Verb Phrase Anaphora:Do(ing) so with Heuristics (2022)

Abstract: Verb Phrase Anaphora (VPA) is a universal language phenomenon. It can occur in the form of do so phrase, verb phrase ellipsis, etc. Resolving VPA can improve the performance of Dialogue processing systems, Natural Language Generation (NLG), Question Answering (QA) and so on. In this paper, we present a novel computational approach to resolve the specific verb phrase anaphora appearing as do so construct and its lexical variations for the English language. The approach follows a heuristic technique using a combination of parsing from classical NLP, state-of-the-art (SOTA) Generative Pre-trained Transformer (GPT) language model and RoBERTa grammar correction model. The result indicates that our approach can resolve these specific verb phrase anaphora cases with 73.40 F1 score. The data set used for testing the specific verb phrase anaphora cases of do so and doing so is released for research purposes. This module has been used as the last module in a coreference resolution pipeline for a downstream QA task for the electronic home appliances sector.

## introduction anaphora is a linguistic construct used for maintaining coherence in the text without being repetitive. a solution to anaphora resolution (ar) can improve the performance of downstream tasks like dialogue systems, natural language generation (nlg), question answering etc. the process of identifying the linguist element (anaphor) that is referring to a preceding linguistic element (antecedent) in the context is known as anaphora resolution (ar). according to @xcite , anaphoras can be classified as pronominal anaphora, lexical noun phrase anaphora, verb phrase anaphora, adverb anaphora and zero anaphora. the current stateof-the-art systems @xcite @xcite have obtained high accuracy for the most prevalent type of anaphoras i.e. pronominal anaphora and lexical noun phrase anaphora cases. however, verb phrase anaphora, adverb anaphora and zero anaphora still remain unsolved due to the complexities involved in these language phenomena. this paper deals with one such case: verb phrase anaphora (vpa). the verb phrase anaphor is resolved by a preceding verb phrase plus any complement and adjunct as the antecedent. the verb phrase anaphor constructs occur as a combination of so, this, that, it and the same thing along with do. example 1 shows the verb phrase anaphor doing so referring to the verb phrase use energy saver mode as an antecedent. besides antecedent identification, the grammar also enforces a syntactic modification to the antecedent as "using energy saver mode" for resolution in reference to the anaphor. antecedent substituted output: using energy saver mode helps reduce the load on the pocket. ## related work the research on computational anaphora and coreference resolution has seen a paradigm shift from heuristic approaches to machine learning approaches in both nominal-antecedent anaphora @xcite and non nominal-antecedent anaphora @xcite categories. specific to vpa, considerable work is seen in the field of theoretical linguistics for different languages. @xcite investigated verb phrase anaphora as deep or surface anaphora for the english language and @xcite studied the same for the danish language. later, @xcite and wei and hui audrey li (2016) studied the syntactic and semantic challenges of do so construct for the english and mandarin language respectively. in dialogue systems, the problem of ellipsis has been addressed by the use of a supervised discriminative machine learning model @xcite and joint modelling with coreference and question-answering data @xcite . @xcite explored the decomposition of verb phrase ellipsis resolution into computational subtasks. itegulov and lebedeva (2018) experimented with identifying dependent type events for verb phrase anaphora resolution. @xcite used an lstm-siamese net mentionranking model to learn abstract anaphora resolution or discourse deixis. on the data front, datasets like ontonotes (pradhan et al., 2012), wikicoref (ghaddar and langlais, 2016) etc. are the common datasets used for benchmarking the nominal-antecedent anaphora and coreference resolution models. other datasets specifically addressing the verb phrase anaphora cases are aarau corpus @xcite , codi-crac 2021 shared task corpus @xcite and vp ellipsis corpus @xcite . though few instances of do so constructs are available in vpe corpus @xcite , we could not use it for our experiment as our downstream qa system deals with a specific pattern of do so construct. as the vpa constructs are consistently coming to the forefront of dialogue systems and qa systems as a challenge, it motivated us to explore the specific case of do so vpa construct and create a dataset to manage our specific needs. ## result the standard evaluation metrics used for anaphora resolution is link based muc score @xcite , mention based b 3 score @xcite and optimal mapping based ceaf-e score @xcite . we evaluated our result using the standard conll 2012 metric @xcite which is calculated as an average of muc, b-cube and ceaf metrics. the high recall value for muc, b-cube and ceaf metrics indicates that our approach is able to identify the antecedent and its span with higher accuracy over the baseline model. and, the overall average f1 score is showing an improvement of 25.0 value over the baseline. ## conclusion and future work this paper presents a computational heuristic approach to resolve the do so verb phrase anaphora. the approach uses a constituency parser to get all the syntactic components of the text. from the syntactic components, all the verb phrases from preceding text is substituted in place of the verb anaphor to generate the candidate sentences. a pretrained language model is used to select the most probable antecedent. the result shows that our approach can identify the antecedent and its span with good accuracy on the vpa dataset developed for this experiment. the dataset used will be shared for further research. in the future, we plan to resolve the span identification issue in the intra-sentential case of do so construct where no conjunct is used as found in our error analysis. we also plan to investigate if our approach can be extended to other verb phrase anaphora constructs in the english language.