面對網路資源檢索結果往往過多的問題，如何將當中最相關的資訊優先排 序在最前面，讓使用者優先看到，以節省其瀏覽所有檢索結果的時間，是目前 系統開發者選擇相關排序（Relevance ranking)作爲檢索結果排序的原因。目 前大部分的資訊檢索系統係以相似性而非相關性作爲檢索結果排序基礎，但使 用者係判斷檢索結果相關與否之唯一裁判者，爲此，相關排序的發展也開始將 使用者的相關判斷及資訊使用行爲作爲改善相關排序效能之努力方向，希望能 針對使用者的不同需求提供更個人化的資訊服務。

The retrieval results of a web search are usually very large. Therefore, the information retrieval system usually uses the relevance ranking to ranking retrieval results, provideing users a saving-time way to look through the searching results and obtain the most relevant documents. Currently, most information retrieval systems use similarity instead of relevance to rank the searching results. However, the end-user is the one to determine the relevance of retrieval results, so many researchers consider the user's relevance requirement and information behavior are the way to improve the effectives of relevance ranking. The objective of relevance ranking is to provide personalized information service for users.