自然語言檢索是使用人類語言問句搜尋答案。其目的是要擷取適合使用者的答案。相較於一般的短語查詢，自然語言問句查詢則是更能直覺的呈現出使用者的問題。例如，問句「台南哪裡適合約會?」。但現今的搜尋引擎在自然語言檢索方面的表現往往不佳，導致使用者必須花大部分的時間在瀏覽出現部分詞彙網頁答案。在本論文，自然語言問句搜尋被定義為使用者想獲得一系列同性質的實體，並與ROSE等人提出條列式資訊目的定義相符。
在仔細的分析自然語言問句後，問句結構可以被分為問句上下文、問句實體、問句活動以及問句情緒。並且我們發現到了活動跟情緒之間有一些關係存在，提出了一個自動化的方式找出兩者的關聯來擴充問句。我們基於使用者需求分析問句中的活動以及隱含的情緒，並推薦適合的實體。我們使用適合中文的問句分析演算法辨識以上問句結構特徵。至於答案結構可以被分為上下文的證明頁面、實體類型、實體活動以及實體情緒詞總結。我們利用問句結構和答案結構的關係，結合實際上的網路的評價意見，建構出以活動及情緒為基礎的實體排序模型(ASERM)來改善實體搜尋。
實驗結果顯示我們提出的模型ASERM可以幫助使用者找到他們想要的實體。也顯示出我們的系統著實能增進實體搜尋的效能

Natural language search is to use human language questions as query to search answers. The task of natural language search is to extract suitable answers for users. Compare with short query, Natural language query users can directly submit their query intents. For example, the question, “Which places in Tainan are appropriate for dating?” But conventional search engines can’t efficiently process natural language queries and users can’t get good search results. So users need to spend lots of time on browsing and filter the result pages, which may involve some noise information. In those natural language question search, user wants to obtain a list of homogeneous entities. According to Rose et al. proposed list-informational goal definition, natural language question search is properly matched list-informational goal.
After advanced analysis on natural language question structure, the question structure can be divided into four parts, they are question context, question entity, question activity and question sentiment. We noted that there are some relations between activity and sentiment. Then, we proposed an automated method to identify related sentiments and use them to expand questions. We try to recommend suitable entities based on the intent of users by analyzing the activity which user want to do and the sentiments which behind the activity. We used the algorithm of question analysis to identify question features. As to the answer structure, it can be divided into context evidence page, entity type, entity activity and entity sentiment summation to match the question structure. We combine the relationship between the question structure and the answer structure to construct Activity-Sentiment-based Entity Ranking Model (ASERM) to improve entity search.
Experiment result shows that our proposed method ASERM can help user to get entity list which matched their intent. And it shows ASERM really can enhance performance in entity search.

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