Sequicity: Simplifying Task-oriented Dialogue Systems with Single Sequence-to-Sequence Architectures

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简介

Sequicity: Simplifying Task-oriented Dialogue Systems with Single Sequence-to-Sequence Architectures, acl2018, pdf, pytorch code

本文是针对任务型对话提出的一种end2end的模型，名为Sequicity。该模型是一种seq2seq+Two Stage CopyNet的结构。

优点：

  • 1.相对于pipeline的结构，复杂度低，参数少，训练时间短。
  • 2.针对oov的数据，还能保持不错的实体匹配率。
  • 3.可以同时完成task completion和response generation。

结构细节

Belief Span （bspan）

在Belief Span的术语中：一个slot可以是informable 或者requestable。所谓informable是指这个slot是作为知识库搜索时的限制条件，比如食物类型food_type，如果设定成chinese food，则搜索时返回的餐馆必须是中餐馆；所谓requestable是指这个slot可以被用户指定返回，比如用户需要知道餐馆的类型，slotaddress就会被置为true，后面的回答就必须包含餐馆的地址。

Sequicity

image

模型的输入（图中上层）是上一轮的bspan，上一轮的系统回答，本轮的用户输入；输出（图中下层）是更新的bspan和本轮系统回答。

输入先是过了一个统一的encoder，然后再分别过一个bspan的decoder，再拿这个decoder的结果再过response的decoder，生成最终的response。

上面的两步也正对应着两步的copy net：1.计算生成的词分布和输入的词分布，将二者叠加获得新的词分布，生成bspan decoder的输出；2.将生成的次分布和bsapn decoder的词分布叠加，生成response decoder的词分布。

实验

数据集： CamRest676 (Wen et al., 2017a) and KVRET (Eric and Manning, 2017b)

样例：

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{
        "dial": [
            {
                "turn": 0, 
                "usr": {
                    "transcript": "I need to find an expensive restauant that's in the south section of the city.", 
                    "slu": [
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "pricerange", 
                                    "expensive"
                                ]
                            ]
                        }, 
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "area", 
                                    "south"
                                ]
                            ]
                        }
                    ]
                }, 
                "sys": {
                    "sent": "There are several restaurants in the south part of town that serve expensive food. Do you have a cuisine preference?", 
                    "DA": [
                        "food"
                    ]
                }
            }, 
            {
                "turn": 1, 
                "usr": {
                    "transcript": "No I don't care about the type of cuisine.", 
                    "slu": [
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "pricerange", 
                                    "expensive"
                                ]
                            ]
                        }, 
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "food", 
                                    "dontcare"
                                ]
                            ]
                        }, 
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "area", 
                                    "south"
                                ]
                            ]
                        }
                    ]
                }, 
                "sys": {
                    "sent": "Chiquito Restaurant Bar is a Mexican restaurant located in the south part of town.", 
                    "DA": []
                }
            }, 
            {
                "turn": 2, 
                "usr": {
                    "transcript": "What is their address?", 
                    "slu": [
                        {
                            "act": "request", 
                            "slots": [
                                [
                                    "slot", 
                                    "address"
                                ]
                            ]
                        }, 
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "pricerange", 
                                    "expensive"
                                ]
                            ]
                        }, 
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "area", 
                                    "south"
                                ]
                            ]
                        }, 
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "food", 
                                    "dontcare"
                                ]
                            ]
                        }
                    ]
                }, 
                "sys": {
                    "sent": "There address is 2G Cambridge Leisure Park Cherry Hinton Road Cherry Hinton, it there anything else I can help you with?", 
                    "DA": [
                    ]
                }
            }, 
            {
                "turn": 3, 
                "usr": {
                    "transcript": "What is the food type they serve ?", 
                    "slu": [
                        {
                            "act": "request", 
                            "slots": [
                                [
                                    "slot", 
                                    "food"
                                ]
                            ]
                        }, 
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "area", 
                                    "south"
                                ]
                            ]
                        }, 
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "food", 
                                    "dontcare"
                                ]
                            ]
                        }, 
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "pricerange", 
                                    "expensive"
                                ]
                            ]
                        }
                    ]
                }, 
                "sys": {
                    "sent": "They serve Mexican food .", 
                    "DA": []
                }
            }, 
            {
                "turn": 4, 
                "usr": {
                    "transcript": "Nope, that's what I was looking for. Thanks a lot!", 
                    "slu": [
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "food", 
                                    "dontcare"
                                ]
                            ]
                        }, 
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "pricerange", 
                                    "expensive"
                                ]
                            ]
                        }, 
                        {
                            "act": "inform", 
                            "slots": [
                                [
                                    "area", 
                                    "south"
                                ]
                            ]
                        }
                    ]
                }, 
                "sys": {
                    "sent": "Thank you very much for using the Cambridge Restaurant System.", 
                    "DA": []
                }
            }
        ], 
        "dialogue_id": 0, 
        "finished": true, 
        "goal": {
            "constraints": [
                [
                    "pricerange", 
                    "expensive"
                ], 
                [
                    "area", 
                    "south"
                ]
            ], 
            "request-slots": [
                "address"
            ], 
            "text": "Task 11193: You are looking for an expensive restaurant and it should be in the south part of town. Make sure you get the address of the venue."
        }
    },

指标：

  • BLEU
  • Entity match rate evaluates task completion.
  • Success F1

结果：

指标超过各个baseline模型。