improved passage re-ranking performance.KeywordsPassage re-rankingInformation extractionPassage retrievalLinked open data
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