Yimai Fang


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Prompting for a conversation: How to control a dialog model?
Josef Valvoda | Yimai Fang | David Vandyke
Proceedings of the Second Workshop on When Creative AI Meets Conversational AI

Dialog modelling faces a difficult trade-off. Models are trained on a large amount of text, yet their responses need to be limited to a desired scope and style of a dialog agent. Because the datasets used to achieve the former contain language that is not compatible with the latter, pre-trained dialog models are fine-tuned on smaller curated datasets. However, the fine-tuning process robs them of the ability to produce diverse responses, eventually reducing them to dull conversation partners. In this paper we investigate if prompting can help with mitigating the above trade-off. Specifically, we experiment with conditioning the prompt on the query, rather than training a single prompt for all queries. By following the intuition that freezing the pre-trained language model will conserve its expressivity, we find that compared to fine-tuning, prompting can achieve a higher BLEU score and substantially improve the diversity and novelty of the responses.


Plan-then-Generate: Controlled Data-to-Text Generation via Planning
Yixuan Su | David Vandyke | Sihui Wang | Yimai Fang | Nigel Collier
Findings of the Association for Computational Linguistics: EMNLP 2021

Recent developments in neural networks have led to the advance in data-to-text generation. However, the lack of ability of neural models to control the structure of generated output can be limiting in certain real-world applications. In this study, we propose a novel Plan-then-Generate (PlanGen) framework to improve the controllability of neural data-to-text models. Extensive experiments and analyses are conducted on two benchmark datasets, ToTTo and WebNLG. The results show that our model is able to control both the intra-sentence and inter-sentence structure of the generated output. Furthermore, empirical comparisons against previous state-of-the-art methods show that our model improves the generation quality as well as the output diversity as judged by human and automatic evaluations.


A Generative Model for Joint Natural Language Understanding and Generation
Bo-Hsiang Tseng | Jianpeng Cheng | Yimai Fang | David Vandyke
Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics

Natural language understanding (NLU) and natural language generation (NLG) are two fundamental and related tasks in building task-oriented dialogue systems with opposite objectives: NLU tackles the transformation from natural language to formal representations, whereas NLG does the reverse. A key to success in either task is parallel training data which is expensive to obtain at a large scale. In this work, we propose a generative model which couples NLU and NLG through a shared latent variable. This approach allows us to explore both spaces of natural language and formal representations, and facilitates information sharing through the latent space to eventually benefit NLU and NLG. Our model achieves state-of-the-art performance on two dialogue datasets with both flat and tree-structured formal representations. We also show that the model can be trained in a semi-supervised fashion by utilising unlabelled data to boost its performance.


Improving Argument Overlap for Proposition-Based Summarisation
Yimai Fang | Simone Teufel
Proceedings of the 54th Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers)

A Proposition-Based Abstractive Summariser
Yimai Fang | Haoyue Zhu | Ewa Muszyńska | Alexander Kuhnle | Simone Teufel
Proceedings of COLING 2016, the 26th International Conference on Computational Linguistics: Technical Papers

Abstractive summarisation is not yet common amongst today’s deployed and research systems. Most existing systems either extract sentences or compress individual sentences. In this paper, we present a summariser that works by a different paradigm. It is a further development of an existing summariser that has an incremental, proposition-based content selection process but lacks a natural language (NL) generator for the final output. Using an NL generator, we can now produce the summary text to directly reflect the selected propositions. Our evaluation compares textual quality of our system to the earlier preliminary output method, and also uses ROUGE to compare to various summarisers that use the traditional method of sentence extraction, followed by compression. Our results suggest that cutting out the middle-man of sentence extraction can lead to better abstractive summaries.


A Summariser based on Human Memory Limitations and Lexical Competition
Yimai Fang | Simone Teufel
Proceedings of the 14th Conference of the European Chapter of the Association for Computational Linguistics