對軟體旅遊代理人來說，推薦合適的旅遊行程給特定的使用者並不是一件容易的事；除了必須滿足使用者的喜好與特殊需求外，旅遊代理人還得確保其行程能夠滿足許多空間的、時間的、外在環境的限制，例如：旅遊景點的開放時間、收費、住宿旅館是否已客滿等等。傳統的推薦方法，大部分都要求使用者先表達他對各旅遊選項的偏好，系統再根據協同式（collaborative recommendation）或以內容為基礎（content-based recommendation）的方法推薦旅遊行程。然而，旅遊這個領域是相當複雜，使用者通常無法在一開始就完完全全地決定他對所有選項的偏好，除非他對這次旅程目的地的有更進一步的瞭解。因此我們認為，未與使用者充分溝通的情況下，旅遊代理人不能獨斷的決定一個「好」的旅遊行程；與使用者的溝通與協調才是旅遊推薦中非常必要的一點。
本篇論文中，我們最感興趣的是旅遊代理人如何以對話與協商的方式來推薦旅遊行程，最後產生出一個任人滿意的結果出來。我們將從滿足使用者偏好與滿足領域限制（domain constraint）的方向入手，由此探討用如何以協商的方式來推薦旅遊行程。而驅動旅遊代理人產生對話與協商的最主因，則正是為了化解逾越限制（resolution of constraint violation）。

Recommending a good trip plan for a particular traveler is often not a trivial task for a travel agent. A travel agent has to satisfy not only the customer’s personal preferences and constraints, but also the complex spatial, temporal, physical constraints and cost imposed by the transportation methods among visiting spots and various environmental supports such as the availability of hotels. In traditional recommendation mechanisms, users are required to express their preferences for many aspects of a trip. Then the system can recommend a trip plan by a collaborative method or a content-based method. However, a traveler may not often express clearly his or her preferences over a trip plan at the outset unless they get more information about the visiting destinations or some details about the trip. Therefore, a travel agent alone cannot always decide a satisfactory trip plan for a traveler without the involvement of the traveler. Communication and negotiation with the traveler becomes a necessary discipline to recommend a trip plan for the traveler.
In this thesis, we are in particular interested in understanding how a travel agent could conduct such kinds of recommendation and negotiation dialogues with the user and come out with a satisfactory trip plan for the user. We focus on the techniques of recommendation by negotiation with the user and by satisfying user’s personal preferences and domain constraints of various kinds. The recommendation and negotiation dialogue of a travel agent is primarily driven by the mechanisms of resolution of constraint violation.

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